The Event Horizon Telescope (EHT) collaboration has produced the first resolved images of M87*, the supermassive black hole at the centre of the elliptical galaxy M87. As both technology and analysis pipelines improve, it will soon become possible to produce spectral index maps of black hole accretion flows on event horizon scales. In this work, we predict spectral index maps of both M87* and Sgr A* by applying the general relativistic radiative transfer (GRRT) code {\sc ipole} to a suite of general relativistic magnetohydrodynamic (GRMHD) simulations. We analytically explore how the spectral index increases with increasing magnetic field strength, electron temperature, and optical depth. Consequently, spectral index maps grow more negative with increasing radius in almost all models, since all of these quantities tend to be maximized near the event horizon. Additionally, photon ring geodesics exhibit more positive spectral indices, since they sample the innermost regions of the accretion flow with the most extreme plasma conditions. Spectral index maps are sensitive to highly uncertain plasma heating prescriptions (the electron temperature and distribution function). However, if our understanding of these aspects of plasma physics can be tightened, even the spatially unresolved spectral index around 230 GHz can be used to discriminate between models. In particular, Standard and Normal Evolution (SANE) flows tend to exhibit more negative spectral indices than Magnetically Arrested Disk (MAD) flows due to differences in the characteristic magnetic field strength and temperature of emitting plasma.
AU - BT - Monthly Notices of the Royal Astronomical Society LA - eng N2 -The Event Horizon Telescope (EHT) collaboration has produced the first resolved images of M87*, the supermassive black hole at the centre of the elliptical galaxy M87. As both technology and analysis pipelines improve, it will soon become possible to produce spectral index maps of black hole accretion flows on event horizon scales. In this work, we predict spectral index maps of both M87* and Sgr A* by applying the general relativistic radiative transfer (GRRT) code {\sc ipole} to a suite of general relativistic magnetohydrodynamic (GRMHD) simulations. We analytically explore how the spectral index increases with increasing magnetic field strength, electron temperature, and optical depth. Consequently, spectral index maps grow more negative with increasing radius in almost all models, since all of these quantities tend to be maximized near the event horizon. Additionally, photon ring geodesics exhibit more positive spectral indices, since they sample the innermost regions of the accretion flow with the most extreme plasma conditions. Spectral index maps are sensitive to highly uncertain plasma heating prescriptions (the electron temperature and distribution function). However, if our understanding of these aspects of plasma physics can be tightened, even the spatially unresolved spectral index around 230 GHz can be used to discriminate between models. In particular, Standard and Normal Evolution (SANE) flows tend to exhibit more negative spectral indices than Magnetically Arrested Disk (MAD) flows due to differences in the characteristic magnetic field strength and temperature of emitting plasma.
T1 - Probing Plasma Physics with Spectral Index Maps of Accreting Black Holes on Event Horizon Scales T2 - Monthly Notices of the Royal Astronomical Society TI - Probing Plasma Physics with Spectral Index Maps of Accreting Black Holes on Event Horizon Scales UR - https://arxiv.org/abs/2202.02408 ER - TY - JOUR A1 - Joshua Yao-Yu Lin A1 - Dominic W. Pesce A1 - George N. Wong A1 - Ajay Uppili Arasanipalai A1 - Ben S. Prather A1 - Charles F. Gammie AB -The Event Horizon Telescope (EHT) recently released the first horizon-scale images of the black hole in M87. Combined with other astronomical data, these images constrain the mass and spin of the hole as well as the accretion rate and magnetic flux trapped on the hole. An important question for the EHT is how well key parameters, such as trapped magnetic flux and the associated disk models, can be extracted from present and future EHT VLBI data products. The process of modeling visibilities and analyzing them is complicated by the fact that the data are sparsely sampled in the Fourier domain while most of the theory/simulation is constructed in the image domain. Here we propose a data-driven approach to analyze complex visibilities and closure quantities for radio interferometric data with neural networks. Using mock interferometric data, we show that our neural networks are able to infer the accretion state as either high magnetic flux (MAD) or low magnetic flux (SANE), suggesting that it is possible to perform parameter extraction directly in the visibility domain without image reconstruction. We have applied VLBInet to real M87 EHT data taken on four different days in 2017 (April 5, 6, 10, 11), and our neural networks give a score prediction 0.52, 0.4, 0.43, 0.76 for each day, with an average score 0.53, which shows no significant indication for the data to lean toward either the MAD or SANE state.
AU - LA - eng N2 -The Event Horizon Telescope (EHT) recently released the first horizon-scale images of the black hole in M87. Combined with other astronomical data, these images constrain the mass and spin of the hole as well as the accretion rate and magnetic flux trapped on the hole. An important question for the EHT is how well key parameters, such as trapped magnetic flux and the associated disk models, can be extracted from present and future EHT VLBI data products. The process of modeling visibilities and analyzing them is complicated by the fact that the data are sparsely sampled in the Fourier domain while most of the theory/simulation is constructed in the image domain. Here we propose a data-driven approach to analyze complex visibilities and closure quantities for radio interferometric data with neural networks. Using mock interferometric data, we show that our neural networks are able to infer the accretion state as either high magnetic flux (MAD) or low magnetic flux (SANE), suggesting that it is possible to perform parameter extraction directly in the visibility domain without image reconstruction. We have applied VLBInet to real M87 EHT data taken on four different days in 2017 (April 5, 6, 10, 11), and our neural networks give a score prediction 0.52, 0.4, 0.43, 0.76 for each day, with an average score 0.53, which shows no significant indication for the data to lean toward either the MAD or SANE state.
T1 - VLBInet: Radio Interferometry Data Classification for EHT with Neural Networks TI - VLBInet: Radio Interferometry Data Classification for EHT with Neural Networks UR - https://arxiv.org/abs/2110.07185 ER - TY - JOUR A1 - He Sun A1 - Katherine L. Bouman A1 - Paul Tiede A1 - Jason J. Wang A1 - Sarah Blunt A1 - Dimitri Mawet AB -Inference is crucial in modern astronomical research, where hidden astrophysical features and patterns are often estimated from indirect and noisy measurements. Inferring the posterior of hidden features, conditioned on the observed measurements, is essential for understanding the uncertainty of results and downstream scientific interpretations. Traditional approaches for posterior estimation include sampling-based methods and variational inference. However, sampling-based methods are typically slow for high-dimensional inverse problems, while variational inference often lacks estimation accuracy. In this paper, we propose alpha-DPI, a deep learning framework that first learns an approximate posterior using alpha-divergence variational inference paired with a generative neural network, and then produces more accurate posterior samples through importance re-weighting of the network samples. It inherits strengths from both sampling and variational inference methods: it is fast, accurate, and scalable to high-dimensional problems. We apply our approach to two high-impact astronomical inference problems using real data: exoplanet astrometry and black hole feature extraction.
AU - LA - eng N2 -Inference is crucial in modern astronomical research, where hidden astrophysical features and patterns are often estimated from indirect and noisy measurements. Inferring the posterior of hidden features, conditioned on the observed measurements, is essential for understanding the uncertainty of results and downstream scientific interpretations. Traditional approaches for posterior estimation include sampling-based methods and variational inference. However, sampling-based methods are typically slow for high-dimensional inverse problems, while variational inference often lacks estimation accuracy. In this paper, we propose alpha-DPI, a deep learning framework that first learns an approximate posterior using alpha-divergence variational inference paired with a generative neural network, and then produces more accurate posterior samples through importance re-weighting of the network samples. It inherits strengths from both sampling and variational inference methods: it is fast, accurate, and scalable to high-dimensional problems. We apply our approach to two high-impact astronomical inference problems using real data: exoplanet astrometry and black hole feature extraction.
T1 - alpha-Deep Probabilistic Inference (alpha-DPI): efficient uncertainty quantification from exoplanet astrometry to black hole feature extraction TI - alpha-Deep Probabilistic Inference (alpha-DPI): efficient uncertainty quantification from exoplanet astrometry to black hole feature extraction UR - https://arxiv.org/abs/2201.08506 ER - TY - JOUR A1 - et Kaushik Satapathy al. AB - The black hole images obtained with the Event Horizon Telescope (EHT) are expected to be variable at the dynamical timescale near their horizons. For the black hole at the center of the M87 galaxy, this timescale (5–61 days) is comparable to the 6 day extent of the 2017 EHT observations. Closure phases along baseline triangles are robust interferometric observables that are sensitive to the expected structural changes of the images but are free of station-based atmospheric and instrumental errors. We explored the day-to-day variability in closure-phase measurements on all six linearly independent nontrivial baseline triangles that can be formed from the 2017 observations. We showed that three triangles exhibit very low day-to-day variability, with a dispersion of ∼3°–5°. The only triangles that exhibit substantially higher variability (∼90°–180°) are the ones with baselines that cross the visibility amplitude minima on the u–v plane, as expected from theoretical modeling. We used two sets of general relativistic magnetohydrodynamic simulations to explore the dependence of the predicted variability on various black hole and accretion-flow parameters. We found that changing the magnetic field configuration, electron temperature model, or black hole spin has a marginal effect on the model consistency with the observed level of variability. On the other hand, the most discriminating image characteristic of models is the fractional width of the bright ring of emission. Models that best reproduce the observed small level of variability are characterized by thin ring-like images with structures dominated by gravitational lensing effects and thus least affected by turbulence in the accreting plasmas. AU - BT - The Astrophysical Journal IS - 1 LA - eng N2 - The black hole images obtained with the Event Horizon Telescope (EHT) are expected to be variable at the dynamical timescale near their horizons. For the black hole at the center of the M87 galaxy, this timescale (5–61 days) is comparable to the 6 day extent of the 2017 EHT observations. Closure phases along baseline triangles are robust interferometric observables that are sensitive to the expected structural changes of the images but are free of station-based atmospheric and instrumental errors. We explored the day-to-day variability in closure-phase measurements on all six linearly independent nontrivial baseline triangles that can be formed from the 2017 observations. We showed that three triangles exhibit very low day-to-day variability, with a dispersion of ∼3°–5°. The only triangles that exhibit substantially higher variability (∼90°–180°) are the ones with baselines that cross the visibility amplitude minima on the u–v plane, as expected from theoretical modeling. We used two sets of general relativistic magnetohydrodynamic simulations to explore the dependence of the predicted variability on various black hole and accretion-flow parameters. We found that changing the magnetic field configuration, electron temperature model, or black hole spin has a marginal effect on the model consistency with the observed level of variability. On the other hand, the most discriminating image characteristic of models is the fractional width of the bright ring of emission. Models that best reproduce the observed small level of variability are characterized by thin ring-like images with structures dominated by gravitational lensing effects and thus least affected by turbulence in the accreting plasmas. PY - 2022 EP - 13 T1 - The Variability of the Black Hole Image in M87 at the Dynamical Timescale T2 - The Astrophysical Journal TI - The Variability of the Black Hole Image in M87 at the Dynamical Timescale UR - https://doi.org/10.3847/1538-4357/ac332e VL - 925 Y1 - 2022 ER - TY - JOUR A1 - George N. Wong A1 - Ben S. Prather A1 - Vedant Dhruv A1 - Benjamin R. Ryan A1 - Monika Mościbrodzka A1 - Chi-Kwan Chan A1 - Abhishek V. Joshi A1 - Ricardo Yarza A1 - Angelo Ricarte A1 - Hotaka Shiokawa A1 - Joshua C. Dolence A1 - Scott C. Noble A1 - Jonathan C. McKinney A1 - Charles F. Gammie AB - The Event Horizon Telescope (EHT) has released analyses of reconstructed images of horizon-scale millimeter emission near the supermassive black hole at the center of the M87 galaxy. Parts of the analyses made use of a large library of synthetic black hole images and spectra, which were produced using numerical general relativistic magnetohydrodynamics fluid simulations and polarized ray tracing. In this article, we describe the PATOKA pipeline, which was used to generate the Illinois contribution to the EHT simulation library. We begin by describing the relevant accretion systems and radiative processes. We then describe the details of the three numerical codes we use, iharm, ipole, and igrmonty, paying particular attention to differences between the current generation of the codes and the originally published versions. Finally, we provide a brief overview of simulated data as produced by PATOKA and conclude with a discussion of limitations and future directions. AU - BT - The Astrophysical Journal Supplement Series IS - 2, 64 LA - eng N2 - The Event Horizon Telescope (EHT) has released analyses of reconstructed images of horizon-scale millimeter emission near the supermassive black hole at the center of the M87 galaxy. Parts of the analyses made use of a large library of synthetic black hole images and spectra, which were produced using numerical general relativistic magnetohydrodynamics fluid simulations and polarized ray tracing. In this article, we describe the PATOKA pipeline, which was used to generate the Illinois contribution to the EHT simulation library. We begin by describing the relevant accretion systems and radiative processes. We then describe the details of the three numerical codes we use, iharm, ipole, and igrmonty, paying particular attention to differences between the current generation of the codes and the originally published versions. Finally, we provide a brief overview of simulated data as produced by PATOKA and conclude with a discussion of limitations and future directions. PY - 2022 T1 - PATOKA: Simulating Electromagnetic Observables of Black Hole Accretion T2 - The Astrophysical Journal Supplement Series TI - PATOKA: Simulating Electromagnetic Observables of Black Hole Accretion UR - https://doi.org/10.3847/1538-4365/ac582e VL - 259 Y1 - 2022 ER - TY - JOUR A1 - Daniel C. M. Palumbo A1 - George N. Wong AB - The Event Horizon Telescope (EHT) recently released the first linearly polarized images of the accretion flow around the supermassive black hole Messier 87*, hereafter M87*. The spiraling polarization pattern found in the EHT images favored magnetically arrested disks as the explanation for the EHT image. With next-generation improvements to very long baseline interferometry on the horizon, understanding similar polarized features in the highly lensed structure known as the "photon ring," where photons make multiple half orbits about the black hole before reaching the observer, will be critical to the analysis of future images. Recent work has indicated that this image region may be depolarized relative to more direct emission. We expand this observation by decomposing photon half orbits in the EHT library of simulated images of the M 87* accretion system and find that images of magnetically arrested disk simulations show a relative depolarization of the photon ring attributable to destructive interference of oppositely spiraling electric field vectors; this antisymmetry, which arises purely from strong gravitational lensing, can produce up to ∼50% depolarization in the photon ring region with respect to the direct image. In systems that are not magnetically arrested and with the exception of systems with high spin and ions and electrons of equal temperature, we find that highly lensed indirect subimages are almost completely depolarized, causing a modest depolarization of the photon ring region in the complete image. We predict that next-generation EHT observations of M 87* polarization should jointly constrain the black hole spin and the underlying emission and magnetic field geometry. AU - BT - The Astrophysical Journal LA - eng N2 - The Event Horizon Telescope (EHT) recently released the first linearly polarized images of the accretion flow around the supermassive black hole Messier 87*, hereafter M87*. The spiraling polarization pattern found in the EHT images favored magnetically arrested disks as the explanation for the EHT image. With next-generation improvements to very long baseline interferometry on the horizon, understanding similar polarized features in the highly lensed structure known as the "photon ring," where photons make multiple half orbits about the black hole before reaching the observer, will be critical to the analysis of future images. Recent work has indicated that this image region may be depolarized relative to more direct emission. We expand this observation by decomposing photon half orbits in the EHT library of simulated images of the M 87* accretion system and find that images of magnetically arrested disk simulations show a relative depolarization of the photon ring attributable to destructive interference of oppositely spiraling electric field vectors; this antisymmetry, which arises purely from strong gravitational lensing, can produce up to ∼50% depolarization in the photon ring region with respect to the direct image. In systems that are not magnetically arrested and with the exception of systems with high spin and ions and electrons of equal temperature, we find that highly lensed indirect subimages are almost completely depolarized, causing a modest depolarization of the photon ring region in the complete image. We predict that next-generation EHT observations of M 87* polarization should jointly constrain the black hole spin and the underlying emission and magnetic field geometry. PY - 2022 EP - 49 T1 - Photon Ring Symmetries in Simulated Linear Polarization Images of Messier 87* T2 - The Astrophysical Journal TI - Photon Ring Symmetries in Simulated Linear Polarization Images of Messier 87* UR - https://doi.org/10.3847/1538-4357/ac59b4 VL - 929 Y1 - 2022 ER - TY - JOUR A1 - Lia Medeiros A1 - Chi-Kwan Chan A1 - Ramesh Narayan A1 - Feryal Özel A1 - Dimitrios Psaltis AB - The Event Horizon Telescope recently captured images of the supermassive black hole in the center of the M87 galaxy, which shows a ring-like emission structure with the south side only slightly brighter than the north side. This relatively weak asymmetry in the brightness profile along the ring has been interpreted as a consequence of the low inclination of the observer (around 17° for M87), which suppresses the Doppler beaming and boosting effects that might otherwise be expected due to the nearly relativistic velocities of the orbiting plasma. In this work, we use a large suite of general relativistic magnetohydrodynamic simulations to reassess the validity of this argument. By constructing explicit counterexamples, we show that low inclination is a sufficient but not necessary condition for images to have low brightness asymmetry. Accretion flow models with high accumulated magnetic flux close to the black hole horizon (the so-called magnetically arrested disks) and low black hole spins have angular velocities that are substantially smaller than the orbital velocities of test particles at the same location. As a result, such models can produce images with low brightness asymmetry even when viewed edge on. AU - BT - The Astrophysical Journal LA - eng N2 - The Event Horizon Telescope recently captured images of the supermassive black hole in the center of the M87 galaxy, which shows a ring-like emission structure with the south side only slightly brighter than the north side. This relatively weak asymmetry in the brightness profile along the ring has been interpreted as a consequence of the low inclination of the observer (around 17° for M87), which suppresses the Doppler beaming and boosting effects that might otherwise be expected due to the nearly relativistic velocities of the orbiting plasma. In this work, we use a large suite of general relativistic magnetohydrodynamic simulations to reassess the validity of this argument. By constructing explicit counterexamples, we show that low inclination is a sufficient but not necessary condition for images to have low brightness asymmetry. Accretion flow models with high accumulated magnetic flux close to the black hole horizon (the so-called magnetically arrested disks) and low black hole spins have angular velocities that are substantially smaller than the orbital velocities of test particles at the same location. As a result, such models can produce images with low brightness asymmetry even when viewed edge on. PY - 2022 EP - 46 T1 - Brightness Asymmetry of Black Hole Images as a Probe of Observer Inclination T2 - The Astrophysical Journal TI - Brightness Asymmetry of Black Hole Images as a Probe of Observer Inclination VL - 924 Y1 - 2022 ER - TY - JOUR A1 - Joseph Farah A1 - Peter Galison A1 - Kazunori Akiyama A1 - Katherine L. Bouman A1 - Geoffrey C. Bower A1 - Andrew Chael A1 - Antonio Fuentes A1 - José L. Gómez A1 - Mareki Honma A1 - Michael D. Johnson A1 - Yutaro Kofuji A1 - Daniel P. Marrone A1 - Kotaro Moriyama A1 - Ramesh Narayan A1 - Dominic W. Pesce A1 - Paul Tiede A1 - Maciek Wielgus A1 - Guang-Yao Zhao A1 - The Event Horizon Telescope Collaboration AB - Recent developments in very long baseline interferometry (VLBI) have made it possible for the Event Horizon Telescope (EHT) to resolve the innermost accretion flows of the largest supermassive black holes on the sky. The sparse nature of the EHT's (u, v)-coverage presents a challenge when attempting to resolve highly time-variable sources. We demonstrate that the changing (u, v)-coverage of the EHT can contain regions of time over the course of a single observation that facilitate dynamical imaging. These optimal time regions typically have projected baseline distributions that are approximately angularly isotropic and radially homogeneous. We derive a metric of coverage quality based on baseline isotropy and density that is capable of ranking array configurations by their ability to produce accurate dynamical reconstructions. We compare this metric to existing metrics in the literature and investigate their utility by performing dynamical reconstructions on synthetic data from simulated EHT observations of sources with simple orbital variability. We then use these results to make recommendations for imaging the 2017 EHT Sgr A* data set. AU - BT - The Astrophysical Journal Letters IS - L18 LA - eng N2 - Recent developments in very long baseline interferometry (VLBI) have made it possible for the Event Horizon Telescope (EHT) to resolve the innermost accretion flows of the largest supermassive black holes on the sky. The sparse nature of the EHT's (u, v)-coverage presents a challenge when attempting to resolve highly time-variable sources. We demonstrate that the changing (u, v)-coverage of the EHT can contain regions of time over the course of a single observation that facilitate dynamical imaging. These optimal time regions typically have projected baseline distributions that are approximately angularly isotropic and radially homogeneous. We derive a metric of coverage quality based on baseline isotropy and density that is capable of ranking array configurations by their ability to produce accurate dynamical reconstructions. We compare this metric to existing metrics in the literature and investigate their utility by performing dynamical reconstructions on synthetic data from simulated EHT observations of sources with simple orbital variability. We then use these results to make recommendations for imaging the 2017 EHT Sgr A* data set. PY - 2022 SP - 1 EP - 21 T1 - Selective Dynamical Imaging of Interferometric Data T2 - The Astrophysical Journal Letters TI - Selective Dynamical Imaging of Interferometric Data UR - https://doi.org/10.3847/2041-8213/ac6615 VL - 930 Y1 - 2022 ER - TY - JOUR A1 - Maciek Wielgus A1 - Nicola Marchili A1 - Iván Martí-Vidal A1 - Garrett K. Keating A1 - Venkatessh Ramakrishnan A1 - Paul Tiede A1 - Sara Issaoun A1 - Joey Neilsen A1 - Michael A. Nowak A1 - Lindy Blackburn A1 - Ciriaco Goddi A1 - Daryl Haggard A1 - Daeyoung Lee A1 - Monika Moscibrodzka A1 - Alexandra J. Tetarenko A1 - Geoffrey C. Bower A1 - Chi-Kwan Chan A1 - Koushik Chatterjee A1 - Paul M. Chesler A1 - Jason Dexter A1 - Sheperd S. Doeleman A1 - Boris Georgiev A1 - Mark Gurwell A1 - Michael D. Johnson A1 - Daniel P. Marrone A1 - Alejandro Mus A1 - Dimitrios Psaltis A1 - Gunther Witzel A1 - The Event Horizon Telescope Collaboration AB -The Event Horizon Telescope (EHT) observed the compact radio source, Sagittarius A* (Sgr A*), in the Galactic Center on 2017 April 5-11 in the 1.3 mm wavelength band. At the same time, interferometric array data from the Atacama Large Millimeter/submillimeter Array and the Submillimeter Array were collected, providing Sgr A* light curves simultaneous with the EHT observations. These data sets, complementing the EHT very long baseline interferometry, are characterized by a cadence and signal-to-noise ratio previously unattainable for Sgr A* at millimeter wavelengths, and they allow for the investigation of source variability on timescales as short as a minute. While most of the light curves correspond to a low variability state of Sgr A*, the April 11 observations follow an X-ray flare and exhibit strongly enhanced variability. All of the light curves are consistent with a red-noise process, with a power spectral density (PSD) slope measured to be between -2 and -3 on timescales between 1 minute and several hours. Our results indicate a steepening of the PSD slope for timescales shorter than 0.3 hr. The spectral energy distribution is flat at 220 GHz, and there are no time lags between the 213 and 229 GHz frequency bands, suggesting low optical depth for the event horizon scale source. We characterize Sgr A*'s variability, highlighting the different behavior observed just after the X-ray flare, and use Gaussian process modeling to extract a decorrelation timescale and a PSD slope. We also investigate the systematic calibration uncertainties by analyzing data from independent data reduction pipelines.
AU - BT - The Astrophysical Journal Letters IS - L19 LA - eng N2 -The Event Horizon Telescope (EHT) observed the compact radio source, Sagittarius A* (Sgr A*), in the Galactic Center on 2017 April 5-11 in the 1.3 mm wavelength band. At the same time, interferometric array data from the Atacama Large Millimeter/submillimeter Array and the Submillimeter Array were collected, providing Sgr A* light curves simultaneous with the EHT observations. These data sets, complementing the EHT very long baseline interferometry, are characterized by a cadence and signal-to-noise ratio previously unattainable for Sgr A* at millimeter wavelengths, and they allow for the investigation of source variability on timescales as short as a minute. While most of the light curves correspond to a low variability state of Sgr A*, the April 11 observations follow an X-ray flare and exhibit strongly enhanced variability. All of the light curves are consistent with a red-noise process, with a power spectral density (PSD) slope measured to be between -2 and -3 on timescales between 1 minute and several hours. Our results indicate a steepening of the PSD slope for timescales shorter than 0.3 hr. The spectral energy distribution is flat at 220 GHz, and there are no time lags between the 213 and 229 GHz frequency bands, suggesting low optical depth for the event horizon scale source. We characterize Sgr A*'s variability, highlighting the different behavior observed just after the X-ray flare, and use Gaussian process modeling to extract a decorrelation timescale and a PSD slope. We also investigate the systematic calibration uncertainties by analyzing data from independent data reduction pipelines.
PY - 2022 SP - 1 EP - 32 T1 - Millimeter Light Curves of Sagittarius A* Observed during the 2017 Event Horizon Telescope Campaign T2 - The Astrophysical Journal Letters TI - Millimeter Light Curves of Sagittarius A* Observed during the 2017 Event Horizon Telescope Campaign UR - https://doi.org/10.3847/2041-8213/ac6428 VL - 930 Y1 - 2022 ER - TY - JOUR A1 - Boris Georgiev A1 - Dominic W. Pesce A1 - Avery E. Broderick A1 - Vedant Dhruv A1 - Charles F. Gammie A1 - Chi-Kwan Chan A1 - Koushik Chatterjee A1 - Razieh Emami A1 - Yosuke Mizuno A1 - Roman Gold A1 - Christian M. Fromm A1 - Angelo Ricarte A1 - Doosoo Yoon A1 - Abhishek V. Joshi A1 - Ben Prather A1 - Alejandro Cruz-Osorio A1 - Michael D. Johnson A1 - Oliver Porth A1 - Héctor Olivares A1 - Ziri Younsi A1 - Luciano Rezzolla A1 - Jesse Vos A1 - Richard Qiu A1 - Antonios Nathanail A1 - Ramesh Narayan A1 - Andrew Chael A1 - Richard Anantua A1 - Monika Moscibrodzka A1 - The Event Horizon Telescope Collaboration AB -We present a framework for characterizing the spatiotemporal power spectrum of the variability expected from the horizon-scale emission structure around supermassive black holes, and we apply this framework to a library of general relativistic magnetohydrodynamic (GRMHD) simulations and associated general relativistic ray-traced images relevant for Event Horizon Telescope (EHT) observations of Sgr A*. We find that the variability power spectrum is generically a red-noise process in both the temporal and spatial dimensions, with the peak in power occurring on the longest timescales and largest spatial scales. When both the time-averaged source structure and the spatially integrated light-curve variability are removed, the residual power spectrum exhibits a universal broken power-law behavior. On small spatial frequencies, the residual power spectrum rises as the square of the spatial frequency and is proportional to the variance in the centroid of emission. Beyond some peak in variability power, the residual power spectrum falls as that of the time-averaged source structure, which is similar across simulations; this behavior can be naturally explained if the variability arises from a multiplicative random field that has a steeper high-frequency power-law index than that of the time-averaged source structure. We briefly explore the ability of power spectral variability studies to constrain physical parameters relevant for the GRMHD simulations, which can be scaled to provide predictions for black holes in a range of systems in the optically thin regime. We present specific expectations for the behavior of the M87* and Sgr A* accretion flows as observed by the EHT.
AU - BT - The Astrophysical Journal Letters IS - L20 LA - eng N2 -We present a framework for characterizing the spatiotemporal power spectrum of the variability expected from the horizon-scale emission structure around supermassive black holes, and we apply this framework to a library of general relativistic magnetohydrodynamic (GRMHD) simulations and associated general relativistic ray-traced images relevant for Event Horizon Telescope (EHT) observations of Sgr A*. We find that the variability power spectrum is generically a red-noise process in both the temporal and spatial dimensions, with the peak in power occurring on the longest timescales and largest spatial scales. When both the time-averaged source structure and the spatially integrated light-curve variability are removed, the residual power spectrum exhibits a universal broken power-law behavior. On small spatial frequencies, the residual power spectrum rises as the square of the spatial frequency and is proportional to the variance in the centroid of emission. Beyond some peak in variability power, the residual power spectrum falls as that of the time-averaged source structure, which is similar across simulations; this behavior can be naturally explained if the variability arises from a multiplicative random field that has a steeper high-frequency power-law index than that of the time-averaged source structure. We briefly explore the ability of power spectral variability studies to constrain physical parameters relevant for the GRMHD simulations, which can be scaled to provide predictions for black holes in a range of systems in the optically thin regime. We present specific expectations for the behavior of the M87* and Sgr A* accretion flows as observed by the EHT.
PY - 2022 SP - 1 EP - 32 T1 - A Universal Power-law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows T2 - The Astrophysical Journal Letters TI - A Universal Power-law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows VL - 930 Y1 - 2022 ER - TY - JOUR A1 - Avery E. Broderick A1 - Roman Gold A1 - Boris Georgiev A1 - Dominic W. Pesce A1 - Paul Tiede A1 - Chunchong Ni A1 - Kotaro Moriyama A1 - The Event Horizon Telescope Collaboration AB - The extraordinary physical resolution afforded by the Event Horizon Telescope has opened a window onto the astrophysical phenomena unfolding on horizon scales in two known black holes, M87* and Sgr A*. However, with this leap in resolution has come a new set of practical complications. Sgr A* exhibits intraday variability that violates the assumptions underlying Earth aperture synthesis, limiting traditional image reconstruction methods to short timescales and data sets with very sparse (u, v) coverage. We present a new set of tools to detect and mitigate this variability. We develop a data-driven, model-agnostic procedure to detect and characterize the spatial structure of intraday variability. This method is calibrated against a large set of mock data sets, producing an empirical estimator of the spatial power spectrum of the brightness fluctuations. We present a novel Bayesian noise modeling algorithm that simultaneously reconstructs an average image and statistical measure of the fluctuations about it using a parameterized form for the excess variance in the complex visibilities not otherwise explained by the statistical errors. These methods are validated using a variety of simulated data, including general relativistic magnetohydrodynamic simulations appropriate for Sgr A* and M87*. We find that the reconstructed source structure and variability are robust to changes in the underlying image model. We apply these methods to the 2017 EHT observations of M87*, finding evidence for variability across the EHT observing campaign. The variability mitigation strategies presented are widely applicable to very long baseline interferometry observations of variable sources generally, for which they provide a data-informed averaging procedure and natural characterization of inter-epoch image consistency. AU - BT - The Astrophysical Journal Letters IS - L21 LA - eng N2 - The extraordinary physical resolution afforded by the Event Horizon Telescope has opened a window onto the astrophysical phenomena unfolding on horizon scales in two known black holes, M87* and Sgr A*. However, with this leap in resolution has come a new set of practical complications. Sgr A* exhibits intraday variability that violates the assumptions underlying Earth aperture synthesis, limiting traditional image reconstruction methods to short timescales and data sets with very sparse (u, v) coverage. We present a new set of tools to detect and mitigate this variability. We develop a data-driven, model-agnostic procedure to detect and characterize the spatial structure of intraday variability. This method is calibrated against a large set of mock data sets, producing an empirical estimator of the spatial power spectrum of the brightness fluctuations. We present a novel Bayesian noise modeling algorithm that simultaneously reconstructs an average image and statistical measure of the fluctuations about it using a parameterized form for the excess variance in the complex visibilities not otherwise explained by the statistical errors. These methods are validated using a variety of simulated data, including general relativistic magnetohydrodynamic simulations appropriate for Sgr A* and M87*. We find that the reconstructed source structure and variability are robust to changes in the underlying image model. We apply these methods to the 2017 EHT observations of M87*, finding evidence for variability across the EHT observing campaign. The variability mitigation strategies presented are widely applicable to very long baseline interferometry observations of variable sources generally, for which they provide a data-informed averaging procedure and natural characterization of inter-epoch image consistency. PY - 2022 SP - 1 EP - 30 T1 - Characterizing and Mitigating Intraday Variability: Reconstructing Source Structure in Accreting Black Holes with mm-VLBI T2 - The Astrophysical Journal Letters TI - Characterizing and Mitigating Intraday Variability: Reconstructing Source Structure in Accreting Black Holes with mm-VLBI VL - 930 Y1 - 2022 ER - TY - JOUR A1 - The Event Horizon Telescope Collaboration AB -We present the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength of λ = 1.3 mm. The EHT data resolve a compact emission region with intrahour variability. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of 51.8 ± 2.3 μas (68% credible interval). The ring has modest azimuthal brightness asymmetry and a comparatively dim interior. Using a large suite of numerical simulations, we demonstrate that the EHT images of Sgr A* are consistent with the expected appearance of a Kerr black hole with mass ~4 × 106 M⊙, which is inferred to exist at this location based on previous infrared observations of individual stellar orbits, as well as maser proper-motion studies. Our model comparisons disfavor scenarios where the black hole is viewed at high inclination (i > 50°), as well as nonspinning black holes and those with retrograde accretion disks. Our results provide direct evidence for the presence of a supermassive black hole at the center of the Milky Way, and for the first time we connect the predictions from dynamical measurements of stellar orbits on scales of 103-105 gravitational radii to event-horizon-scale images and variability. Furthermore, a comparison with the EHT results for the supermassive black hole M87* shows consistency with the predictions of general relativity spanning over three orders of magnitude in central mass.
AU - BT - The Astrophysical Journal Letters IS - L12 LA - eng N2 -We present the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength of λ = 1.3 mm. The EHT data resolve a compact emission region with intrahour variability. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of 51.8 ± 2.3 μas (68% credible interval). The ring has modest azimuthal brightness asymmetry and a comparatively dim interior. Using a large suite of numerical simulations, we demonstrate that the EHT images of Sgr A* are consistent with the expected appearance of a Kerr black hole with mass ~4 × 106 M⊙, which is inferred to exist at this location based on previous infrared observations of individual stellar orbits, as well as maser proper-motion studies. Our model comparisons disfavor scenarios where the black hole is viewed at high inclination (i > 50°), as well as nonspinning black holes and those with retrograde accretion disks. Our results provide direct evidence for the presence of a supermassive black hole at the center of the Milky Way, and for the first time we connect the predictions from dynamical measurements of stellar orbits on scales of 103-105 gravitational radii to event-horizon-scale images and variability. Furthermore, a comparison with the EHT results for the supermassive black hole M87* shows consistency with the predictions of general relativity spanning over three orders of magnitude in central mass.
PY - 2022 T1 - First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way T2 - The Astrophysical Journal Letters TI - First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way UR - https://doi.org/10.3847/2041-8213/ac6674 VL - 930 Y1 - 2022 ER - TY - JOUR A1 - The Event Horizon Telescope Collaboration AB -We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5-11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of ~50 μas, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*'s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior.
AU - BT - The Astrophysical Journal Letters IS - L13 LA - eng N2 -We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5-11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of ~50 μas, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*'s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior.
PY - 2022 T1 - First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration T2 - The Astrophysical Journal Letters TI - First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration VL - 930 Y1 - 2022 ER - TY - JOUR A1 - The Event Horizon Telescope Collaboration AB -We present the first event-horizon-scale images and spatiotemporal analysis of Sgr A* taken with the Event Horizon Telescope in 2017 April at a wavelength of 1.3 mm. Imaging of Sgr A* has been conducted through surveys over a wide range of imaging assumptions using the classical CLEAN algorithm, regularized maximum likelihood methods, and a Bayesian posterior sampling method. Different prescriptions have been used to account for scattering effects by the interstellar medium toward the Galactic center. Mitigation of the rapid intraday variability that characterizes Sgr A* has been carried out through the addition of a "variability noise budget" in the observed visibilities, facilitating the reconstruction of static full-track images. Our static reconstructions of Sgr A* can be clustered into four representative morphologies that correspond to ring images with three different azimuthal brightness distributions and a small cluster that contains diverse nonring morphologies. Based on our extensive analysis of the effects of sparse (u, v)-coverage, source variability, and interstellar scattering, as well as studies of simulated visibility data, we conclude that the Event Horizon Telescope Sgr A* data show compelling evidence for an image that is dominated by a bright ring of emission with a ring diameter of ~50 μas, consistent with the expected "shadow" of a 4 × 106 M ⊙ black hole in the Galactic center located at a distance of 8 kpc.
AU - BT - The Astrophysical Journal Letters IS - L14 LA - eng N2 -We present the first event-horizon-scale images and spatiotemporal analysis of Sgr A* taken with the Event Horizon Telescope in 2017 April at a wavelength of 1.3 mm. Imaging of Sgr A* has been conducted through surveys over a wide range of imaging assumptions using the classical CLEAN algorithm, regularized maximum likelihood methods, and a Bayesian posterior sampling method. Different prescriptions have been used to account for scattering effects by the interstellar medium toward the Galactic center. Mitigation of the rapid intraday variability that characterizes Sgr A* has been carried out through the addition of a "variability noise budget" in the observed visibilities, facilitating the reconstruction of static full-track images. Our static reconstructions of Sgr A* can be clustered into four representative morphologies that correspond to ring images with three different azimuthal brightness distributions and a small cluster that contains diverse nonring morphologies. Based on our extensive analysis of the effects of sparse (u, v)-coverage, source variability, and interstellar scattering, as well as studies of simulated visibility data, we conclude that the Event Horizon Telescope Sgr A* data show compelling evidence for an image that is dominated by a bright ring of emission with a ring diameter of ~50 μas, consistent with the expected "shadow" of a 4 × 106 M ⊙ black hole in the Galactic center located at a distance of 8 kpc.
PY - 2022 T1 - First Sagittarius A* Event Horizon Telescope Results. III. Imaging of the Galactic Center Supermassive Black Hole T2 - The Astrophysical Journal Letters TI - First Sagittarius A* Event Horizon Telescope Results. III. Imaging of the Galactic Center Supermassive Black Hole UR - https://doi.org/10.3847/2041-8213/ac6429 VL - 930 Y1 - 2022 ER - TY - JOUR A1 - The Event Horizon Telescope Collaboration AB -In this paper we quantify the temporal variability and image morphology of the horizon-scale emission from Sgr A*, as observed by the EHT in 2017 April at a wavelength of 1.3 mm. We find that the Sgr A* data exhibit variability that exceeds what can be explained by the uncertainties in the data or by the effects of interstellar scattering. The magnitude of this variability can be a substantial fraction of the correlated flux density, reaching ~100% on some baselines. Through an exploration of simple geometric source models, we demonstrate that ring-like morphologies provide better fits to the Sgr A* data than do other morphologies with comparable complexity. We develop two strategies for fitting static geometric ring models to the time-variable Sgr A* data; one strategy fits models to short segments of data over which the source is static and averages these independent fits, while the other fits models to the full data set using a parametric model for the structural variability power spectrum around the average source structure. Both geometric modeling and image-domain feature extraction techniques determine the ring diameter to be 51.8 ± 2.3 μas (68% credible intervals), with the ring thickness constrained to have an FWHM between ~30% and 50% of the ring diameter. To bring the diameter measurements to a common physical scale, we calibrate them using synthetic data generated from GRMHD simulations. This calibration constrains the angular size of the gravitational radius to be ${4.8}_{-0.7}^{+1.4}$ μas, which we combine with an independent distance measurement from maser parallaxes to determine the mass of Sgr A* to be ${4.0}_{-0.6}^{+1.1}\times {10}^{6}$ M ⊙.
AU - BT - The Astrophysical Journal Letters IS - L15 LA - eng N2 -In this paper we quantify the temporal variability and image morphology of the horizon-scale emission from Sgr A*, as observed by the EHT in 2017 April at a wavelength of 1.3 mm. We find that the Sgr A* data exhibit variability that exceeds what can be explained by the uncertainties in the data or by the effects of interstellar scattering. The magnitude of this variability can be a substantial fraction of the correlated flux density, reaching ~100% on some baselines. Through an exploration of simple geometric source models, we demonstrate that ring-like morphologies provide better fits to the Sgr A* data than do other morphologies with comparable complexity. We develop two strategies for fitting static geometric ring models to the time-variable Sgr A* data; one strategy fits models to short segments of data over which the source is static and averages these independent fits, while the other fits models to the full data set using a parametric model for the structural variability power spectrum around the average source structure. Both geometric modeling and image-domain feature extraction techniques determine the ring diameter to be 51.8 ± 2.3 μas (68% credible intervals), with the ring thickness constrained to have an FWHM between ~30% and 50% of the ring diameter. To bring the diameter measurements to a common physical scale, we calibrate them using synthetic data generated from GRMHD simulations. This calibration constrains the angular size of the gravitational radius to be ${4.8}_{-0.7}^{+1.4}$ μas, which we combine with an independent distance measurement from maser parallaxes to determine the mass of Sgr A* to be ${4.0}_{-0.6}^{+1.1}\times {10}^{6}$ M ⊙.
PY - 2022 T1 - First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass T2 - The Astrophysical Journal Letters TI - First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass VL - 930 Y1 - 2022 ER - TY - JOUR A1 - The Event Horizon Telescope Collaboration AB -In this paper we provide a first physical interpretation for the Event Horizon Telescope's (EHT) 2017 observations of Sgr A*. Our main approach is to compare resolved EHT data at 230 GHz and unresolved non-EHT observations from radio to X-ray wavelengths to predictions from a library of models based on time-dependent general relativistic magnetohydrodynamics simulations, including aligned, tilted, and stellar-wind-fed simulations; radiative transfer is performed assuming both thermal and nonthermal electron distribution functions. We test the models against 11 constraints drawn from EHT 230 GHz data and observations at 86 GHz, 2.2 μm, and in the X-ray. All models fail at least one constraint. Light-curve variability provides a particularly severe constraint, failing nearly all strongly magnetized (magnetically arrested disk (MAD)) models and a large fraction of weakly magnetized models. A number of models fail only the variability constraints. We identify a promising cluster of these models, which are MAD and have inclination i ≤ 30°. They have accretion rate (5.2-9.5) × 10-9 M ⊙ yr-1, bolometric luminosity (6.8-9.2) × 1035 erg s-1, and outflow power (1.3-4.8) × 1038 erg s-1. We also find that all models with i ≥ 70° fail at least two constraints, as do all models with equal ion and electron temperature; exploratory, nonthermal model sets tend to have higher 2.2 μm flux density; and the population of cold electrons is limited by X-ray constraints due to the risk of bremsstrahlung overproduction. Finally, we discuss physical and numerical limitations of the models, highlighting the possible importance of kinetic effects and duration of the simulations.
AU - BT - The Astrophysical Journal Letters IS - L16 LA - eng N2 -In this paper we provide a first physical interpretation for the Event Horizon Telescope's (EHT) 2017 observations of Sgr A*. Our main approach is to compare resolved EHT data at 230 GHz and unresolved non-EHT observations from radio to X-ray wavelengths to predictions from a library of models based on time-dependent general relativistic magnetohydrodynamics simulations, including aligned, tilted, and stellar-wind-fed simulations; radiative transfer is performed assuming both thermal and nonthermal electron distribution functions. We test the models against 11 constraints drawn from EHT 230 GHz data and observations at 86 GHz, 2.2 μm, and in the X-ray. All models fail at least one constraint. Light-curve variability provides a particularly severe constraint, failing nearly all strongly magnetized (magnetically arrested disk (MAD)) models and a large fraction of weakly magnetized models. A number of models fail only the variability constraints. We identify a promising cluster of these models, which are MAD and have inclination i ≤ 30°. They have accretion rate (5.2-9.5) × 10-9 M ⊙ yr-1, bolometric luminosity (6.8-9.2) × 1035 erg s-1, and outflow power (1.3-4.8) × 1038 erg s-1. We also find that all models with i ≥ 70° fail at least two constraints, as do all models with equal ion and electron temperature; exploratory, nonthermal model sets tend to have higher 2.2 μm flux density; and the population of cold electrons is limited by X-ray constraints due to the risk of bremsstrahlung overproduction. Finally, we discuss physical and numerical limitations of the models, highlighting the possible importance of kinetic effects and duration of the simulations.
PY - 2022 T1 - First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole T2 - The Astrophysical Journal Letters TI - First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole VL - 930 Y1 - 2022 ER - TY - JOUR A1 - The Event Horizon Telescope Collaboration AB -Astrophysical black holes are expected to be described by the Kerr metric. This is the only stationary, vacuum, axisymmetric metric, without electromagnetic charge, that satisfies Einstein's equations and does not have pathologies outside of the event horizon. We present new constraints on potential deviations from the Kerr prediction based on 2017 EHT observations of Sagittarius A* (Sgr A*). We calibrate the relationship between the geometrically defined black hole shadow and the observed size of the ring-like images using a library that includes both Kerr and non-Kerr simulations. We use the exquisite prior constraints on the mass-to-distance ratio for Sgr A* to show that the observed image size is within ~10% of the Kerr predictions. We use these bounds to constrain metrics that are parametrically different from Kerr, as well as the charges of several known spacetimes. To consider alternatives to the presence of an event horizon, we explore the possibility that Sgr A* is a compact object with a surface that either absorbs and thermally reemits incident radiation or partially reflects it. Using the observed image size and the broadband spectrum of Sgr A*, we conclude that a thermal surface can be ruled out and a fully reflective one is unlikely. We compare our results to the broader landscape of gravitational tests. Together with the bounds found for stellar-mass black holes and the M87 black hole, our observations provide further support that the external spacetimes of all black holes are described by the Kerr metric, independent of their mass.
AU - BT - The Astrophysical Journal Letters IS - L17 LA - eng N2 -Astrophysical black holes are expected to be described by the Kerr metric. This is the only stationary, vacuum, axisymmetric metric, without electromagnetic charge, that satisfies Einstein's equations and does not have pathologies outside of the event horizon. We present new constraints on potential deviations from the Kerr prediction based on 2017 EHT observations of Sagittarius A* (Sgr A*). We calibrate the relationship between the geometrically defined black hole shadow and the observed size of the ring-like images using a library that includes both Kerr and non-Kerr simulations. We use the exquisite prior constraints on the mass-to-distance ratio for Sgr A* to show that the observed image size is within ~10% of the Kerr predictions. We use these bounds to constrain metrics that are parametrically different from Kerr, as well as the charges of several known spacetimes. To consider alternatives to the presence of an event horizon, we explore the possibility that Sgr A* is a compact object with a surface that either absorbs and thermally reemits incident radiation or partially reflects it. Using the observed image size and the broadband spectrum of Sgr A*, we conclude that a thermal surface can be ruled out and a fully reflective one is unlikely. We compare our results to the broader landscape of gravitational tests. Together with the bounds found for stellar-mass black holes and the M87 black hole, our observations provide further support that the external spacetimes of all black holes are described by the Kerr metric, independent of their mass.
PY - 2022 T1 - First Sagittarius A* Event Horizon Telescope Results. VI. Testing the Black Hole Metric T2 - The Astrophysical Journal Letters TI - First Sagittarius A* Event Horizon Telescope Results. VI. Testing the Black Hole Metric VL - 930 Y1 - 2022 ER - TY - JOUR A1 - Antonios Nathanail A1 - Prasun Dhang A1 - Christian M. Fromm AB - Observations of SgrA∗ have provided a lot of insight on low-luminosity accretion, with a handful of bright flares accompanied with orbital motion close to the horizon. It has been proposed that gas supply comes from stellar winds in the neighborhood of the supermassive black hole. We here argue that the flow at the vicinity of the black hole has a low magnetization and a structure of alternating polarity, totally dictated by the well-studied and long-ago proposed MRI turbulent process. This can be the case, provided that in larger distances from the black hole magnetic diffusivity is dominant, and thus, the magnetic field will never reach equipartition values. For SgrA∗, we show the immediate consequences of this specific magnetic field geometry, which are: (i) an intermittent flow that passes from quiescent states to flaring activity, (ii) no quasi-steady-state jet, (iii) no possibility of a magnetically arrested configuration. Moreover, a further distinctive feature of this geometry is the intense magnetic reconnection events, occurring as layers of opposite magnetic polarity, accreted in the vicinity of the black hole. Finally, we argue that the absence of a jet structure in such case will be a smoking gun in 43 and 86 GHz observations. AU - BT - Monthly Notices of the Royal Astronomical Society IS - 4 LA - eng N2 - Observations of SgrA∗ have provided a lot of insight on low-luminosity accretion, with a handful of bright flares accompanied with orbital motion close to the horizon. It has been proposed that gas supply comes from stellar winds in the neighborhood of the supermassive black hole. We here argue that the flow at the vicinity of the black hole has a low magnetization and a structure of alternating polarity, totally dictated by the well-studied and long-ago proposed MRI turbulent process. This can be the case, provided that in larger distances from the black hole magnetic diffusivity is dominant, and thus, the magnetic field will never reach equipartition values. For SgrA∗, we show the immediate consequences of this specific magnetic field geometry, which are: (i) an intermittent flow that passes from quiescent states to flaring activity, (ii) no quasi-steady-state jet, (iii) no possibility of a magnetically arrested configuration. Moreover, a further distinctive feature of this geometry is the intense magnetic reconnection events, occurring as layers of opposite magnetic polarity, accreted in the vicinity of the black hole. Finally, we argue that the absence of a jet structure in such case will be a smoking gun in 43 and 86 GHz observations. PY - 2022 SP - 5204 EP - 5210 T1 - Magnetic field structure in the vicinity of a supermassive black hole in low-luminosity galaxies: the case of Sgr A* T2 - Monthly Notices of the Royal Astronomical Society TI - Magnetic field structure in the vicinity of a supermassive black hole in low-luminosity galaxies: the case of Sgr A* UR - https://doi.org/10.1093/mnras/stac1276 VL - 513 Y1 - 2022 ER - TY - JOUR A1 - Christian M. Fromm A1 - Alejandro Cruz-Osorio A1 - Yosuke Mizuno A1 - Antonios Nathanail A1 - Ziri Younsi A1 - Oliver Porth A1 - Hector Olivares A1 - Jordy Davelaar A1 - Heino Falcke A1 - Michael Kramer A1 - Luciano Rezzolla AB - Context. The recent 230 GHz observations of the Event Horizon Telescope are able to image the innermost structure of M 87 and show a ring-like structure that agrees with thermal synchrotron emission generated in a torus surrounding a supermassive black hole. However, at lower frequencies, M 87 is characterised by a large-scale and edge-brightened jet with clear signatures of non-thermal emission. In order to bridge the gap between these scales and to provide a theoretical interpretation of these observations, we perform general relativistic magnetohydrodynamic simulations of accretion onto black holes and jet launching.The direct detection of a bright, ring-like structure in horizon-resolving images of M87* by the Event Horizon Telescope (EHT) is a striking validation of general relativity. The angular size and shape of the ring is a degenerate measure of the location of the emission region, mass, and spin of the black hole. However, we show that the observation of multiple rings, corresponding to the low-order photon rings, can break this degeneracy and produce mass and spin measurements independent of the shape of the rings. We describe two potential experiments that would measure the spin. In the first, observations of the direct emission and n = 1 photon ring are made at multiple epochs with different emission locations. This method is conceptually similar to spacetime constraints that arise from variable structures (or hot spots) in that it breaks the near-perfect degeneracy between emission location, mass, and spin for polar observers using temporal variability. In the second, observations of the direct emission and n = 1 and n = 2 photon rings are made during a single epoch. For both schemes, additional observations comprise a test of general relativity. Thus, comparisons of EHT observations in 2017 and 2018 may be capable of producing the first horizon-scale spin estimates of M87* inferred from strong lensing alone. Additional observation campaigns from future high-frequency, Earth-sized, and space-based radio interferometers can produce high-precision tests of general relativity.
AU - BT - The Astrophysical Journal IS - 6 LA - eng N2 -The direct detection of a bright, ring-like structure in horizon-resolving images of M87* by the Event Horizon Telescope (EHT) is a striking validation of general relativity. The angular size and shape of the ring is a degenerate measure of the location of the emission region, mass, and spin of the black hole. However, we show that the observation of multiple rings, corresponding to the low-order photon rings, can break this degeneracy and produce mass and spin measurements independent of the shape of the rings. We describe two potential experiments that would measure the spin. In the first, observations of the direct emission and n = 1 photon ring are made at multiple epochs with different emission locations. This method is conceptually similar to spacetime constraints that arise from variable structures (or hot spots) in that it breaks the near-perfect degeneracy between emission location, mass, and spin for polar observers using temporal variability. In the second, observations of the direct emission and n = 1 and n = 2 photon rings are made during a single epoch. For both schemes, additional observations comprise a test of general relativity. Thus, comparisons of EHT observations in 2017 and 2018 may be capable of producing the first horizon-scale spin estimates of M87* inferred from strong lensing alone. Additional observation campaigns from future high-frequency, Earth-sized, and space-based radio interferometers can produce high-precision tests of general relativity.
PY - 2022 SP - 1 EP - 12 T1 - Measuring Spin from Relative Photon-ring Sizes T2 - The Astrophysical Journal TI - Measuring Spin from Relative Photon-ring Sizes UR - https://doi.org/10.3847/1538-4357/ac4970 VL - 927 Y1 - 2022 ER - TY - JOUR A1 - Prashant Kocherlakota A1 - Luciano Rezzolla A1 - Event Horizon Telescope Collaboration AU - BT - Physical Review D IS - 10 LA - eng PY - 2021 SP - 40 EP - 47 T1 - Constraints on non-Einsteinian black-hole charges with the 2019 EHT observations of M87 T2 - Physical Review D TI - Constraints on non-Einsteinian black-hole charges with the 2019 EHT observations of M87 UR - https://journals.aps.org/prd/abstract/10.1103/PhysRevD.103.104047 VL - 103 Y1 - 2021 ER - TY - JOUR A1 - et EHT Collaboration al. AU - BT - ApJL IS - L12 LA - eng PY - 2021 EP - 48 T1 - First M87 Event Horizon Telescope Results. VII. Polarization of the Ring T2 - ApJL TI - First M87 Event Horizon Telescope Results. VII. Polarization of the Ring UR - https://iopscience.iop.org/article/10.3847/2041-8213/abe71d VL - 910 Y1 - 2021 ER - TY - JOUR A1 - et EHT Collaboration al. AU - BT - ApJL IS - L13 LA - eng PY - 2021 EP - 43 T1 - First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon T2 - ApJL TI - First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon UR - https://iopscience.iop.org/article/10.3847/2041-8213/abe4de VL - 910 Y1 - 2021 ER - TY - JOUR A1 - et C. Goddi al. AU - BT - ApJL IS - L14 LA - eng PY - 2021 EP - 54 T1 - Polarimetric Properties of Event Horizon Telescope Targets from ALMA T2 - ApJL TI - Polarimetric Properties of Event Horizon Telescope Targets from ALMA UR - https://iopscience.iop.org/article/10.3847/2041-8213/abee6a VL - 910 Y1 - 2021 ER - TY - JOUR A1 - et J. C. Algaba al. AB - In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109M⊙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded. AU - BT - ApJL LA - eng N2 - In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109M⊙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded. PY - 2021 EP - L11 T1 - Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign T2 - ApJL TI - Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign UR - https://iopscience.iop.org/article/10.3847/2041-8213/abef71 VL - 911 Y1 - 2021 ER - TY - JOUR A1 - Michael Janssen A1 - Heino Falcke A1 - Matthias Kadler A1 - Eduardo Ros A1 - the EHT Collaboration AB - Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources. Centaurus A is the closest radio-loud source to Earth. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses. AU - BT - Nature Astronomy LA - eng N2 - Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources. Centaurus A is the closest radio-loud source to Earth. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses. PY - 2021 SP - 1017 EP - 1028 T1 - Event Horizon Telescope observations of the jet launching and collimation in Centaurus A T2 - Nature Astronomy TI - Event Horizon Telescope observations of the jet launching and collimation in Centaurus A UR - https://doi.org/10.1038/s41550-021-01417-w VL - 5 Y1 - 2021 ER - TY - JOUR A1 - Razieh Emami A1 - Richard Anantua A1 - Andrew A. Chael A1 - Abraham Loeb AB - We study the effects of including a nonzero positron-to-electron fraction in emitting plasma on the polarized spectral energy distributions and submillimeter images of jet and accretion flow models for near-horizon emission from M87* and Sgr A*. For M87*, we consider a semi-analytic fit to the force-free plasma regions of a general relativistic magnetohydrodynamic jet simulation, which we populate with power-law leptons with a constant electron-to-magnetic pressure ratio. For Sgr A*, we consider a standard self-similar radiatively inefficient accretion flow where the emission is predominantly from thermal leptons with a small fraction in a power-law tail. In both models, we fix the positron-to-electron ratio throughout the emission region. We generate polarized images and spectra from our models using the general relativistic ray tracing and radiative transfer from GRTRANS. We find that a substantial positron fraction reduces the circular polarization fraction at IR and higher frequencies. However, in submillimeter images, higher positron fractions increase polarization fractions due to strong effects of Faraday conversion. We find an M87* jet model that best matches the available broadband total intensity, and 230 GHz polarization data is a sub-equipartition, with positron fraction of ≃10%. We show that jet models with significant positron fractions do not satisfy the polarimetric constraints at 230 GHz from the Event Horizon Telescope (EHT). Sgr A* models show similar trends in their polarization fractions with increasing pair fraction. Both models suggest that resolved, polarized EHT images are useful to constrain the presence of pairs at 230 GHz emitting regions of M87* and Sgr A*. AU - BT - The Astrophysical Journal LA - eng N2 - We study the effects of including a nonzero positron-to-electron fraction in emitting plasma on the polarized spectral energy distributions and submillimeter images of jet and accretion flow models for near-horizon emission from M87* and Sgr A*. For M87*, we consider a semi-analytic fit to the force-free plasma regions of a general relativistic magnetohydrodynamic jet simulation, which we populate with power-law leptons with a constant electron-to-magnetic pressure ratio. For Sgr A*, we consider a standard self-similar radiatively inefficient accretion flow where the emission is predominantly from thermal leptons with a small fraction in a power-law tail. In both models, we fix the positron-to-electron ratio throughout the emission region. We generate polarized images and spectra from our models using the general relativistic ray tracing and radiative transfer from GRTRANS. We find that a substantial positron fraction reduces the circular polarization fraction at IR and higher frequencies. However, in submillimeter images, higher positron fractions increase polarization fractions due to strong effects of Faraday conversion. We find an M87* jet model that best matches the available broadband total intensity, and 230 GHz polarization data is a sub-equipartition, with positron fraction of ≃10%. We show that jet models with significant positron fractions do not satisfy the polarimetric constraints at 230 GHz from the Event Horizon Telescope (EHT). Sgr A* models show similar trends in their polarization fractions with increasing pair fraction. Both models suggest that resolved, polarized EHT images are useful to constrain the presence of pairs at 230 GHz emitting regions of M87* and Sgr A*. PY - 2021 EP - 272 SP - 1 EP - 27 T1 - Positron Effects on Polarized Images and Spectra from Jet and Accretion Flow Models of M87* and Sgr A* T2 - The Astrophysical Journal TI - Positron Effects on Polarized Images and Spectra from Jet and Accretion Flow Models of M87* and Sgr A* UR - https://doi.org/10.3847/1538-4357/ac2950 VL - 923 Y1 - 2021 ER - TY - JOUR A1 - Maciek Wielgus AB -Under very general assumptions on the accretion flow geometry, images of a black hole illuminated by electromagnetic radiation display a sequence of photon rings (demagnified and rotated copies of the direct image) which asymptotically approach a purely theoretical critical curve—the outline of the black hole photon shell. To a distant observer, these images appear dominated by the direct emission, which forms a ring whose diameter is primarily determined by the effective radius of the emitting region. For that reason, connecting the image diameter seen by a distant observer to the properties of the underlying spacetime crucially relies on a calibration that necessarily depends on the assumed astrophysical source model. On the other hand, the diameter of the photon rings depends more on the detailed geometry of the spacetime than on the source structure. As such, a photon ring detection would allow for the spacetime metric to be probed in a less model-dependent way, enabling more robust tests of general relativity and the Kerr hypothesis. Here we present the photon ring structure of several spherically symmetric black hole spacetimes and perform comparisons with the Schwarzschild/Kerr case. We offer our perspective on future tests of the spacetime metric with photon rings, discussing the challenges and opportunities involved.
Under very general assumptions on the accretion flow geometry, images of a black hole illuminated by electromagnetic radiation display a sequence of photon rings (demagnified and rotated copies of the direct image) which asymptotically approach a purely theoretical critical curve—the outline of the black hole photon shell. To a distant observer, these images appear dominated by the direct emission, which forms a ring whose diameter is primarily determined by the effective radius of the emitting region. For that reason, connecting the image diameter seen by a distant observer to the properties of the underlying spacetime crucially relies on a calibration that necessarily depends on the assumed astrophysical source model. On the other hand, the diameter of the photon rings depends more on the detailed geometry of the spacetime than on the source structure. As such, a photon ring detection would allow for the spacetime metric to be probed in a less model-dependent way, enabling more robust tests of general relativity and the Kerr hypothesis. Here we present the photon ring structure of several spherically symmetric black hole spacetimes and perform comparisons with the Schwarzschild/Kerr case. We offer our perspective on future tests of the spacetime metric with photon rings, discussing the challenges and opportunities involved.
3C 279 is an archetypal blazar with a prominent radio jet that show broadband flux density variability across the entire electromagnetic spectrum. We use an ultra-high angular resolution technique - global Very Long Baseline Interferometry (VLBI) at 1.3 mm (230 GHz) - to resolve the innermost jet of 3C 279 in order to study its fine-scale morphology close to the jet base where highly variable γ-ray emission is thought to originate, according to various models. The source was observed during four days in April 2017 with the Event Horizon Telescope at 230 GHz, including the phased Atacama Large Millimeter/submillimeter Array (ALMA), at an angular resolution of ∼20 μas (at a redshift of z = 0.536 this corresponds to ∼0.13 pc ∼ 1700 Schwarzschild radii with a black hole mass MBH = 8 × 108 M☉). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation. We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across different imaging methods and model-fitting techniques, and therefore appears robust. Owing to its compactness and brightness, we associate the northern nuclear structure as the VLBI "core". This morphology can be interpreted as either a broad resolved jet base or a spatially bent jet. We also find significant day-to-day variations in the closure phases, which appear most pronounced on the triangles with the longest baselines. Our analysis shows that this variation is related to a systematic change of the source structure. Two inner jet components move non-radially at apparent speeds of ∼15 c and ∼20 c (∼1.3 and ∼1.7 μas day-1, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3 mm core and the outer jet. The intrinsic brightness temperature of the jet components are ≲1010 K, a magnitude or more lower than typical values seen at ≥7 mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C 279 becomes optically thin at short (mm) wavelengths.
The data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/640/A69 and at http://https://eventhorizontelescope.org/for-astronomers/data AU - BT - Astronomy and Astrophysics IS - A69 LA - eng N2 -
3C 279 is an archetypal blazar with a prominent radio jet that show broadband flux density variability across the entire electromagnetic spectrum. We use an ultra-high angular resolution technique - global Very Long Baseline Interferometry (VLBI) at 1.3 mm (230 GHz) - to resolve the innermost jet of 3C 279 in order to study its fine-scale morphology close to the jet base where highly variable γ-ray emission is thought to originate, according to various models. The source was observed during four days in April 2017 with the Event Horizon Telescope at 230 GHz, including the phased Atacama Large Millimeter/submillimeter Array (ALMA), at an angular resolution of ∼20 μas (at a redshift of z = 0.536 this corresponds to ∼0.13 pc ∼ 1700 Schwarzschild radii with a black hole mass MBH = 8 × 108 M☉). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation. We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across different imaging methods and model-fitting techniques, and therefore appears robust. Owing to its compactness and brightness, we associate the northern nuclear structure as the VLBI "core". This morphology can be interpreted as either a broad resolved jet base or a spatially bent jet. We also find significant day-to-day variations in the closure phases, which appear most pronounced on the triangles with the longest baselines. Our analysis shows that this variation is related to a systematic change of the source structure. Two inner jet components move non-radially at apparent speeds of ∼15 c and ∼20 c (∼1.3 and ∼1.7 μas day-1, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3 mm core and the outer jet. The intrinsic brightness temperature of the jet components are ≲1010 K, a magnitude or more lower than typical values seen at ≥7 mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C 279 becomes optically thin at short (mm) wavelengths.
The data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/640/A69 and at http://https://eventhorizontelescope.org/for-astronomers/data PY - 2020 EP - 21 T1 - Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution T2 - Astronomy and Astrophysics TI - Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution UR - https://www.aanda.org/articles/aa/abs/2020/08/aa37493-20/aa37493-20.html VL - 640 Y1 - 2020 ER - TY - JOUR A1 - et R. Gold al. AU - BT - The Astrophysical Journal IS - 2 LA - eng PY - 2020 EP - id. 148 T1 - Verification of Radiative Transfer Schemes for the EHT T2 - The Astrophysical Journal TI - Verification of Radiative Transfer Schemes for the EHT UR - https://iopscience.iop.org/article/10.3847/1538-4357/ab96c6 VL - 897 Y1 - 2020 ER - TY - JOUR A1 - et A. Broderick al. AU - BT - The Astrophysical Journal IS - 2 LA - eng PY - 2020 EP - id. 139 T1 - THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope T2 - The Astrophysical Journal TI - THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope UR - https://iopscience.iop.org/article/10.3847/1538-4357/ab91a4 VL - 897 Y1 - 2020 ER - TY - JOUR A1 - et F. Roelofs al. AU - BT - Astronomy & Astrophysics IS - A5 LA - eng PY - 2020 EP - 19 T1 - SYMBA: An end-to-end VLBI synthetic data generation pipeline. Simulating Event Horizon Telescope observations of M 87 T2 - Astronomy & Astrophysics TI - SYMBA: An end-to-end VLBI synthetic data generation pipeline. Simulating Event Horizon Telescope observations of M 87 UR - https://www.aanda.org/articles/aa/full_html/2020/04/aa36622-19/aa36622-19.html VL - 636 Y1 - 2020 ER - TY - JOUR A1 - et T. Bronzwaer al. AU - BT - Astronomy & Astrophysics IS - A126 LA - eng PY - 2020 EP - 13 T1 - RAPTOR. II. Polarized radiative transfer in curved spacetime T2 - Astronomy & Astrophysics TI - RAPTOR. II. Polarized radiative transfer in curved spacetime UR - https://ui.adsabs.harvard.edu/abs/2020A%26A...641A.126B/abstract VL - 641 Y1 - 2020 ER - TY - JOUR A1 - et M. Wielgus al. AU - BT - Astrophysical Journal IS - 1 LA - eng PY - 2020 EP - 28 T1 - Monitoring the Morphology of M87* in 2009-2017 with the Event Horizon Telescope T2 - Astrophysical Journal TI - Monitoring the Morphology of M87* in 2009-2017 with the Event Horizon Telescope UR - https://ui.adsabs.harvard.edu/abs/2020ApJ...901...67W/abstract VL - 901 Y1 - 2020 ER - TY - JOUR A1 - et M. Johnson al. AU - BT - Science Advances IS - 12 LA - eng PY - 2020 EP - eaaz1310 T1 - Universal interferometric signatures of a black hole's photon ring T2 - Science Advances TI - Universal interferometric signatures of a black hole's photon ring UR - https://ui.adsabs.harvard.edu/abs/2020SciA....6.1310J/abstract VL - 6 Y1 - 2020 ER - TY - JOUR A1 - et E. Kravchenko al. AU - BT - Astronomy & Astrophysics IS - L6 LA - eng PY - 2020 EP - 9 T1 - Linear polarization in the nucleus of M87 at 7 mm and 1.3 cm T2 - Astronomy & Astrophysics TI - Linear polarization in the nucleus of M87 at 7 mm and 1.3 cm UR - https://ui.adsabs.harvard.edu/abs/2020A%26A...637L...6K/abstract VL - 637 Y1 - 2020 ER - TY - JOUR A1 - et D. Psaltis al. AU - BT - Physical Review Letters IS - 14 LA - eng PY - 2020 EP - 141104 T1 - Gravitational Test beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole T2 - Physical Review Letters TI - Gravitational Test beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole UR - https://ui.adsabs.harvard.edu/abs/2020PhRvL.125n1104P/abstract VL - 125 Y1 - 2020 ER - TY - JOUR A1 - et J. Dexter al. AU - BT - Monthly Notices of the Royal Astroonomical Society IS - 3 LA - eng PY - 2020 SP - 4168 EP - 4186 T1 - A parameter survey of Sgr A* radiative models from GRMHD simulations with self-consistent electron heating T2 - Monthly Notices of the Royal Astroonomical Society TI - A parameter survey of Sgr A* radiative models from GRMHD simulations with self-consistent electron heating UR - https://academic.oup.com/mnras/article-abstract/494/3/4168/5817372?redirectedFrom=fulltext VL - 494 Y1 - 2020 ER - TY - JOUR A1 - et The EHT Collaboration al. AU - BT - ApJL LA - eng PY - 2019 EP - 1 T1 - First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole T2 - ApJL TI - First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole UR - https://iopscience.iop.org/article/10.3847/2041-8213/ab0ec7 VL - 875 Y1 - 2019 ER - TY - JOUR A1 - et The EHT Collaboration al. AU - BT - ApJL LA - eng PY - 2019 EP - 2 T1 - First M87 Event Horizon Telescope Results. II. Array and Instrumentation T2 - ApJL TI - First M87 Event Horizon Telescope Results. II. Array and Instrumentation UR - https://iopscience.iop.org/article/10.3847/2041-8213/ab0c96 VL - 875 Y1 - 2019 ER - TY - JOUR A1 - et The EHT Collaboration al. AU - BT - ApJL LA - eng PY - 2019 EP - 3 T1 - First M87 Event Horizon Telescope Results. III. Data Processing and Calibration T2 - ApJL TI - First M87 Event Horizon Telescope Results. III. Data Processing and Calibration UR - https://iopscience.iop.org/article/10.3847/2041-8213/ab0c57 VL - 875 Y1 - 2019 ER - TY - JOUR A1 - et The EHT Collaboration al. AU - BT - ApJL LA - eng PY - 2019 EP - 4 T1 - First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole T2 - ApJL TI - First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole UR - https://iopscience.iop.org/article/10.3847/2041-8213/ab0e85 VL - 875 Y1 - 2019 ER - TY - JOUR A1 - et The EHT Collaboration al. AU - BT - ApJL LA - eng PY - 2019 EP - 5 T1 - First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring T2 - ApJL TI - First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring UR - https://iopscience.iop.org/article/10.3847/2041-8213/ab0f43 VL - 875 Y1 - 2019 ER - TY - JOUR A1 - et The EHT Collaboration al. AU - BT - ApJL LA - eng PY - 2019 EP - 6 T1 - First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole T2 - ApJL TI - First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole UR - https://iopscience.iop.org/article/10.3847/2041-8213/ab1141 VL - 875 Y1 - 2019 ER - TY - JOUR A1 - et F. Roelofs al. AU - BT - A&A IS - 124 LA - eng PY - 2019 T1 - Simulations of imaging the event horizon of Sagittarius A* from space T2 - A&A TI - Simulations of imaging the event horizon of Sagittarius A* from space UR - https://www.aanda.org/articles/aa/abs/2019/05/aa32423-17/aa32423-17.html VL - 625 Y1 - 2019 ER - TY - JOUR A1 - et S. Issaoun al. AU - BT - ApJ IS - 1 LA - eng PY - 2019 EP - 30 T1 - The Size, Shape, and Scattering of Sagittarius A* at 86 GHz: First VLBI with ALMA T2 - ApJ TI - The Size, Shape, and Scattering of Sagittarius A* at 86 GHz: First VLBI with ALMA UR - https://iopscience.iop.org/article/10.3847/1538-4357/aaf732 VL - 871 Y1 - 2019 ER - TY - JOUR A1 - et Z. Zhu al. AU - BT - ApJ IS - 1 LA - eng PY - 2019 EP - 6 T1 - Testing General Relativity with the Black Hole Shadow Size and Asymmetry of Sagittarius A*: Limitations from Interstellar Scattering T2 - ApJ TI - Testing General Relativity with the Black Hole Shadow Size and Asymmetry of Sagittarius A*: Limitations from Interstellar Scattering UR - https://iopscience.iop.org/article/10.3847/1538-4357/aaef3d VL - 870 Y1 - 2019 ER - TY - JOUR A1 - et L. Blackburn al. AU - BT - ApJ IS - 23 LA - eng PY - 2019 T1 - EHT-HOPS pipeline for millimeter VLBI data reduction T2 - ApJ TI - EHT-HOPS pipeline for millimeter VLBI data reduction UR - https://iopscience.iop.org/article/10.3847/1538-4357/ab328d VL - 882 Y1 - 2019 ER - TY - JOUR A1 - et M. Janssen al. AU - BT - A&A IS - 75 LA - eng PY - 2019 T1 - rPICARD: A CASA-based Calibration Pipeline for VLBI Data. Calibration and imaging of 7 mm VLBA observations of the AGN jet in M87 T2 - A&A TI - rPICARD: A CASA-based Calibration Pipeline for VLBI Data. Calibration and imaging of 7 mm VLBA observations of the AGN jet in M87 UR - https://www.aanda.org/articles/aa/abs/2019/06/aa35181-19/aa35181-19.html VL - 626 Y1 - 2019 ER - TY - JOUR A1 - et C. Goddi al. AU - BT - PASP IS - 1001 LA - eng PY - 2019 EP - 075003 T1 - Calibration of ALMA as a phased array: ALMA observations during the 2017 VLBI campaign T2 - PASP TI - Calibration of ALMA as a phased array: ALMA observations during the 2017 VLBI campaign UR - https://iopscience.iop.org/article/10.1088/1538-3873/ab136a VL - 131 Y1 - 2019 ER - TY - JOUR A1 - et O. Porth al. AU - BT - ApJS IS - 26 LA - eng PY - 2019 T1 - The Event Horizon General Relativistic Magnetohydrodynamic Code Comparison Project T2 - ApJS TI - The Event Horizon General Relativistic Magnetohydrodynamic Code Comparison Project UR - https://iopscience.iop.org/article/10.3847/1538-4365/ab29fd VL - 243 Y1 - 2019 ER - TY - JOUR A1 - et L. Christensen al. AU - BT - CAPJ IS - 11 LA - eng PY - 2019 T1 - An Unprecedented Global Communications Campaign for the Event Horizon Telescope First Black Hole Image T2 - CAPJ TI - An Unprecedented Global Communications Campaign for the Event Horizon Telescope First Black Hole Image UR - https://www.capjournal.org/issues/26/26_11.pdf VL - 26 Y1 - 2019 ER - TY - JOUR A1 - et C. Goddi al. AU - LA - eng PY - 2019 SP - 25 EP - 35 T1 - First M87 Event Horizon Telescope Results and the Role of ALMA TI - First M87 Event Horizon Telescope Results and the Role of ALMA UR - https://www.eso.org/sci/publications/messenger/archive/no.177-sep19/messenger-no177-25-35.pdf VL - 177 Y1 - 2019 ER - TY - JOUR A1 - Y. Mizuno A1 - Z. Younsi A1 - C. M. Fromm A1 - O. Porth A1 - M. De Laurentis A1 - H. Olivares A1 - H. Falcke A1 - M. Kramer A1 - L. Rezzolla AU - BT - Nat. Astro. (Letter) LA - eng PY - 2018 T1 - The current ability to test theories of gravity with black hole shadows T2 - Nat. Astro. (Letter) TI - The current ability to test theories of gravity with black hole shadows Y1 - 2018 ER - TY - JOUR A1 - et L. Medeiros al. AU - BT - ApJ IS - 1 LA - eng PY - 2018 EP - 7 T1 - Principal Component Analysis as a Tool for Characterizing Black Hole Images and Variability T2 - ApJ TI - Principal Component Analysis as a Tool for Characterizing Black Hole Images and Variability UR - https://iopscience.iop.org/article/10.3847/1538-4357/aad37a VL - 864 Y1 - 2018 ER - TY - JOUR A1 - et A. Chael al. AU - BT - MNRAS IS - 4 LA - eng PY - 2018 SP - 5209 EP - 5229 T1 - The role of electron heating physics in images and variability of the Galactic Center black hole Sagittarius A* T2 - MNRAS TI - The role of electron heating physics in images and variability of the Galactic Center black hole Sagittarius A* UR - https://academic.oup.com/mnras/article-abstract/478/4/5209/4996793 VL - 478 Y1 - 2018 ER - TY - JOUR A1 - J. Davelaar A1 - M. Mościbrodzka A1 - T. Bronzwaer A1 - H. Falcke AU - BT - A&A IS - A34 LA - eng PY - 2018 T1 - General relativistic magnetohydrodynamical κ-jet models for Sagittarius A* T2 - A&A TI - General relativistic magnetohydrodynamical κ-jet models for Sagittarius A* VL - 612 Y1 - 2018 ER - TY - JOUR A1 - A. A. Chael A1 - M. D. Johnson A1 - K. L. Bouman A1 - L. L. Blackburn A1 - K. Akiyama A1 - R. Narayan AU - BT - ApJ IS - 1 LA - eng PY - 2018 EP - 23 T1 - Interferometric Imaging Directly with Closure Phases and Closure Amplitudes T2 - ApJ TI - Interferometric Imaging Directly with Closure Phases and Closure Amplitudes VL - 857 Y1 - 2018 ER - TY - JOUR A1 - M. Mościbrodzka A1 - C. F. Gammie AU - BT - MNRAS IS - 1 LA - eng PY - 2018 EP - 43 T1 - IPOLE - semi-analytic scheme for relativistic polarized radiative transport T2 - MNRAS TI - IPOLE - semi-analytic scheme for relativistic polarized radiative transport VL - 457 Y1 - 2018 ER - TY - JOUR A1 - S. B. Giddings A1 - D. Psaltis AU - BT - Phys. Rev. D IS - 084035 LA - eng PY - 2018 T1 - Event Horizon Telescope Observations as Probes for Quantum Structure of Astrophysical Black Holes T2 - Phys. Rev. D TI - Event Horizon Telescope Observations as Probes for Quantum Structure of Astrophysical Black Holes VL - 97 Y1 - 2018 ER - TY - JOUR A1 - L. D. Matthews A1 - G. B. Crew A1 - S. S. Doeleman A1 - R. Lacasse A1 - A. F. Saez A1 - ALMA Phasing Project Team AU - BT - PASP IS - 983 LA - eng PY - 2018 EP - 015002 T1 - The ALMA Phasing System: A Beamforming Capability for Ultra-high-resolution Science at (Sub)Millimeter Wavelengths T2 - PASP TI - The ALMA Phasing System: A Beamforming Capability for Ultra-high-resolution Science at (Sub)Millimeter Wavelengths VL - 130 Y1 - 2018 ER - TY - JOUR A1 - et J. Kim al. AU - BT - ApJ IS - 2 LA - eng PY - 2018 EP - 129 T1 - The 1.4 mm core of Cen A: first VLBI results with the South Pole Telescope T2 - ApJ TI - The 1.4 mm core of Cen A: first VLBI results with the South Pole Telescope UR - https://iopscience.iop.org/article/10.3847/1538-4357/aac7c6 VL - 861 Y1 - 2018 ER - TY - JOUR A1 - et R. Lu al. AU - BT - ApJ IS - 1 LA - eng PY - 2018 EP - 60 T1 - Detection of intrinsic source structure at ~3 Schwarzschild radii with Millimeter-VLBI observations of Sgr A* T2 - ApJ TI - Detection of intrinsic source structure at ~3 Schwarzschild radii with Millimeter-VLBI observations of Sgr A* VL - 859 Y1 - 2018 ER - TY - JOUR A1 - et K. Kuromochi al. AU - BT - ApJ IS - 1 LA - eng PY - 2018 EP - 56 T1 - Superresolution Interferometric Imaging with Sparse Modeling Using Total Squared Variation -- Application to Imaging the Black Hole Shadow T2 - ApJ TI - Superresolution Interferometric Imaging with Sparse Modeling Using Total Squared Variation -- Application to Imaging the Black Hole Shadow UR - https://iopscience.iop.org/article/10.3847/1538-4357/aab6b5 VL - 2018 Y1 - 2018 ER - TY - JOUR A1 - L. Medeiros A1 - C.-K. Chan A1 - F. Özel A1 - D. Psaltis A1 - J. Kim A1 - D. P. Marrone A1 - A. Sadowski AU - BT - ApJ IS - 2 LA - eng PY - 2018 EP - 13 T1 - GRMHD Simulations of Visibility Amplitude Variability for Event Horizon Telescope Images of Sgr A* T2 - ApJ TI - GRMHD Simulations of Visibility Amplitude Variability for Event Horizon Telescope Images of Sgr A* VL - 856 Y1 - 2018 ER - TY - JOUR A1 - et C.-K. Chan al. AU - BT - ApJ IS - 1 LA - eng PY - 2018 EP - 59 T1 - GRay2: A General Purpose Geodesic Integrator for Kerr Spacetimes T2 - ApJ TI - GRay2: A General Purpose Geodesic Integrator for Kerr Spacetimes VL - 867 Y1 - 2018 ER - TY - JOUR A1 - D. Ball A1 - F. Özel A1 - D. Psaltis A1 - C.-K. Chan A1 - L. Sironi AU - BT - ApJ IS - 2 LA - eng PY - 2018 EP - 184 T1 - The Properties of Reconnection Current Sheets in GRMHD Simulations of Radiatively Inefficient Accretion Flows T2 - ApJ TI - The Properties of Reconnection Current Sheets in GRMHD Simulations of Radiatively Inefficient Accretion Flows VL - 853 Y1 - 2018 ER - TY - CONF A1 - et J. Kim al. AU - BT - SPIE LA - eng PY - 2018 T1 - A VLBI receiving system for the South Pole Telescope T2 - SPIE TI - A VLBI receiving system for the South Pole Telescope UR - https://doi.org/10.1117/12.2301005 VL - 10708 Y1 - 2018 ER - TY - JOUR A1 - et J.-Y. Kim al. AU - BT - A&A IS - A LA - eng PY - 2018 EP - 188 T1 - The limb-brightened jet of M87 down to the 7 Schwarzschild radii scale T2 - A&A TI - The limb-brightened jet of M87 down to the 7 Schwarzschild radii scale UR - https://www.aanda.org/articles/aa/abs/2018/08/aa32921-18/aa32921-18.html VL - 616 Y1 - 2018 ER - TY - JOUR A1 - A. Jiménez-Rosales A1 - J. Dexter AU - BT - MNRAS IS - 2 LA - eng PY - 2018 SP - 1875 EP - 1883 T1 - The impact of Faraday effects on polarized black hole images of Sagittarius A* T2 - MNRAS TI - The impact of Faraday effects on polarized black hole images of Sagittarius A* UR - https://academic.oup.com/mnras/article/478/2/1875/4995232 VL - 478 Y1 - 2018 ER - TY - JOUR A1 - et G. C. Bower al. AU - BT - ApJ IS - 2 LA - eng PY - 2018 EP - 101 T1 - ALMA Polarimetry of Sgr A*: Probing the Accretion Flow from the Event Horizon to the Bondi Radius T2 - ApJ TI - ALMA Polarimetry of Sgr A*: Probing the Accretion Flow from the Event Horizon to the Bondi Radius UR - https://iopscience.iop.org/article/10.3847/1538-4357/aae983 VL - 868 Y1 - 2018 ER - TY - JOUR A1 - et M. D. Johnson al. AU - BT - ApJ IS - 2 LA - eng PY - 2018 EP - 104 T1 - The Scattering and Intrinsic Structure of Sagittarius A* at Radio Wavelengths T2 - ApJ TI - The Scattering and Intrinsic Structure of Sagittarius A* at Radio Wavelengths UR - https://iopscience.iop.org/article/10.3847/1538-4357/aadcff VL - 865 Y1 - 2018 ER - TY - JOUR A1 - et A. Chael al. AU - BT - MNRAS IS - 2 LA - eng PY - 2018 SP - 2873 EP - 2895 T1 - Two-temperature, Magnetically Arrested Disc simulations of the jet from the supermassive black hole in M87 T2 - MNRAS TI - Two-temperature, Magnetically Arrested Disc simulations of the jet from the supermassive black hole in M87 UR - https://academic.oup.com/mnras/article/486/2/2873/5432368 VL - 486 Y1 - 2018 ER - TY - JOUR A1 - H.-Y. Pu A1 - A. Broderick AU - BT - ApJ IS - 2 LA - eng PY - 2018 EP - 148 T1 - Probing the Innermost Accretion Flow Geometry of Sgr A* with Event Horizon Telescope T2 - ApJ TI - Probing the Innermost Accretion Flow Geometry of Sgr A* with Event Horizon Telescope UR - https://iopscience.iop.org/article/10.3847/1538-4357/aad086 VL - 863 Y1 - 2018 ER - TY - ICOMM A1 - A. Lobanov AU - BT - Nat. Astro. (Comment) DO - 10.1038/s41550-017-0069 LA - eng PY - 2017 EP - 0069 T1 - Beyond the event horizon or altogether without it? T2 - Nat. Astro. (Comment) TI - Beyond the event horizon or altogether without it? VL - 1 Y1 - 2017 ER - TY - JOUR A1 - K. Akiyama A1 - S. Ikeda A1 - M. Pleau A1 - V. L. Fish A1 - F. Tazaki A1 - K. Kuramochi A1 - A. E. Broderick A1 - J. Dexter A1 - M. Mościbrodzka A1 - M. Gowanlock A1 - M. Honma A1 - S. S. Doeleman AU - BT - AJ DO - 10.3847/1538-3881/aa6302 LA - eng PY - 2017 EP - 159 T1 - Superresolution Full-polarimetric Imaging for Radio Interferometry with Sparse Modeling T2 - AJ TI - Superresolution Full-polarimetric Imaging for Radio Interferometry with Sparse Modeling VL - 153 Y1 - 2017 ER - TY - JOUR A1 - K. Akiyama A1 - K. Kuramochi A1 - S. Ikeda A1 - V. L. Fish A1 - F. Tazaki A1 - M. Honma A1 - S. S. Doeleman A1 - A. E. Broderick A1 - J. Dexter A1 - M. Mościbrodzka A1 - K. L. Bouman A1 - A. A. Chael A1 - M. Zaizen AU - BT - ApJ DO - 10.3847/1538-4357/aa6305 LA - eng PY - 2017 EP - 1 T1 - Imaging the Schwarzschild-radius-scale Structure of M87 with the Event Horizon Telescope Using Sparse Modeling T2 - ApJ TI - Imaging the Schwarzschild-radius-scale Structure of M87 with the Event Horizon Telescope Using Sparse Modeling VL - 838 Y1 - 2017 ER - TY - JOUR A1 - K. Hada AU - BT - Galaxies DO - 10.3390/galaxies5010002 LA - eng PY - 2017 EP - 2 T1 - The Structure and Propagation of the Misaligned Jet M87 T2 - Galaxies TI - The Structure and Propagation of the Misaligned Jet M87 VL - 5 Y1 - 2017 ER - TY - JOUR A1 - K. Hada A1 - J. H. Park A1 - M. Kino A1 - K. Niinuma A1 - B. W. Sohn A1 - H. W. Ro A1 - T. Jung A1 - J.-C. Algaba A1 - G.-Y. Zhao A1 - S.-S. Lee A1 - K. Akiyama A1 - S. Trippe A1 - K. Wajima A1 - S. Sawada-Satoh A1 - F. Tazaki A1 - I. Cho A1 - J. Hodgson A1 - J. A. Lee A1 - Y. Hagiwara A1 - M. Honma A1 - S. Koyama A1 - J. Oh A1 - T. Lee A1 - H. Yoo A1 - N. Kawaguchi A1 - D.-G. Roh A1 - S.-J. Oh A1 - J.-H. Yeom A1 - D.-K. Jung A1 - C. Oh A1 - H.-R. Kim A1 - J.-Y. Hwang A1 - D.-Y. Byun A1 - S.-H. Cho A1 - H.-G. Kim A1 - H. Kobayashi A1 - K. M. Shibata AU - BT - PASJ IS - 4 LA - eng PY - 2017 EP - 71 T1 - Pilot KaVA monitoring on the M87 jet: confirming the inner jet structure and superluminal motions at sub-pc scales T2 - PASJ TI - Pilot KaVA monitoring on the M87 jet: confirming the inner jet structure and superluminal motions at sub-pc scales VL - 69 Y1 - 2017 ER - TY - JOUR A1 - B. Boccardi A1 - T. P. Kirchbaum A1 - E. Ros A1 - J. A. Zenzus AU - BT - A&ARv IS - 1 LA - eng PY - 2017 EP - 48 T1 - Radio observations of active galactic nuclei with mm-VLBI T2 - A&ARv TI - Radio observations of active galactic nuclei with mm-VLBI VL - 25 Y1 - 2017 ER - TY - JOUR A1 - C. Goddi A1 - H. Falcke A1 - M. Kramer A1 - L. Rezzolla A1 - C. Brinkerink A1 - BlackHoleCam Collaboration AU - BT - Int. J. Mod. Phys. D IS - 2 LA - eng PY - 2017 EP - 1730001 T1 - BlackHoleCam: Fundamental physics of the galactic center T2 - Int. J. Mod. Phys. D TI - BlackHoleCam: Fundamental physics of the galactic center VL - 26 Y1 - 2017 ER - TY - JOUR A1 - M. D. Johnson A1 - K. L. Bouman A1 - L. L. Blackburn A1 - A. A. Chael A1 - J. Rosen A1 - H. Shiokawa A1 - F. Roelofs A1 - K. Akiyama A1 - V. L. Fish A1 - S. S. Doeleman AU - BT - ApJ IS - 2 LA - eng PY - 2017 EP - 172 T1 - Dynamical Imaging with Interferometry T2 - ApJ TI - Dynamical Imaging with Interferometry VL - 850 Y1 - 2017 ER - TY - JOUR A1 - H. Shiokawa A1 - C. F. Gammie A1 - S. S. Doeleman AU - BT - ApJ IS - 1 LA - eng PY - 2017 EP - 29 T1 - Time Domain Filtering of Resolved Images of Sgr A∗ T2 - ApJ TI - Time Domain Filtering of Resolved Images of Sgr A∗ VL - 846 Y1 - 2017 ER - TY - CONF A1 - M. De Laurentis A1 - Z. Younsi A1 - O. Porth A1 - Y. Mizuno A1 - C. Fromm A1 - L. Rezzolla A1 - H. Olivares AU - BT - JPhCS IS - 012007 LA - eng PY - 2017 T1 - Observational signatures of spherically-symmetric black hole spacetimes T2 - JPhCS TI - Observational signatures of spherically-symmetric black hole spacetimes VL - 942 Y1 - 2017 ER - TY - CONF A1 - H. Falcke AU - BT - JPhCS IS - 012001 LA - eng PY - 2017 T1 - Imaging black holes: past, present and future T2 - JPhCS TI - Imaging black holes: past, present and future VL - 942 Y1 - 2017 ER - TY - JOUR A1 - F. Roelofs A1 - M. D. Johnson A1 - H. Shiokawa A1 - S. S. Doeleman A1 - H. Falcke AU - BT - ApJ IS - 1 LA - eng PY - 2017 EP - 19 T1 - Quantifying Intrinsic Variability of Sagittarius A* Using Closure Phase Measurements of the Event Horizon Telescope T2 - ApJ TI - Quantifying Intrinsic Variability of Sagittarius A* Using Closure Phase Measurements of the Event Horizon Telescope VL - 847 Y1 - 2017 ER - TY - JOUR A1 - R. Gold A1 - J. C. McKinney A1 - M. D. Johnson A1 - S. S. Doeleman AU - BT - ApJ IS - 2 LA - eng PY - 2017 EP - 20 T1 - Probing the Magnetic Field Structure in Sgr A* on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations T2 - ApJ TI - Probing the Magnetic Field Structure in Sgr A* on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations VL - 837 Y1 - 2017 ER - TY - MGZN A1 - S. S. Doeleman AU - BT - Nat. Astro. (Comment) LA - eng PY - 2017 EP - 646 T1 - Seeing the unseeable T2 - Nat. Astro. (Comment) TI - Seeing the unseeable VL - 1 Y1 - 2017 ER - TY - CPAPER A1 - K. L. Bouman A1 - M. D. Johnson A1 - A. V. Dalca A1 - A. A. Chael A1 - F. Roelofs A1 - S. S. Doeleman A1 - W. T. Freeman AU - BT - arXiv e-print LA - eng PY - 2017 T1 - Reconstructing Video from Interferometric Measurements of Time-Varying Sources T2 - arXiv e-print TI - Reconstructing Video from Interferometric Measurements of Time-Varying Sources Y1 - 2017 ER - TY - JOUR A1 - J. Dexter A1 - A. Deller A1 - G. C. Bower A1 - P. Demorest A1 - M. Kramer A1 - B. W. Stappers A1 - A. G. Lyne A1 - M. Kerr A1 - L. G. Spitler A1 - D. Psaltis A1 - M. D. Johnson A1 - R. Narayan AU - BT - MNRAS IS - 3 LA - eng PY - 2017 EP - 3563 T1 - Locating the intense interstellar scattering towards the inner Galaxy T2 - MNRAS TI - Locating the intense interstellar scattering towards the inner Galaxy VL - 471 Y1 - 2017 ER - TY - JOUR A1 - A. A. Chael A1 - R. Narayan A1 - A. Sadowski AU - BT - MNRAS IS - 2 LA - eng PY - 2017 EP - 2367 T1 - Evolving non-thermal electrons in simulations of black hole accretion T2 - MNRAS TI - Evolving non-thermal electrons in simulations of black hole accretion VL - 470 Y1 - 2017 ER - TY - JOUR A1 - L. Medeiros A1 - C.-K. Chan A1 - F. Özel A1 - D. Psaltis A1 - J. Kim A1 - D. P. Marrone A1 - A. Sadowski AU - BT - ApJ IS - 1 LA - eng PY - 2017 EP - 13 T1 - Variability in GRMHD Simulations of Sgr A*: Implications for EHT Closure Phase Observations T2 - ApJ TI - Variability in GRMHD Simulations of Sgr A*: Implications for EHT Closure Phase Observations VL - 844 Y1 - 2017 ER - TY - JOUR A1 - I. Martí-Vidal A1 - A. Roy A1 - J. Conway A1 - A. J. Zensus AU - BT - A&A DO - 10.1051/0004-6361/201526063 LA - eng PY - 2016 EP - A143 T1 - Calibration of mixed-polarization interferometric observations. Tools for the reduction of interferometric data from elements with linear and circular polarization receivers T2 - A&A TI - Calibration of mixed-polarization interferometric observations. Tools for the reduction of interferometric data from elements with linear and circular polarization receivers VL - 587 Y1 - 2016 ER - TY - JOUR A1 - V. L. Fish A1 - M. D. Johnson A1 - S. S. Doeleman A1 - A. E. Broderick A1 - D. Psaltis A1 - R.-S. Lu A1 - K. Akiyama A1 - W. Alef A1 - J. C. Algaba A1 - K. Asada A1 - C. Beaudoin A1 - A. Bertarini A1 - L. Blackburn A1 - R. Blundell A1 - G. C. Bower A1 - C. Brinkerink A1 - R. Cappallo A1 - A. A. Chael A1 - R. Chamberlin A1 - C.-K. Chan A1 - G. B. Crew A1 - J. Dexter A1 - M. Dexter A1 - S. A. Dzib A1 - H. Falcke A1 - R. Freund A1 - P. Friberg A1 - C. H. Greer A1 - M. A. Gurwell A1 - P. T. P. Ho A1 - M. Honma A1 - M. Inoue A1 - T. Johannsen A1 - J. Kim A1 - T. P. Krichbaum A1 - J. Lamb A1 - J. León-Tavares A1 - A. Loeb A1 - L. Loinard A1 - D. MacMahon A1 - D. P. Marrone A1 - J. M. Moran A1 - M. Mościbrodzka A1 - G. N. Ortiz-León A1 - T. Oyama A1 - F. Özel A1 - R. L. Plambeck A1 - N. Pradel A1 - R. A. Primiani A1 - A. E. E. Rogers A1 - K. Rosenfeld A1 - H. Rottmann A1 - A. L. Roy A1 - C. Ruszczyk A1 - D. L. Smythe A1 - J. SooHoo A1 - J. Spilker A1 - J. Stone A1 - P. Strittmatter A1 - R. P. J. Tilanus A1 - M. Titus A1 - L. Vertatschitsch A1 - J. Wagner A1 - J. F. C. Wardle A1 - J. Weintroub A1 - D. Woody A1 - M. Wright A1 - P. Yamaguchi A1 - A. Young A1 - K. H. Young A1 - J. A. Zensus A1 - L. M. Ziurys AU - BT - ApJ DO - 10.3847/0004-637X/820/2/90 LA - eng PY - 2016 EP - 90 T1 - Persistent Asymmetric Structure of Sagittarius A* on Event Horizon Scales T2 - ApJ TI - Persistent Asymmetric Structure of Sagittarius A* on Event Horizon Scales VL - 820 Y1 - 2016 ER - TY - JOUR A1 - A. E. Broderick A1 - V. L. Fish A1 - M. D. Johnson A1 - K. Rosenfeld A1 - C. Wang A1 - S. S. Doeleman A1 - K. Akiyama A1 - T. Johannsen A1 - A. L. Roy AU - BT - ApJ DO - 10.3847/0004-637X/820/2/137 LA - eng PY - 2016 EP - 137 T1 - Modeling Seven Years of Event Horizon Telescope Observations with Radiatively Inefficient Accretion Flow Models T2 - ApJ TI - Modeling Seven Years of Event Horizon Telescope Observations with Radiatively Inefficient Accretion Flow Models VL - 820 Y1 - 2016 ER - TY - JOUR A1 - S. Ikeda A1 - F. Tazaki A1 - K. Akiyama A1 - K. Hada A1 - M. Honma AU - BT - PASJ DO - 10.1093/pasj/psw042 LA - eng PY - 2016 EP - 45 T1 - PRECL: A new method for interferometry imaging from closure phase T2 - PASJ TI - PRECL: A new method for interferometry imaging from closure phase VL - 68 Y1 - 2016 ER - TY - JOUR A1 - K. Akiyama A1 - Stawarz A1 - Y. T. Tanaka A1 - H. Nagai A1 - M. Giroletti A1 - M. Honma AU - BT - ApJ DO - 10.3847/2041-8205/823/2/L26 LA - eng PY - 2016 EP - L26 T1 - EVN Observations of HESS J1943+213: Evidence for an Extreme TeV BL Lac Object T2 - ApJ TI - EVN Observations of HESS J1943+213: Evidence for an Extreme TeV BL Lac Object VL - 823 Y1 - 2016 ER - TY - JOUR A1 - K. Akiyama A1 - M. D. Johnson AU - BT - ApJ DO - 10.3847/2041-8205/824/1/L3 LA - eng PY - 2016 EP - L3 T1 - Interstellar Scintillation and the Radio Counterpart of the Fast Radio Burst FRB 150418 T2 - ApJ TI - Interstellar Scintillation and the Radio Counterpart of the Fast Radio Burst FRB 150418 VL - 824 Y1 - 2016 ER - TY - JOUR A1 - A. Doi A1 - T. Oyama A1 - Y. Kono A1 - A. Yamauchi A1 - S. Suzuki A1 - N. Matsumoto A1 - F. Tazaki AU - BT - PASJ DO - 10.1093/pasj/psw040 LA - eng PY - 2016 EP - 73 T1 - A radio detection survey of narrow-line Seyfert 1 galaxies using very long baseline interferometry at 22 GHz T2 - PASJ TI - A radio detection survey of narrow-line Seyfert 1 galaxies using very long baseline interferometry at 22 GHz VL - 68 Y1 - 2016 ER - TY - JOUR A1 - K. Hada A1 - M. Kino A1 - A. Doi A1 - H. Nagai A1 - M. Honma A1 - K. Akiyama A1 - F. Tazaki A1 - R. Lico A1 - M. Giroletti A1 - G. Giovannini A1 - M. Orienti A1 - Y. Hagiwara AU - BT - ApJ DO - 10.3847/0004-637X/817/2/131 LA - eng PY - 2016 EP - 131 T1 - High-sensitivity 86 GHz (3.5 mm) VLBI Observations of M87: Deep Imaging of the Jet Base at a Resolution of 10 Schwarzschild Radii T2 - ApJ TI - High-sensitivity 86 GHz (3.5 mm) VLBI Observations of M87: Deep Imaging of the Jet Base at a Resolution of 10 Schwarzschild Radii VL - 817 Y1 - 2016 ER - TY - JOUR A1 - S. Nakahara A1 - A. Doi A1 - Y. Murata A1 - K. Hada A1 - M. Nakamura A1 - K. Asada AU - BT - Galaxies DO - 10.3390/galaxies4040080 LA - eng PY - 2016 EP - 80 T1 - Conical Stream of the Two-Sided Jets in NGC 4261 over the Range of 103-109 Schwarzschild Radii T2 - Galaxies TI - Conical Stream of the Two-Sided Jets in NGC 4261 over the Range of 103-109 Schwarzschild Radii VL - 4 Y1 - 2016 ER - TY - CPAPER A1 - Katherine L. Bouman A1 - Michael D. Johnson A1 - Daniel Zoran A1 - Vincent L. Fish A1 - Sheperd S. Doeleman A1 - William T. Freeman AU - BT - The IEEE Conference on Computer Vision and Pattern Recognition (CVPR) DA - 06/2016 LA - eng PY - 2016 T1 - Computational Imaging for VLBI Image Reconstruction T2 - The IEEE Conference on Computer Vision and Pattern Recognition (CVPR) TI - Computational Imaging for VLBI Image Reconstruction Y1 - 2016 ER - TY - JOUR A1 - M. Mościbrodzka A1 - H. Falcke A1 - H. Shiokawa AU - BT - A&A IS - A38 LA - eng PY - 2016 T1 - General relativistic magnetohydrodynamical simulations of the jet in M 87 T2 - A&A TI - General relativistic magnetohydrodynamical simulations of the jet in M 87 VL - 568 Y1 - 2016 ER - TY - JOUR A1 - R. Fraga-Encinas A1 - M. Mościbrodzka A1 - C. Brinkerink A1 - H. Falcke AU - BT - A&A IS - A57 LA - eng PY - 2016 T1 - Probing spacetime around Sagittarius A* using modeled VLBI closure phases T2 - A&A TI - Probing spacetime around Sagittarius A* using modeled VLBI closure phases VL - 588 Y1 - 2016 ER - TY - JOUR A1 - M. D. Johnson AU - BT - ApJ IS - 1 LA - eng PY - 2016 EP - 74 T1 - Stochastic Optics: A Scattering Mitigation Framework for Radio Interferometric Imaging T2 - ApJ TI - Stochastic Optics: A Scattering Mitigation Framework for Radio Interferometric Imaging VL - 833 Y1 - 2016 ER - TY - CONF A1 - M. Backes A1 - C. Müller A1 - J. E. Conway A1 - R. Deane A1 - R. Evans A1 - H. Falcke A1 - R. Fraga-Encinas A1 - C. Goddi A1 - M. Klein Wolt A1 - T. P. Kirchbaum A1 - G. MacLeod A1 - V. A. R. M. Ribeiro A1 - F. Roelofs A1 - Z.-Q. Shen A1 - van H. J. Langevelde AU - BT - 4th Annual Conference on High Energy Astrophysics in Southern Africa (HEASA 2016) CY - Cape Town, South Africa IS - 29 LA - eng PB - South African Astronomical Observatory (SAAO) PP - Cape Town, South Africa PY - 2016 T1 - The Africa Millimetre Telescope T2 - 4th Annual Conference on High Energy Astrophysics in Southern Africa (HEASA 2016) TI - The Africa Millimetre Telescope Y1 - 2016 ER - TY - JOUR A1 - M. D. Johnson A1 - R. Narayan AU - BT - ApJ IS - 2 LA - eng PY - 2016 EP - 10 T1 - The Optics of Refractive Substructure T2 - ApJ TI - The Optics of Refractive Substructure VL - 826 Y1 - 2016 ER - TY - JOUR A1 - T. Johannsen A1 - A. E. Broderick A1 - P. M. Plewa A1 - S. Chatzopoulos A1 - S. S. Doeleman A1 - F. Eisenhauer A1 - V. L. Fish A1 - R. Genzel A1 - O. Gerhard A1 - M. D. Johnson AU - BT - Phys. Rev. Lett. IS - 3 LA - eng PY - 2016 EP - 031101 T1 - Testing General Relativity with the Shadow Size of Sgr A* T2 - Phys. Rev. Lett. TI - Testing General Relativity with the Shadow Size of Sgr A* VL - 116 Y1 - 2016 ER - TY - JOUR A1 - J. Kim A1 - D. P. Marrone A1 - C.-K. Chan A1 - L. Medeiros A1 - F. Özel A1 - D. Psaltis AU - BT - ApJ IS - 2 LA - eng PY - 2016 EP - 156 T1 - Bayesian Techniques for Comparing Time-dependent GRMHD Simulations to Variable Event Horizon Telescope Observations T2 - ApJ TI - Bayesian Techniques for Comparing Time-dependent GRMHD Simulations to Variable Event Horizon Telescope Observations VL - 832 Y1 - 2016 ER - TY - JOUR A1 - D. Psaltis A1 - N. Wex A1 - M. Kramer AU - BT - ApJ IS - 2 LA - eng PY - 2016 EP - 121 T1 - A Quantitative Test of the No-hair Theorem with Sgr A* Using Stars, Pulsars, and the Event Horizon Telescope T2 - ApJ TI - A Quantitative Test of the No-hair Theorem with Sgr A* Using Stars, Pulsars, and the Event Horizon Telescope VL - 818 Y1 - 2016 ER - TY - JOUR A1 - D. Psaltis A1 - F. Özel A1 - C.-K. Chan A1 - D. P. Marrona AU - BT - ApJ IS - 2 LA - eng PY - 2016 EP - 115 T1 - A General Relativistic Null Hypothesis Test with Event Horizon Telescope Observations of the Black Hole Shadow in Sgr A* T2 - ApJ TI - A General Relativistic Null Hypothesis Test with Event Horizon Telescope Observations of the Black Hole Shadow in Sgr A* VL - 814 Y1 - 2016 ER - TY - JOUR A1 - C. D. Brinkerink A1 - C. Müller A1 - H. Falcke A1 - G. C. Bower A1 - T. P. Krichbaum A1 - E. Castillo A1 - A. T. Deller A1 - S. S. Doeleman A1 - R. Fraga-Encinas A1 - C. Goddi A1 - A. Hernández-Gómez A1 - D. H. Hughes A1 - M. Kramer A1 - J. Léon-Tavares A1 - L. Loinard A1 - A. Montaña A1 - M. Mościbrodzka A1 - G. N. Ortiz-León A1 - D. Sanchez-Arguelles A1 - R. P. J. Tilanus A1 - G. W. Wilson A1 - J. A. Zensus AU - BT - MNRAS DO - 10.1093/mnras/stw1743 LA - eng PY - 2016 SP - 1382 EP - 1392 T1 - Asymmetric structure in Sgr A* at 3 mm from closure phase measurements with VLBA, GBT and LMT T2 - MNRAS TI - Asymmetric structure in Sgr A* at 3 mm from closure phase measurements with VLBA, GBT and LMT VL - 462 Y1 - 2016 ER - TY - JOUR A1 - A. A. Chael A1 - M. D. Johnson A1 - R. Narayan A1 - S. S. Doeleman A1 - J. F. C. Wardle A1 - K. L. Bouman AU - BT - ApJ DO - 10.3847/0004-637X/829/1/11 LA - eng PY - 2016 EP - 11 T1 - High-resolution Linear Polarimetric Imaging for the Event Horizon Telescope T2 - ApJ TI - High-resolution Linear Polarimetric Imaging for the Event Horizon Telescope VL - 829 Y1 - 2016 ER - TY - JOUR A1 - T. Johannsen A1 - C. Wang A1 - A. E. Broderick A1 - S. S. Doeleman A1 - V. L. Fish A1 - A. Loeb A1 - D. Psaltis AU - BT - Physical Review Letters DO - 10.1103/PhysRevLett.117.091101 IS - 9 LA - eng PY - 2016 EP - 091101 T1 - Testing General Relativity with Accretion-Flow Imaging of Sgr A* T2 - Physical Review Letters TI - Testing General Relativity with Accretion-Flow Imaging of Sgr A* VL - 117 Y1 - 2016 ER - TY - JOUR A1 - L. Benkevitch A1 - K. Akiyama A1 - R. Lu A1 - S. Doeleman A1 - V. Fish AU - BT - ArXiv e-prints DA - 08/2016 LA - eng PY - 2016 T1 - Reconstruction of Static Black Hole Images Using Simple Geometric Forms T2 - ArXiv e-prints TI - Reconstruction of Static Black Hole Images Using Simple Geometric Forms Y1 - 2016 ER - TY - JOUR A1 - V. L. Fish A1 - K. Akiyama A1 - K. L. Bouman A1 - A. A. Chael A1 - M. D. Johnson A1 - S. S. Doeleman A1 - L. Blackburn A1 - J. F. C. Wardle A1 - W. T. Freeman A1 - the Event Horizon Telescope Collaboration AU - BT - Galaxies IS - 4 LA - eng PY - 2016 EP - 54 T1 - Observing–-and Imaging–-Active Galactic Nuclei with the Event Horizon Telescope T2 - Galaxies TI - Observing–-and Imaging–-Active Galactic Nuclei with the Event Horizon Telescope VL - 4 Y1 - 2016 ER - TY - JOUR A1 - V. L. Fish A1 - M. D. Johnson A1 - S. S. Doeleman A1 - A. E. Broderick A1 - D. Psaltis A1 - R.-S. Lu A1 - K. Akiyama A1 - W. Alef A1 - J. C. Algaba A1 - K. Asada A1 - C. Beaudoin A1 - A. Bertarini A1 - L. Blackburn A1 - R. Blundell A1 - G. C. Bower A1 - C. Brinkerink A1 - R. Cappallo A1 - A. A. Chael A1 - R. Chamberlin A1 - C.-K. Chan A1 - G. B. Crew A1 - J. Dexter A1 - M. Dexter A1 - S. A. Dzib A1 - H. Falcke A1 - R. Freund A1 - P. Friberg A1 - C. H. Greer A1 - M. A. Gurwell A1 - P. T. P. Ho A1 - M. Honma A1 - M. Inoue A1 - T. Johannsen A1 - J. Kim A1 - T. P. Krichbaum A1 - J. Lamb A1 - J. Leon-Tavares A1 - A. Loeb A1 - L. Loinard A1 - D. MacMahon A1 - D. P. Marrone A1 - J. M. Moran A1 - M. Moscibrodzka A1 - G. N. Ortiz-Leon A1 - T. Oyama A1 - F. Ozel A1 - R. L. Plambeck A1 - N. Pradel A1 - R. A. Primiani A1 - A. E. E. Rogers A1 - K. Rosenfeld A1 - H. Rottmann A1 - A. L. Roy A1 - C. Ruszczyk A1 - D. L. Smythe A1 - J. SooHoo A1 - J. Spilker A1 - J. Stone A1 - P. Strittmatter A1 - R. P. J. Tilanus A1 - M. Titus A1 - L. Vertatschitsch A1 - J. Wagner A1 - J. F. C. Wardle A1 - J. Weintroub A1 - D. Woody A1 - M. Wright A1 - P. Yamaguchi A1 - A. Young A1 - K. H. Young A1 - J. A. Zensus A1 - L. M. Ziurys AU - BT - VizieR Online Data Catalog LA - eng PY - 2016 T1 - VizieR Online Data Catalog: 4yr 1.3mm VLBI observations of SgrA* with EHT (Fish+, 2016) T2 - VizieR Online Data Catalog TI - VizieR Online Data Catalog: 4yr 1.3mm VLBI observations of SgrA* with EHT (Fish+, 2016) VL - 182 Y1 - 2016 ER - TY - JOUR A1 - G. N. Ortiz-León A1 - M. D. Johnson A1 - S. S. Doeleman A1 - L. Blackburn A1 - V. L. Fish A1 - L. Loinard A1 - M. J. Reid A1 - E. Castillo A1 - A. A. Chael A1 - A. Hernández-Gómez A1 - D. H. Hughes A1 - J. León-Tavares A1 - R.-S. Lu A1 - A. Montaña A1 - G. Narayanan A1 - K. Rosenfeld A1 - D. Sánchez A1 - F. P. Schloerb A1 - Z.-Q. Shen A1 - H. Shiokawa A1 - J. SooHoo A1 - L. Vertatschitsch AU - BT - ApJ DA - 06/2016 DO - 10.3847/0004-637X/824/1/40 LA - eng PY - 2016 EP - 40 T1 - The Intrinsic Shape of Sagittarius A* at 3.5 mm Wavelength T2 - ApJ TI - The Intrinsic Shape of Sagittarius A* at 3.5 mm Wavelength VL - 824 Y1 - 2016 ER - TY - JOUR A1 - G. C. Bower A1 - A. Deller A1 - P. Demorest A1 - A. Brunthaler A1 - H. Falcke A1 - M. Moscibrodzka A1 - R. M. O'Leary A1 - R. P. Eatough A1 - M. Kramer A1 - K. J. Lee A1 - L. Spitler A1 - G. Desvignes A1 - A. P. Rushton A1 - S. Doeleman A1 - M. J. Reid AU - BT - ApJ DO - 10.3847/0004-637X/821/2/133 LA - eng PY - 2016 EP - 133 T1 - Erratum: "The Proper Motion of the Galactic Center Pulsar Relative to Sagittarius A*" (2015, ApJ, 798, 120)} T2 - ApJ TI - Erratum: "The Proper Motion of the Galactic Center Pulsar Relative to Sagittarius A*" (2015, ApJ, 798, 120)} VL - 821 Y1 - 2016 ER - TY - JOUR A1 - R.-S. Lu A1 - F. Roelofs A1 - V. L. Fish A1 - H. Shiokawa A1 - S. S. Doeleman A1 - C. F. Gammie A1 - H. Falcke A1 - T. P. Krichbaum A1 - J. A. Zensus AU - BT - ApJ DO - 10.3847/0004-637X/817/2/173 LA - eng PY - 2016 EP - 173 T1 - Imaging an Event Horizon: Mitigation of Source Variability of Sagittarius A* T2 - ApJ TI - Imaging an Event Horizon: Mitigation of Source Variability of Sagittarius A* VL - 817 Y1 - 2016 ER - TY - JOUR A1 - R. Gold A1 - J. C. McKinney A1 - M. D. Johnson A1 - S. S. Doeleman AU - BT - ArXiv e-prints LA - eng PY - 2016 T1 - Probing the magnetic field structure in Sgr A* on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations T2 - ArXiv e-prints TI - Probing the magnetic field structure in Sgr A* on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations Y1 - 2016 ER - TY - JOUR A1 - S. Sawada-Satoh A1 - K. Akiyama A1 - K. Niinuma A1 - H. Nagai A1 - M. Kino A1 - F. D'Ammando A1 - S. Koyama A1 - K. Hada A1 - M. Orienti A1 - M. Honma A1 - K. M. Shibata AU - BT - Publication of Korean Astronomical Society DO - 10.5303/PKAS.2015.30.2.429 LA - eng PY - 2015 SP - 429 EP - 432 T1 - Apparent Inward Motion of the Parsec-Scale Jet in the BL Lac Object OJ287 during the 2011-2012 γ-ray Flares T2 - Publication of Korean Astronomical Society TI - Apparent Inward Motion of the Parsec-Scale Jet in the BL Lac Object OJ287 during the 2011-2012 γ-ray Flares VL - 30 Y1 - 2015 ER - TY - JOUR A1 - S. Koyama A1 - M. Kino A1 - A. Doi A1 - K. Niinuma A1 - K. Hada A1 - H. Nagai A1 - M. Honma A1 - K. Akiyama A1 - M. Giroletti A1 - G. Giovannini A1 - M. Orienti A1 - N. Isobe A1 - J. Kataoka A1 - D. Paneque A1 - H. Kobayashi A1 - K. Asada AU - BT - PASJ DO - 10.1093/pasj/psu144 LA - eng PY - 2015 EP - 67 T1 - Probing the precise location of the radio core in the TeV blazar Mrk 501 with VERA at 43 GHz T2 - PASJ TI - Probing the precise location of the radio core in the TeV blazar Mrk 501 with VERA at 43 GHz VL - 67 Y1 - 2015 ER - TY - JOUR A1 - K. Akiyama A1 - R.-S. Lu A1 - V. L. Fish A1 - S. S. Doeleman A1 - A. E. Broderick A1 - J. Dexter A1 - K. Hada A1 - M. Kino A1 - H. Nagai A1 - M. Honma A1 - M. D. Johnson A1 - J. C. Algaba A1 - K. Asada A1 - C. Brinkerink A1 - R. Blundell A1 - G. C. Bower A1 - R. Cappallo A1 - G. B. Crew A1 - M. Dexter A1 - S. A. Dzib A1 - R. Freund A1 - P. Friberg A1 - M. Gurwell A1 - P. T. P. Ho A1 - M. Inoue A1 - T. P. Krichbaum A1 - L. Loinard A1 - D. MacMahon A1 - D. P. Marrone A1 - J. M. Moran A1 - M. Nakamura A1 - N. M. Nagar A1 - G. Ortiz-Leon A1 - R. Plambeck A1 - N. Pradel A1 - R. A. Primiani A1 - A. E. E. Rogers A1 - A. L. Roy A1 - J. SooHoo A1 - J.-L. Tavares A1 - R. P. J. Tilanus A1 - M. Titus A1 - J. Wagner A1 - J. Weintroub A1 - P. Yamaguchi A1 - K. H. Young A1 - A. Zensus A1 - L. M. Ziurys AU - BT - ApJ DO - 10.1088/0004-637X/807/2/150 LA - eng PY - 2015 EP - 150 T1 - 230 GHz VLBI Observations of M87: Event-horizon-scale Structure during an Enhanced Very-high-energy γ-Ray State in 2012 T2 - ApJ TI - 230 GHz VLBI Observations of M87: Event-horizon-scale Structure during an Enhanced Very-high-energy γ-Ray State in 2012 VL - 807 Y1 - 2015 ER - TY - JOUR A1 - K. Niinuma A1 - M. Kino A1 - A. Doi A1 - K. Hada A1 - H. Nagai A1 - S. Koyama AU - BT - ApJ DO - 10.1088/2041-8205/807/1/L14 LA - eng PY - 2015 EP - L14 T1 - Discovery of a Wandering Radio Jet Base after a Large X-Ray Flare in the Blazar Markarian 421 T2 - ApJ TI - Discovery of a Wandering Radio Jet Base after a Large X-Ray Flare in the Blazar Markarian 421 VL - 807 Y1 - 2015 ER - TY - JOUR A1 - M. Kino A1 - F. Takahara A1 - K. Hada A1 - K. Akiyama A1 - H. Nagai A1 - B. W. Sohn AU - BT - ApJ DO - 10.1088/0004-637X/803/1/30 LA - eng PY - 2015 EP - 30 T1 - Magnetization Degree at the Jet Base of M87 Derived from the Event Horizon Telescope Data: Testing the Magnetically Driven Jet Paradigm T2 - ApJ TI - Magnetization Degree at the Jet Base of M87 Derived from the Event Horizon Telescope Data: Testing the Magnetically Driven Jet Paradigm VL - 803 Y1 - 2015 ER - TY - JOUR A1 - C.-K. Chan A1 - D. Psaltis A1 - F. Özel A1 - L. Medeiros A1 - D. P. Marrone A1 - A. Sadowski A1 - R. Narayan AU - BT - ApJ IS - 2 LA - eng PY - 2015 EP - 103 T1 - Fast Variability and Millimeter/IR Flares in GRMHD Models of Sgr A* from Strong-field Gravitational Lensing T2 - ApJ TI - Fast Variability and Millimeter/IR Flares in GRMHD Models of Sgr A* from Strong-field Gravitational Lensing VL - 812 Y1 - 2015 ER - TY - JOUR A1 - C.-K. Chan A1 - D. Psaltis A1 - F. Özel A1 - R. Narayan A1 - A. Sadowski AU - BT - ApJ IS - 1 LA - eng PY - 2015 EP - 1 T1 - The Power of Imaging: Constraining the Plasma Properties of GRMHD Simulations using EHT Observations of Sgr A* T2 - ApJ TI - The Power of Imaging: Constraining the Plasma Properties of GRMHD Simulations using EHT Observations of Sgr A* VL - 799 Y1 - 2015 ER - TY - JOUR A1 - D. Psaltis A1 - R. Narayan A1 - V. L. Fish A1 - A. E. Broderick A1 - A. Loeb A1 - S. S. Doeleman AU - BT - ApJ IS - 1 LA - eng PY - 2015 EP - 15 T1 - Event Horizon Telescope Evidence for Alignment of the Black Hole in the Center of the Milky Way with the Inner Stellar Disk T2 - ApJ TI - Event Horizon Telescope Evidence for Alignment of the Black Hole in the Center of the Milky Way with the Inner Stellar Disk VL - 798 Y1 - 2015 ER - TY - JOUR A1 - M. D. Johnson A1 - V. L. Fish A1 - S. S. Doeleman A1 - D. P. Marrone A1 - R. L. Plambeck A1 - J. F. C. Wardle A1 - K. Akiyama A1 - K. Asada A1 - C. Beaudoin A1 - L. Blackburn A1 - R. Blundell A1 - G. C. Bower A1 - C. Brinkerink A1 - A. E. Broderick A1 - R. Cappallo A1 - A. A. Chael A1 - G. B. Crew A1 - J. Dexter A1 - M. Dexter A1 - R. Freund A1 - P. Friberg A1 - R. Gold A1 - M. A. Gurwell A1 - P. T. P. Ho A1 - M. Honma A1 - M. Inoue A1 - M. Kosowsky A1 - T. P. Krichbaum A1 - J. Lamb A1 - A. Loeb A1 - R.-S. Lu A1 - D. MacMahon A1 - J. C. McKinney A1 - J. M. Moran A1 - R. Narayan A1 - R. A. Primiani A1 - D. Psaltis A1 - A. E. E. Rogers A1 - K. Rosenfeld A1 - J. SooHoo A1 - R. P. J. Tilanus A1 - M. Titus A1 - L. Vertatschitsch A1 - J. Weintroub A1 - M. Wright A1 - K. H. Young A1 - J. A. Zensus A1 - L. M. Ziurys AU - BT - Science DO - 10.1126/science.aac7087 LA - eng PY - 2015 SP - 1242 EP - 1245 T1 - Resolved magnetic-field structure and variability near the event horizon of Sagittarius A* T2 - Science TI - Resolved magnetic-field structure and variability near the event horizon of Sagittarius A* VL - 350 Y1 - 2015 ER - TY - JOUR A1 - L. Vertatschitsch A1 - R. Primiani A1 - A. Young A1 - J. Weintroub A1 - G. B. Crew A1 - S. R. McWhirter A1 - C. Beaudoin A1 - S. Doeleman A1 - L. Blackburn AU - BT - PASP DA - 12/2015 DO - 10.1086/684513 LA - eng PY - 2015 SP - 1226 EP - 1239 T1 - R2DBE: A Wideband Digital Backend for the Event Horizon Telescope T2 - PASP TI - R2DBE: A Wideband Digital Backend for the Event Horizon Telescope VL - 127 Y1 - 2015 ER - TY - JOUR A1 - F. Ruesink A1 - H. M. Doeleman A1 - R. Hendrikx A1 - A. F. Koenderink A1 - E. Verhagen AU - BT - Physical Review Letters DO - 10.1103/PhysRevLett.115.203904 IS - 20 LA - eng PY - 2015 EP - 203904 T1 - Perturbing Open Cavities: Anomalous Resonance Frequency Shifts in a Hybrid Cavity-Nanoantenna System T2 - Physical Review Letters TI - Perturbing Open Cavities: Anomalous Resonance Frequency Shifts in a Hybrid Cavity-Nanoantenna System VL - 115 Y1 - 2015 ER - TY - JOUR A1 - M. D. Johnson A1 - A. Loeb A1 - H. Shiokawa A1 - A. A. Chael A1 - S. S. Doeleman AU - BT - ApJ DA - 11/2015 DO - 10.1088/0004-637X/813/2/132 LA - eng PY - 2015 EP - 132 T1 - Measuring the Direction and Angular Velocity of a Black Hole Accretion Disk via Lagged Interferometric Covariance T2 - ApJ TI - Measuring the Direction and Angular Velocity of a Black Hole Accretion Disk via Lagged Interferometric Covariance VL - 813 Y1 - 2015 ER - TY - JOUR A1 - J. Wagner A1 - A. L. Roy A1 - T. P. Krichbaum A1 - W. Alef A1 - A. Bansod A1 - A. Bertarini A1 - R. Güsten A1 - D. Graham A1 - J. Hodgson A1 - R. Märtens A1 - K. Menten A1 - D. Muders A1 - H. Rottmann A1 - G. Tuccari A1 - A. Weiss A1 - G. Wieching A1 - M. Wunderlich A1 - J. A. Zensus A1 - J. P. Araneda A1 - O. Arriagada A1 - M. Cantzler A1 - C. Duran A1 - F. M. Montenegro-Montes A1 - R. Olivares A1 - P. Caro A1 - P. Bergman A1 - J. Conway A1 - R. Haas A1 - J. Johansson A1 - M. Lindqvist A1 - H. Olofsson A1 - M. Pantaleev A1 - S. Buttaccio A1 - R. Cappallo A1 - G. Crew A1 - S. Doeleman A1 - V. Fish A1 - R.-S. Lu A1 - C. Ruszczyk A1 - J. SooHoo A1 - M. Titus A1 - R. Freund A1 - D. Marrone A1 - P. Strittmatter A1 - L. Ziurys A1 - R. Blundell A1 - R. Primiani A1 - J. Weintroub A1 - K. Young A1 - M. Bremer A1 - S. Sánchez A1 - A. P. Marscher A1 - R. Chilson A1 - K. Asada A1 - M. Inoue AU - BT - A&A DA - 09/2015 DO - 10.1051/0004-6361/201423613 LA - eng PY - 2015 EP - A32 T1 - First 230 GHz VLBI fringes on 3C 279 using the APEX Telescope T2 - A&A TI - First 230 GHz VLBI fringes on 3C 279 using the APEX Telescope VL - 581 Y1 - 2015 ER - TY - JOUR A1 - A. Chael A1 - S. Doeleman A1 - M. D. Johnson AU - BT - IAU General Assembly DA - 08/2015 LA - eng PY - 2015 EP - 2258350 T1 - Imaging Black Hole Magnetic Fields with the Event Horizon Telescope T2 - IAU General Assembly TI - Imaging Black Hole Magnetic Fields with the Event Horizon Telescope VL - 22 Y1 - 2015 ER - TY - JOUR A1 - M. D. Johnson A1 - S. S. Doeleman A1 - Event Horizon Telescope Collaboration AU - BT - IAU General Assembly DA - 08/2015 LA - eng PY - 2015 EP - 2257792 T1 - The Event Horizon Telescope: New Developments and Results T2 - IAU General Assembly TI - The Event Horizon Telescope: New Developments and Results VL - 22 Y1 - 2015 ER - TY - JOUR A1 - K. Niinuma A1 - S.-S. Lee A1 - M. Kino A1 - B. W. Sohn A1 - K. Akiyama A1 - G.-Y. Zhao A1 - S. Sawada-Satoh A1 - S. Trippe A1 - K. Hada A1 - T. Jung A1 - Y. Hagiwara A1 - R. Dodson A1 - S. Koyama A1 - M. Honma A1 - H. Nagai A1 - A. Chung A1 - A. Doi A1 - K. Fujisawa A1 - M.-H. Han A1 - J.-S. Kim A1 - J. Lee A1 - J. A. Lee A1 - A. Miyazaki A1 - T. Oyama A1 - K. Sorai A1 - K. Wajima A1 - J. Bae A1 - D.-Y. Byun A1 - S.-H. Cho A1 - Y. K. Choi A1 - H. Chung A1 - M.-H. Chung A1 - S.-T. Han A1 - T. Hirota A1 - J.-W. Hwang A1 - D.-H. Je A1 - T. Jike A1 - D.-K. Jung A1 - J.-S. Jung A1 - J.-H. Kang A1 - J. Kang A1 - Y.-W. Kang A1 - Y. Kan-ya A1 - M. Kanaguchi A1 - N. Kawaguchi A1 - B. G. Kim A1 - H. R. Kim A1 - H.-G. Kim A1 - J. Kim A1 - J. Kim A1 - K.-T. Kim A1 - M. Kim A1 - H. Kobayashi A1 - Y. Kono A1 - T. Kurayama A1 - C. Lee A1 - J.-W. Lee A1 - S. H. Lee A1 - Y. C. Minh A1 - N. Matsumoto A1 - A. Nakagawa A1 - C. S. Oh A1 - S.-J. Oh A1 - S.-Y. Park A1 - D.-G. Roh A1 - T. Sasao A1 - K. M. Shibata A1 - M.-G. Song A1 - Y. Tamura A1 - S.-O. Wi A1 - J.-H. Yeom A1 - Y. J. Yun AU - BT - PASJ DO - 10.1093/pasj/psu104 LA - eng PY - 2014 EP - 103 T1 - VLBI observations of bright AGN jets with the KVN and VERA Array (KaVA): Evaluation of imaging capability T2 - PASJ TI - VLBI observations of bright AGN jets with the KVN and VERA Array (KaVA): Evaluation of imaging capability VL - 66 Y1 - 2014 ER - TY - JOUR A1 - M. Honma A1 - K. Akiyama A1 - M. Uemura A1 - S. Ikeda AU - BT - PASJ DO - 10.1093/pasj/psu070 LA - eng PY - 2014 EP - 95 T1 - Super-resolution imaging with radio interferometry using sparse modeling T2 - PASJ TI - Super-resolution imaging with radio interferometry using sparse modeling VL - 66 Y1 - 2014 ER - TY - JOUR A1 - K. Hada A1 - M. Giroletti A1 - M. Kino A1 - G. Giovannini A1 - F. D'Ammando A1 - C. C. Cheung A1 - M. Beilicke A1 - H. Nagai A1 - A. Doi A1 - K. Akiyama A1 - M. Honma A1 - K. Niinuma A1 - C. Casadio A1 - M. Orienti A1 - H. Krawczynski A1 - J. L. Gómez A1 - S. Sawada-Satoh A1 - S. Koyama A1 - A. Cesarini A1 - S. Nakahara A1 - M. A. Gurwell AU - BT - ApJ DO - 10.1088/0004-637X/788/2/165 LA - eng PY - 2014 EP - 165 T1 - A Strong Radio Brightening at the Jet Base of M 87 during the Elevated Very High Energy Gamma-Ray State in 2012 T2 - ApJ TI - A Strong Radio Brightening at the Jet Base of M 87 during the Elevated Very High Energy Gamma-Ray State in 2012 VL - 788 Y1 - 2014 ER - TY - JOUR A1 - M. Kino A1 - F. Takahara A1 - K. Hada A1 - A. Doi AU - BT - ApJ DO - 10.1088/0004-637X/786/1/5 LA - eng PY - 2014 EP - 5 T1 - Relativistic Electrons and Magnetic Fields of the M87 Jet on the \~10 Schwarzschild Radii Scale T2 - ApJ TI - Relativistic Electrons and Magnetic Fields of the M87 Jet on the \~10 Schwarzschild Radii Scale VL - 786 Y1 - 2014 ER - TY - JOUR A1 - C. Y. Kuo A1 - K. Asada A1 - R. Rao A1 - M. Nakamura A1 - J. C. Algaba A1 - H. B. Liu A1 - M. Inoue A1 - P. M. Koch A1 - P. T. P. Ho A1 - S. Matsushita A1 - H.-Y. Pu A1 - K. Akiyama A1 - H. Nishioka A1 - N. Pradel AU - BT - ApJ DO - 10.1088/2041-8205/783/2/L33 LA - eng PY - 2014 EP - L33 T1 - Measuring Mass Accretion Rate onto the Supermassive Black Hole in M87 Using Faraday Rotation Measure with the Submillimeter Array T2 - ApJ TI - Measuring Mass Accretion Rate onto the Supermassive Black Hole in M87 Using Faraday Rotation Measure with the Submillimeter Array VL - 783 Y1 - 2014 ER - TY - JOUR A1 - M. J. Reid A1 - M. Honma AU - BT - ARA&A DO - 10.1146/annurev-astro-081913-040006 LA - eng PY - 2014 SP - 339 EP - 372 T1 - Microarcsecond Radio Astrometry T2 - ARA&A TI - Microarcsecond Radio Astrometry VL - 52 Y1 - 2014 ER - TY - JOUR A1 - A. E. Broderick A1 - T. Johannsen A1 - A. Loeb A1 - D. Psaltis AU - BT - ApJ IS - 1 LA - eng PY - 2014 EP - 7 T1 - Testing the No-hair Theorem with Event Horizon Telescope Observations of Sagittarius A* T2 - ApJ TI - Testing the No-hair Theorem with Event Horizon Telescope Observations of Sagittarius A* VL - 784 Y1 - 2014 ER - TY - JOUR A1 - M. Nakamura A1 - K. Asada AB - The structure and dynamics of the M87 jet from sub-milliarcsec to arcsecond scales are continuously examined. We analyzed the Very Long Baseline Array archival data taken at 43 and 86 GHz to measure the size of very long baseline interferometry (VLBI) cores. Millimeter/sub-millimeter VLBI cores are considered as innermost jet emissions, which has been originally suggested by Blandford & Königl. Those components fairly follow an extrapolated parabolic streamline in our previous study so that the jet has a single power-law structure with nearly 5 orders of magnitude in the distance starting from the vicinity of the supermassive black hole (SMBH), less than 10 Schwarzschild radius (r s). We further inspect the jet parabolic structure as a counterpart of the magnetohydrodynamic (MHD) nozzle in order to identify the property of a bulk acceleration. We interpret that the parabolic jet consists of Poynting-flux dominated flows, powered by large-amplitude, nonlinear torsional Alfvén waves. We examine the non-relativistic MHD nozzle equation in a parabolic shape. The nature of trans-fast magnetosonic flow is similar to the one of transonic solution of Parker's hydrodynamic solar wind; the jet becomes super-escape as well as super-fast magnetosonic at around ~103 r s, while the upstream trans-Alfvénic flow speed increases linearly as a function of the distance at ~102-103 r s. We here point out that this is the first evidence to identify these features in astrophysical jets. We propose that the M87 jet is magnetically accelerated, but thermally confined by the stratified interstellar medium inside the sphere of gravitational influence of the SMBH potential, which may be a norm in active galactic nucleus jets. AU - BT - ApJ DO - 10.1088/0004-637X/775/2/118 LA - eng N2 - The structure and dynamics of the M87 jet from sub-milliarcsec to arcsecond scales are continuously examined. We analyzed the Very Long Baseline Array archival data taken at 43 and 86 GHz to measure the size of very long baseline interferometry (VLBI) cores. Millimeter/sub-millimeter VLBI cores are considered as innermost jet emissions, which has been originally suggested by Blandford & Königl. Those components fairly follow an extrapolated parabolic streamline in our previous study so that the jet has a single power-law structure with nearly 5 orders of magnitude in the distance starting from the vicinity of the supermassive black hole (SMBH), less than 10 Schwarzschild radius (r s). We further inspect the jet parabolic structure as a counterpart of the magnetohydrodynamic (MHD) nozzle in order to identify the property of a bulk acceleration. We interpret that the parabolic jet consists of Poynting-flux dominated flows, powered by large-amplitude, nonlinear torsional Alfvén waves. We examine the non-relativistic MHD nozzle equation in a parabolic shape. The nature of trans-fast magnetosonic flow is similar to the one of transonic solution of Parker's hydrodynamic solar wind; the jet becomes super-escape as well as super-fast magnetosonic at around ~103 r s, while the upstream trans-Alfvénic flow speed increases linearly as a function of the distance at ~102-103 r s. We here point out that this is the first evidence to identify these features in astrophysical jets. We propose that the M87 jet is magnetically accelerated, but thermally confined by the stratified interstellar medium inside the sphere of gravitational influence of the SMBH potential, which may be a norm in active galactic nucleus jets. PY - 2013 EP - 118 T1 - The Parabolic Jet Structure in M87 as a Magnetohydrodynamic Nozzle T2 - ApJ TI - The Parabolic Jet Structure in M87 as a Magnetohydrodynamic Nozzle VL - 775 Y1 - 2013 ER - TY - JOUR A1 - K. Hada A1 - M. Kino A1 - A. Doi A1 - H. Nagai A1 - M. Honma A1 - Y. Hagiwara A1 - M. Giroletti A1 - G. Giovannini A1 - N. Kawaguchi AU - BT - ApJ DO - 10.1088/0004-637X/775/1/70 LA - eng PY - 2013 EP - 70 T1 - The Innermost Collimation Structure of the M87 Jet Down to \~10 Schwarzschild Radii T2 - ApJ TI - The Innermost Collimation Structure of the M87 Jet Down to \~10 Schwarzschild Radii VL - 775 Y1 - 2013 ER - TY - JOUR A1 - K. Hada A1 - A. Doi A1 - H. Nagai A1 - M. Inoue A1 - M. Honma A1 - M. Giroletti A1 - G. Giovannini AU - BT - ApJ DO - 10.1088/0004-637X/779/1/6 LA - eng PY - 2013 EP - 6 T1 - Evidence for a Nuclear Radio Jet and its Structure down to lsim100 Schwarzschild Radii in the Center of the Sombrero Galaxy (M 104, NGC 4594) T2 - ApJ TI - Evidence for a Nuclear Radio Jet and its Structure down to lsim100 Schwarzschild Radii in the Center of the Sombrero Galaxy (M 104, NGC 4594) VL - 779 Y1 - 2013 ER - TY - JOUR A1 - K. Akiyama A1 - R. Takahashi A1 - M. Honma A1 - T. Oyama A1 - H. Kobayashi AU - BT - PASJ DO - 10.1093/pasj/65.4.91 LA - eng PY - 2013 EP - 91 T1 - Multi-Epoch VERA Observations of Sagittarius A*. I. Images and Structural Variability T2 - PASJ TI - Multi-Epoch VERA Observations of Sagittarius A*. I. Images and Structural Variability VL - 65 Y1 - 2013 ER - TY - JOUR A1 - A. Doi A1 - Y. Murata A1 - N. Mochizuki A1 - H. Takeuchi A1 - K. Asada A1 - T. J. Hayashi A1 - H. Nagai A1 - K. M. Shibata A1 - T. Oyama A1 - T. Jike A1 - K. Fujisawa A1 - K. Sugiyama A1 - H. Ogawa A1 - K. Kimura A1 - M. Honma A1 - H. Kobayashi A1 - S. Koyama AU - BT - PASJ DO - 10.1093/pasj/65.3.57 LA - eng PY - 2013 EP - 57 T1 - Multifrequency VLBI Observations of the Broad Absorption Line Quasar J1020+4320: Recently Restarted Jet Activity? T2 - PASJ TI - Multifrequency VLBI Observations of the Broad Absorption Line Quasar J1020+4320: Recently Restarted Jet Activity? VL - 65 Y1 - 2013 ER - TY - JOUR A1 - H. Nagai A1 - M. Kino A1 - K. Niinuma A1 - K. Akiyama A1 - K. Hada A1 - S. Koyama A1 - M. Orienti A1 - K. Hiura A1 - S. Sawada-Satoh A1 - M. Honma A1 - G. Giovannini A1 - M. Giroletti A1 - K. Shibata A1 - K. Sorai AU - BT - PASJ DO - 10.1093/pasj/65.2.24 LA - eng PY - 2013 EP - 24 T1 - The GENJI Programme: Gamma-Ray Emitting Notable AGN Monitoring by Japanese VLBI T2 - PASJ TI - The GENJI Programme: Gamma-Ray Emitting Notable AGN Monitoring by Japanese VLBI VL - 65 Y1 - 2013 ER - TY - JOUR A1 - R.-S. Lu A1 - V. L. Fish A1 - K. Akiyama A1 - S. S. Doeleman A1 - J. C. Algaba A1 - G. C. Bower A1 - C. Brinkerink A1 - R. Chamberlin A1 - G. Crew A1 - R. J. Cappallo A1 - M. Dexter A1 - R. Freund A1 - P. Friberg A1 - M. A. Gurwell A1 - P. T. P. Ho A1 - M. Honma A1 - M. Inoue A1 - S. G. Jorstad A1 - T. P. Krichbaum A1 - L. Loinard A1 - D. MacMahon A1 - D. P. Marrone A1 - A. P. Marscher A1 - J. M. Moran A1 - R. Plambeck A1 - N. Pradel A1 - R. Primiani A1 - R. P. J. Tilanus A1 - M. Titus A1 - J. Weintroub A1 - M. Wright A1 - K. H. Young A1 - L. M. Ziurys AU - BT - ApJ DO - 10.1088/0004-637X/772/1/13 LA - eng PY - 2013 EP - 13 T1 - Fine-scale Structure of the Quasar 3C 279 Measured with 1.3 mm Very Long Baseline Interferometry T2 - ApJ TI - Fine-scale Structure of the Quasar 3C 279 Measured with 1.3 mm Very Long Baseline Interferometry VL - 772 Y1 - 2013 ER - TY - JOUR A1 - et V. L. Fish al. AU - BT - ArXiv e-print LA - eng PY - 2013 T1 - High-Angular-Resolution and High-Sensitivity Science Enabled by Beamformed ALMA T2 - ArXiv e-print TI - High-Angular-Resolution and High-Sensitivity Science Enabled by Beamformed ALMA Y1 - 2013 ER - TY - JOUR A1 - C.-K. Chan A1 - D. Psaltis A1 - F. Özel AU - BT - ApJ IS - 1 LA - eng PY - 2013 EP - 13 T1 - GRay: A Massively Parallel GPU-based Code for Ray Tracing in Relativistic Spacetimes T2 - ApJ TI - GRay: A Massively Parallel GPU-based Code for Ray Tracing in Relativistic Spacetimes VL - 777 Y1 - 2013 ER - TY - JOUR A1 - K. Hada A1 - M. Kino A1 - H. Nagai A1 - A. Doi A1 - Y. Hagiwara A1 - M. Honma A1 - M. Giroletti A1 - G. Giovannini A1 - N. Kawaguchi AU - BT - ApJ DO - 10.1088/0004-637X/760/1/52 LA - eng PY - 2012 EP - 52 T1 - VLBI Observations of the Jet in M 87 during the Very High Energy γ-Ray Flare in 2010 April T2 - ApJ TI - VLBI Observations of the Jet in M 87 during the Very High Energy γ-Ray Flare in 2010 April VL - 760 Y1 - 2012 ER - TY - JOUR A1 - M. Giroletti A1 - K. Hada A1 - G. Giovannini A1 - C. Casadio A1 - M. Beilicke A1 - A. Cesarini A1 - C. C. Cheung A1 - A. Doi A1 - H. Krawczynski A1 - M. Kino A1 - N. P. Lee A1 - H. Nagai AU - BT - A&A DO - 10.1051/0004-6361/201218794 LA - eng PY - 2012 EP - L10 T1 - The kinematic of HST-1 in the jet of M 87 T2 - A&A TI - The kinematic of HST-1 in the jet of M 87 VL - 538 Y1 - 2012 ER - TY - JOUR A1 - R.-S. Lu A1 - V. L. Fish A1 - J. Weintraub A1 - S. S. Doeleman A1 - G. C. Bower A1 - R. Freund A1 - P. Friberg A1 - P. T. P. Ho A1 - M. Honma A1 - M. Inoue A1 - T. P. Kirchbaum A1 - D. P. Marrone A1 - J. M. Moran A1 - T. Oyama A1 - R. Plambeck A1 - R. Primiani A1 - Z.-Q. Shen A1 - R. P. J. Tilanus A1 - M. Wright A1 - K. H. Young A1 - L. M. Ziurys A1 - A. J. Zenzus AU - BT - ApJ (Letter) IS - 1 LA - eng PY - 2012 EP - 5 T1 - Resolving the Inner Jet Structure of 1924-292 with the Event Horizon Telescope T2 - ApJ (Letter) TI - Resolving the Inner Jet Structure of 1924-292 with the Event Horizon Telescope VL - 757 Y1 - 2012 ER - TY - JOUR A1 - S. S. Doeleman A1 - V. L. Fish A1 - et D. E. Schenck al. AU - BT - Science IS - 6105 LA - eng PY - 2012 EP - 355 T1 - Jet-Launching Structure Resolved Near the Supermassive Black Hole in M87 T2 - Science TI - Jet-Launching Structure Resolved Near the Supermassive Black Hole in M87 VL - 338 Y1 - 2012 ER - TY - MGZN A1 - H. Falcke A1 - R. Laing A1 - L. Testi A1 - A. J. Zenzus AU - BT - Messenger LA - eng PY - 2012 EP - 50 T1 - Report on the ESO Workshop ''mm-wave VLBI with ALMA and Radio Telescopes around the World'' T2 - Messenger TI - Report on the ESO Workshop ''mm-wave VLBI with ALMA and Radio Telescopes around the World'' VL - 149 Y1 - 2012 ER - TY - JOUR A1 - T. Johannsen A1 - D. Psaltis A1 - S. Gillessen A1 - D. P. Marrone A1 - F. Özel A1 - S. S. Doeleman A1 - V. L. Fish AU - BT - ApJ IS - 1 LA - eng PY - 2012 EP - 30 T1 - Masses of nearby Supermassive Black Holes with Very Long Baseline Interferometry T2 - ApJ TI - Masses of nearby Supermassive Black Holes with Very Long Baseline Interferometry VL - 758 Y1 - 2012 ER - TY - JOUR A1 - D. Psaltis A1 - T. Johannsen AU - BT - ApJ IS - 1 LA - eng PY - 2012 EP - 1 T1 - A Ray-tracing Algorithm for Spinning Compact Object Spacetimes with Arbitrary Quadrupole Moments. I. Quasi-Kerr Black Holes T2 - ApJ TI - A Ray-tracing Algorithm for Spinning Compact Object Spacetimes with Arbitrary Quadrupole Moments. I. Quasi-Kerr Black Holes VL - 745 Y1 - 2012 ER - TY - JOUR A1 - K. Hada A1 - A. Doi A1 - M. Kino A1 - H. Nagai A1 - Y. Hagiwara A1 - N. Kawaguchi AU - BT - Nature DO - 10.1038/nature10387 LA - eng PY - 2011 SP - 185 EP - 187 T1 - An origin of the radio jet in M87 at the location of the central black hole T2 - Nature TI - An origin of the radio jet in M87 at the location of the central black hole VL - 477 Y1 - 2011 ER - TY - JOUR A1 - V. L. Fish A1 - et S. S. Doleman al. AU - BT - ApJ IS - 2 LA - eng PY - 2011 EP - 36 T1 - 1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-variable Emission on Event Horizon Scales T2 - ApJ TI - 1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-variable Emission on Event Horizon Scales VL - 727 Y1 - 2011 ER - TY - JOUR A1 - T. Johannsen A1 - D. Psaltis AU - BT - ApJ IS - 1 LA - eng PY - 2011 EP - 11 T1 - Testing the No-hair Theorem with Observations in the Electromagnetic Spectrum. III. Quasi-periodic Variability T2 - ApJ TI - Testing the No-hair Theorem with Observations in the Electromagnetic Spectrum. III. Quasi-periodic Variability VL - 726 Y1 - 2011 ER - TY - JOUR A1 - T. Johannsen A1 - D. Psaltis AU - BT - ApJ IS - 1 LA - eng PY - 2010 EP - 446 T1 - Testing the No-hair Theorem with Observations in the Electromagnetic Spectrum. II. Black Hole Images T2 - ApJ TI - Testing the No-hair Theorem with Observations in the Electromagnetic Spectrum. II. Black Hole Images VL - 718 Y1 - 2010 ER - TY - JOUR A1 - T. Johannsen A1 - D. Psaltis AU - BT - ApJ IS - 1 LA - eng PY - 2010 EP - 187 T1 - Testing the No-hair Theorem with Observations in the Electromagnetic Spectrum. I. Properties of a Quasi-Kerr Spacetime T2 - ApJ TI - Testing the No-hair Theorem with Observations in the Electromagnetic Spectrum. I. Properties of a Quasi-Kerr Spacetime VL - 716 Y1 - 2010 ER - TY - JOUR A1 - S. S. Doeleman A1 - V. L. Fish A1 - A. E. Broderick A1 - A. Loeb A1 - A. E. E. Rogers AU - BT - ApJ IS - 1 LA - eng PY - 2009 EP - 59 T1 - Detecting Flaring Structures in Sagittarius A* with High-Frequency VLBI T2 - ApJ TI - Detecting Flaring Structures in Sagittarius A* with High-Frequency VLBI VL - 695 Y1 - 2009 ER - TY - JOUR A1 - A. E. Broderick A1 - A. Loeb AU - BT - ApJ IS - 2 LA - eng PY - 2009 EP - 1164 T1 - Imaging the Black Hole Silhouette of M87: Implications for Jet Formation and Black Hole Spin T2 - ApJ TI - Imaging the Black Hole Silhouette of M87: Implications for Jet Formation and Black Hole Spin VL - 697 Y1 - 2009 ER - TY - JOUR A1 - et S. S. Doeleman al. AU - BT - Nature LA - eng PY - 2009 EP - 78 T1 - Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre T2 - Nature TI - Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre VL - 455 Y1 - 2009 ER - TY - JOUR A1 - et S. S. Doeleman al. AU - BT - Science White Paper submitted to the ASTRO2010 Decadal Review Panels LA - eng PY - 2009 T1 - Imaging an Event Horizon: submm-VLBI of a Super Massive Black Hole T2 - Science White Paper submitted to the ASTRO2010 Decadal Review Panels TI - Imaging an Event Horizon: submm-VLBI of a Super Massive Black Hole Y1 - 2009 ER - TY - JOUR A1 - C.-K. Chan A1 - S. Liu A1 - C. L. Fryer A1 - D. Psaltis A1 - F. Özel A1 - G. Rockefeller A1 - F. Melia AU - BT - ApJ IS - 1 LA - eng PY - 2009 EP - 512 T1 - MHD Simulations of Accretion onto Sgr A*: Quiescent Fluctuations, Outbursts, and Quasiperiodicity T2 - ApJ TI - MHD Simulations of Accretion onto Sgr A*: Quiescent Fluctuations, Outbursts, and Quasiperiodicity VL - 701 Y1 - 2009 ER - TY - JOUR A1 - T. P. Kirchbaum A1 - D. A. Graham A1 - A. Witzel A1 - A. Greve A1 - J. E. Wink A1 - M. Grewing A1 - F. Colomer A1 - de P. Vicente A1 - J. Gomez-Gonzalez A1 - A. Baudry A1 - J. A. Zenzus AU - BT - A&A (Letter) LA - eng PY - 1998 EP - 106 T1 - VLBI observations of the galactic center source Sgr A* at 86 GHz and 215 GHz T2 - A&A (Letter) TI - VLBI observations of the galactic center source Sgr A* at 86 GHz and 215 GHz VL - 335 Y1 - 1998 ER - TY - JOUR A1 - T. P. Kirchbaum A1 - D. A. Graham A1 - A. Greve A1 - J. E. Wink A1 - J. Alcolea A1 - F. Colomer A1 - de P. Vicente A1 - A. Baudry A1 - J. Gomez-Gonzalez A1 - M. Grewing A1 - A. Witzel AU - BT - A&A (Letter) LA - eng PY - 1997 EP - 17 T1 - 215 GHz VLBI observations of bright Active Galactic Nuclei T2 - A&A (Letter) TI - 215 GHz VLBI observations of bright Active Galactic Nuclei VL - 323 Y1 - 1997 ER - TY - JOUR A1 - A. Greve A1 - M. Torres A1 - J. E. Wink A1 - M. Grewing A1 - W. Wild A1 - J. Alcolea A1 - A. Barcia A1 - F. Colomer A1 - de P. Vincente A1 - J. Gomez-Gonzalez A1 - I. Lopez-Fernandez A1 - D. A. Graham A1 - T. P. Kirchbaum A1 - R. Schwartz A1 - K. J. Standke A1 - A. Witzel A1 - A. Baudry AU - BT - A&A (Letter) IS - L33 LA - eng PY - 1995 T1 - 215 GHz VLBI observations: Detection of fringes on the 1147 KM baseline Pico Veleta-Plateau de Bure T2 - A&A (Letter) TI - 215 GHz VLBI observations: Detection of fringes on the 1147 KM baseline Pico Veleta-Plateau de Bure VL - 299 Y1 - 1995 ER -