166 citations · 1.3k across the 60 of their papers we have counts for
62 papers
Resolving Nearby Supermassive Black Holes with the Black Hole Explorer
Yuto Akiyama, Kazunori Akiyama, Dominic W. Pesce +12
Recent Event Horizon Telescope results have demonstrated unique and transformative science in gravitational physics and black hole astrophysics enabled by event-horizon-scale imagi…
Radio Constraints on the Circumstellar Environment of the Type IIb Supernova SN 2024iss
Yuhei Iwata, Tomoki Matsuoka, Masanori Akimoto +6
Type~IIb supernovae exhibit diverse progenitor properties, and radio observations offer a unique probe of their mass-loss histories shortly before the explosion. We present Japanes…
Black Hole Explorer Mission Development in Japan
Kazunori Akiyama, Mareki Honma, Akihiro Doi +21
The Black Hole Explorer (BHEX) is a next-generation space very-long-baseline interferometry (VLBI) mission concept that will extend existing ground-based millimeter/submillimeter V…
VLBI Astrometry of Magnetars
Takuya Akahori, Sujin Eie, Kei Amada +8
The origin of the strongest magnetic fields in the Universe, i.e., the origin of magnetars, is a longstanding question. An enhanced dynamo effect in an irregular supernova explosio…
VLBI-Enabled Localization of Continuous GW Sources
Keitaro Takahashi, Takuya Akahori, Kenta Fujisawa +8
Pulsar timing arrays (PTAs) are opening the nanohertz gravitational-wave (GW) band by timing millisecond pulsars (MSPs) to target signals from supermassive black hole binaries (SMB…
Fast variability and circular polarization of the 6.7 GHz methanol maser in G33.6410.228
Kenta Fujisawa, Yui Sugiura, Yuta Kojima +5
The 6.7 GHz methanol maser in a high-mass star-forming region G33.6410.228 is known to exhibit burst-like flux variability due to an unknown mechanism. To investigate the burst…
A Possible Shutting-Down Event of Mass Accretion in An Active Galactic Nucleus at z~1.8
Tomoki Morokuma, Malte Schramm, Toshihiro Kawaguchi +11
We present the discovery of a large gradual apparent fading event in optical and near-infrared wavelengths in a quasar at z=1.767 by a factor of 20-30 (in optical) over a period of…
Radio Follow-up Observations of SN 2023ixf by Japanese and Korean VLBIs
Yuhei Iwata, Masanori Akimoto, Tomoki Matsuoka +10
We report on radio follow-up observations of the nearby Type II supernova, SN 2023ixf, spanning from 1.7 to 269.9 days after the explosion, conducted using three very long baseline…
Black Hole Spacetime and Properties of Accretion Flows and Jets Probed by Black Hole Explorer: Science Cases Proposed by BHEX Japan Team
Tomohisa Kawashima, Yuh Tsunetoe, Ken Ohsuga +7
Black Hole Explorer (BHEX) is a space VLBI mission concept, which can probe the black hole spacetime and the plasma properties including the magnetic fields of the accretion flows…
The Black Hole Explorer: Motivation and Vision
Michael D. Johnson, Kazunori Akiyama, Rebecca Baturin +65
We present the Black Hole Explorer (BHEX), a mission that will produce the sharpest images in the history of astronomy by extending submillimeter Very-Long-Baseline Interferometry…
The Japanese Vision for the Black Hole Explorer Mission
Kazunori Akiyama, Kotaro Niinuma, Kazuhiro Hada +43
The Black Hole Explorer (BHEX) is a next-generation space very long baseline interferometry (VLBI) mission concept that will extend the ground-based millimeter/submillimeter arrays…
Crystal structures and superconducting properties of metallic double-chain based cuprate Pr2Ba4Cu7O15-delta
Masahide Hagawa, Michiaki Matsukawa, Kota Niinuma +7
We demonstrated the lattice structures and the superconducting phases of metallic double-chain based cuprate Pr2Ba4Cu7O15-delta exhibiting higher Tc. After the oxygen heat treatmen…
Precessing jet nozzle connecting to a spinning black hole in M87
Yuzhu Cui, Kazuhiro Hada, Tomohisa Kawashima +76
The nearby radio galaxy M87 offers a unique opportunity to explore the connections between the central supermassive black hole and relativistic jets. Previous studies of the inner…
Very Long Baseline Interferometry imaging of H2O maser emission in the nearby radio galaxy NGC 4261
Satoko Sawada-Satoh, Nozomu Kawakatu, Kotaro Niinuma +1
We report dual-frequency very long baseline interferometry (VLBI) observations at 22 and 43 GHz toward the nucleus of a nearby radio galaxy NGC 4261. In particular, we present a VL…
The Past and Future of East Asia to Italy: Nearly Global VLBI
Gabriele Giovannini, Yuzhu Cui, Kazuhiro Hada +29
We present here the East Asia to Italy Nearly Global VLBI (EATING VLBI) project. How this project started and the evolution of the international collaboration between Korean, Japan…
Spectral analysis of a parsec-scale jet in M87: Observational constraint on the magnetic field strengths in the jet
Hyunwook Ro, Motoki Kino, Bong Won Sohn +49
Because of its proximity and the large size of its black hole, M87 is one of the best targets for studying the launching mechanism of active galactic nucleus jets. Currently, magne…
Overview of the Observing System and Initial Scientific Accomplishments of the East Asian VLBI Network (EAVN)
Kazunori Akiyama, Juan-Carlos Algaba, Tao An +101
The East Asian VLBI Network (EAVN) is an international VLBI facility in East Asia and is operated under mutual collaboration between East Asian countries, as well as part of Southe…
Detection of a bright burst from the repeating FRB 20201124A at 2 GHz
Sota Ikebe, Kazuhiro Takefuji, Toshio Terasawa +14
We present a detection of a bright burst from FRB 20201124A, which is one of the most active repeating FRBs, based on S-band observations with the 64-m radio telescope at the Usuda…
The intrinsic structure of Sagittarius A* at 1.3 cm and 7 mm
Ilje Cho, Guang-Yao Zhao, Tomohisa Kawashima +63
Sagittarius A* (Sgr A*), the Galactic Center supermassive black hole (SMBH), is one of the best targets to resolve the innermost region of SMBH with very long baseline interferomet…
Morphological transition of the compact radio lobe in 3C84 via the strong jet-cloud collision
Motoki Kino, Kotaro Niinuma, Nozomu Kawakatu +8
We report multi-epoch Very Long Baseline Interferometric (VLBI) observations of the compact radio lobe in the radio galaxy 3C84 (NGC1275) during 2016 - 2020. The image sequence of…
A VLA Survey of Late-time Radio Emission from Superluminous Supernovae and the Host Galaxies
Bunyo Hatsukade, Nozomu Tominaga, Tomoki Morokuma +5
We present the results of 3 GHz radio continuum observations of 23 superluminous supernovae (SLSNe) and their host galaxies by using the Karl G. Jansky Very Large Array conducted 5…
East Asian VLBI Network Observations of Active Galactic Nuclei Jets: Imaging with KaVA+Tianma+Nanshan
Yuzhu Cui, Kazuhiro Hada, Motoki Kino +74
The East Asian very-long-baseline interferometry (VLBI) Network (EAVN) is a rapidly evolving international VLBI array that is currently promoted under joint efforts among China, Ja…
Variability of Late-time Radio Emission in SLSN PTF10hgi
Bunyo Hatsukade, Nozomu Tominaga, Tomoki Morokuma +6
We report the time variability of the late-time radio emission in a Type-I superluminous supernova (SLSN), PTF10hgi, at z = 0.0987. The Karl G. Jansky Very Large Array 3 GHz observ…
Millimeter-VLBI Detection and Imaging of the Gravitationally Lensed Gamma-Ray Blazar JVAS B0218+357
Kazuhiro Hada, Kotaro Niinuma, Julian Sitarek +2
We observed the gravitationally lensed blazar JVAS B0218+357 with the KVN and VERA Array (KaVA) at 22, 43, and 86 GHz. The source has recently been identified as an active gamma-ra…