Publications

2014
K. Hada, M. Giroletti, M. Kino, G. Giovannini, F. D'Ammando, C. C. Cheung, M. Beilicke, H. Nagai, A. Doi, K. Akiyama, M. Honma, K. Niinuma, C. Casadio, M. Orienti, H. Krawczynski, J. L. Gómez, S. Sawada-Satoh, S. Koyama, A. Cesarini, S. Nakahara, and M. A. Gurwell. 2014. “A Strong Radio Brightening at the Jet Base of M 87 during the Elevated Very High Energy Gamma-Ray State in 2012.” ApJ, 788, Pp. 165.
M. Honma, K. Akiyama, M. Uemura, and S. Ikeda. 2014. “Super-resolution imaging with radio interferometry using sparse modeling.” PASJ, 66, Pp. 95.
K. Niinuma, S.-S. Lee, M. Kino, B. W. Sohn, K. Akiyama, G.-Y. Zhao, S. Sawada-Satoh, S. Trippe, K. Hada, T. Jung, Y. Hagiwara, R. Dodson, S. Koyama, M. Honma, H. Nagai, A. Chung, A. Doi, K. Fujisawa, M.-H. Han, J.-S. Kim, J. Lee, J. A. Lee, A. Miyazaki, T. Oyama, K. Sorai, K. Wajima, J. Bae, D.-Y. Byun, S.-H. Cho, Y. K. Choi, H. Chung, M.-H. Chung, S.-T. Han, T. Hirota, J.-W. Hwang, D.-H. Je, T. Jike, D.-K. Jung, J.-S. Jung, J.-H. Kang, J. Kang, Y.-W. Kang, Y. Kan-ya, M. Kanaguchi, N. Kawaguchi, B. G. Kim, H. R. Kim, H.-G. Kim, J. Kim, J. Kim, K.-T. Kim, M. Kim, H. Kobayashi, Y. Kono, T. Kurayama, C. Lee, J.-W. Lee, S. H. Lee, Y. C. Minh, N. Matsumoto, A. Nakagawa, C. S. Oh, S.-J. Oh, S.-Y. Park, D.-G. Roh, T. Sasao, K. M. Shibata, M.-G. Song, Y. Tamura, S.-O. Wi, J.-H. Yeom, and Y. J. Yun. 2014. “VLBI observations of bright AGN jets with the KVN and VERA Array (KaVA): Evaluation of imaging capability.” PASJ, 66, Pp. 103.
2013
K. Hada, A. Doi, H. Nagai, M. Inoue, M. Honma, M. Giroletti, and G. Giovannini. 2013. “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).” ApJ, 779, Pp. 6.
R.-S. Lu, V. L. Fish, K. Akiyama, S. S. Doeleman, J. C. Algaba, G. C. Bower, C. Brinkerink, R. Chamberlin, G. Crew, R. J. Cappallo, M. Dexter, R. Freund, P. Friberg, M. A. Gurwell, P. T. P. Ho, M. Honma, M. Inoue, S. G. Jorstad, T. P. Krichbaum, L. Loinard, D. MacMahon, D. P. Marrone, A. P. Marscher, J. M. Moran, R. Plambeck, N. Pradel, R. Primiani, R. P. J. Tilanus, M. Titus, J. Weintroub, M. Wright, K. H. Young, and L. M. Ziurys. 2013. “Fine-scale Structure of the Quasar 3C 279 Measured with 1.3 mm Very Long Baseline Interferometry.” ApJ, 772, Pp. 13.
H. Nagai, M. Kino, K. Niinuma, K. Akiyama, K. Hada, S. Koyama, M. Orienti, K. Hiura, S. Sawada-Satoh, M. Honma, G. Giovannini, M. Giroletti, K. Shibata, and K. Sorai. 2013. “The GENJI Programme: Gamma-Ray Emitting Notable AGN Monitoring by Japanese VLBI.” PASJ, 65, Pp. 24.
K. Hada, M. Kino, A. Doi, H. Nagai, M. Honma, Y. Hagiwara, M. Giroletti, G. Giovannini, and N. Kawaguchi. 2013. “The Innermost Collimation Structure of the M87 Jet Down to \~10 Schwarzschild Radii.” ApJ, 775, Pp. 70.
K. Akiyama, R. Takahashi, M. Honma, T. Oyama, and H. Kobayashi. 2013. “Multi-Epoch VERA Observations of Sagittarius A*. I. Images and Structural Variability.” PASJ, 65, Pp. 91.
A. Doi, Y. Murata, N. Mochizuki, H. Takeuchi, K. Asada, T. J. Hayashi, H. Nagai, K. M. Shibata, T. Oyama, T. Jike, K. Fujisawa, K. Sugiyama, H. Ogawa, K. Kimura, M. Honma, H. Kobayashi, and S. Koyama. 2013. “Multifrequency VLBI Observations of the Broad Absorption Line Quasar J1020+4320: Recently Restarted Jet Activity?.” PASJ, 65, Pp. 57.
M. Nakamura and K. Asada. 2013. “The Parabolic Jet Structure in M87 as a Magnetohydrodynamic Nozzle.” ApJ, 775, Pp. 118.Abstract
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.
2012
M. Giroletti, K. Hada, G. Giovannini, C. Casadio, M. Beilicke, A. Cesarini, C. C. Cheung, A. Doi, H. Krawczynski, M. Kino, N. P. Lee, and H. Nagai. 2012. “The kinematic of HST-1 in the jet of M 87.” A&A, 538, Pp. L10.
K. Hada, M. Kino, H. Nagai, A. Doi, Y. Hagiwara, M. Honma, M. Giroletti, G. Giovannini, and N. Kawaguchi. 2012. “VLBI Observations of the Jet in M 87 during the Very High Energy γ-Ray Flare in 2010 April.” ApJ, 760, Pp. 52.
2011
K. Hada, A. Doi, M. Kino, H. Nagai, Y. Hagiwara, and N. Kawaguchi. 2011. “An origin of the radio jet in M87 at the location of the central black hole.” Nature, 477, Pp. 185-187.

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