Explanipedia

A Possible Shutting-Down Event of Mass Accretion in An Active Galactic Nucleus at z~1.8 Open

Tomoki Morokuma, Malte Schramm, Toshihiro Kawaguchi, Josefa Becerra González, J. A. Acosta‐Pulido , et al. · 2025

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 ~20 years in the observed frame. This pronounced fading tr…

A possible shutting-down event of mass accretion in an active galactic nucleus at z ∼ 1.8 Open

Tomoki Morokuma, Malte Schramm, Toshihiro Kawaguchi, J. Becerra González, J. A. Acosta‐Pulido , et al. · 2025

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 ${\sim}20\!-\!30$ (in optical) over a period of ∼20 yr in the observed frame. This pronounce…

Radio Follow-up Observations of SN 2023ixf by Japanese and Korean Very Long Baseline Interferometers Open

Yuhei Iwata, Masanori Akimoto, Tomoki Matsuoka, Keiichi Maeda, Yoshinori Yonekura , et al. · 2025

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 interferometers (VLBIs), which are the Japanese VLBI Networ…

Radio Follow-up Observations of SN 2023ixf by Japanese and Korean VLBIs Open

Yuhei Iwata, Masanori Akimoto, Tomoki Matsuoka, Keiichi Maeda, Yoshinori Yonekura , et al. · 2024

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 interferometers (VLBIs), which are the Japanese VLBI Netwo…

The Japanese vision for the Black Hole Explorer mission Open

Kazunori Akiyama, Kotaro Niinuma, Kazuhiro Hada, Akihiro Doi, Yoshiaki Hagiwara , et al. · 2024

Akiyama, Kazunori et al.-- Full list of authors: Akiyama, Kazunori; Niinuma, Kotaro; Hada, Kazuhiro; Doi, Akihiro; Hagiwara, Yoshiaki; Higuchi, Aya E.; Honma, Mareki; Kawashima, Tomohisa; Kolev, Dimitar; Koyama, Shoko; Masui, Sho; Ohsuga, …

The Black Hole Explorer: motivation and vision Open

Michael D. Johnson, Kazunori Akiyama, Rebecca Baturin, Bryan Bilyeu, Lindy Blackburn , et al. · 2024

Johnson, Michael D. et al.-- Full list of authors: Johnson, Michael D.; Akiyama, Kazunori; Baturin, Rebecca; Bilyeu, Bryan; Blackburn, Lindy; Boroson, Don; Cárdenas-Avendaño, Alejandro; Chael, Andrew; Chan, Chi-kwan; Chang, Dominic; Cheime…

Black Hole Spacetime and Properties of Accretion Flows and Jets Probed by Black Hole Explorer: Science Cases Proposed by BHEX Japan Team Open

Tomohisa Kawashima, Yuh Tsunetoe, Ken Ohsuga, Motoki Kino, Yosuke Mizuno , et al. · 2024

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 and relativistic jets. We propose science cases anticipated…

The Black Hole Explorer: Motivation and Vision Open

Michael D. Johnson, Kazunori Akiyama, Rebecca Baturin, Bryan Bilyeu, Lindy Blackburn , et al. · 2024

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 (VLBI) to space. BHEX will discover and measure the bright …

Precessing jet nozzle connecting to a spinning black hole in M87 Open

Yuzhu Cui, Kazuhiro Hada, Tomohisa Kawashima, Motoki Kino, Weikang Lin , et al. · 2023

Spectral analysis of a parsec-scale jet in M 87: Observational constraint on the magnetic field strengths in the jet Open

Hyunwook Ro, Motoki Kino, Bong Won Sohn, Kazuhiro Hada, Jongho Park , et al. · 2023

Context. Because of its proximity and the large size of its black hole, M 87 is one of the best targets for studying the launching mechanism of active galactic nucleus jets. Currently, magnetic fields are considered to be an essential fact…

Very Long Baseline Interferometry imaging of H2O maser emission in the nearby radio galaxy NGC 4261 Open

Satoko Sawada‐Satoh, Nozomu Kawakatu, Kotaro Niinuma, Seiji Kameno · 2023

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 VLBI image of the 22 GHz H2O maser line and its location in t…

The Past and Future of East Asia to Italy: Nearly Global VLBI Open

G. Giovannini, Yuzhu Cui, Kazuhiro Hada, Kunwoo Yi, Hyunwook Ro , et al. · 2023

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, Japanese, and Italian researchers to study compact sources with …

Precessing jet nozzle connecting to a spinning black hole in M87 Open

Yuzhu Cui, Kazuhiro Hada, Tomohisa Kawashima, Motoki Kino, Weikang Lin , et al. · 2023

Powerful relativistic jets in active galactic nuclei (AGN) are believed to be originated from the accretion of material onto the supermassive black hole (SMBH) 1 . The nearby radio galaxy M87 is one of the best examples of this phenomenon,…

Spectral analysis of a parsec-scale jet in M87: Observational constraint on the magnetic field strengths in the jet Open

Hyunwook Ro, Motoki Kino, Bong Won Sohn, Kazuhiro Hada, Jongho Park , et al. · 2023

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, magnetic fields are considered to be an essential factor in the …

HINOTORI and Its Perspectives in the Black-Hole Jet Study Open

Toshihisa Tsutsumi, Kotaro Niinuma, Hiroshi Imai, Ryoko Amari, Yusuke Shimizu , et al. · 2023

Simultaneous multi-band very long baseline interferometry (VLBI) observations at millimeter wavelengths have huge potential for various science cases. However, there exist difficulties in expanding the scientific targets, as the sensitivit…

Recent updates of the Hitachi and Takahagi 32-m radio telescopes, Ibaraki Station Open

Yoshinori Yonekura, Yoshihiro Tanabe, Kenta Fujisawa, Kotaro Niinuma, Hideo Ogawa , et al. · 2023

ogy (NICT), have decided to use these antennas for JVN and East-Asian VLBI Network (EAVN).We will also use these antennas for single-dish and two-element interferometric observations.Conversion from telecommunication antennas to radio tele…

Development for Japan L-band VLBI Observation Open

Kohei Kurahara, Takuya Akahori, Kazuhiro Hada, Tomoya Hirota, Sota Ikebe , et al. · 2023

Activities of ngVLA-Japan Science Working Groups Open

Munetake Momose, Daisuke Iono, Akimasa Kataoka, Yoko Oya, Kengo Tachihara , et al. · 2023

The next generation Very Large Array (ngVLA) is an interferometric array planned by the National Radio Astronomical Observatory (NRAO).It will be operational in the late 2030s and improve the sensitivity and angular resolution of the curre…

Overview of the Observing System and Initial Scientific Accomplishments of the East Asian VLBI Network (EAVN) Open

Kazunori Akiyama, Juan Carlos Algaba, Tao An, Keiichi Asada, K. Asanok , et al. · 2022

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 Southeast Asian and European countries. EAVN currently consists o…

Detection of a bright burst from the repeating FRB 20201124A at 2 GHz Open

Sota Ikebe, Kazuhiro Takefuji, T. Terasawa, Sujin Eie, Takuya Akahori , et al. · 2022

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 Deep Space Center/JAXA. This is the first FRB observed by …

The Intrinsic Structure of Sagittarius A* at 1.3 cm and 7 mm Open

Ilje Cho, Guang-Yao Zhao, Tomohisa Kawashima, Motoki Kino, Kazunori Akiyama , et al. · 2022

Sagittarius A* (Sgr A*), the Galactic Center supermassive black hole (SMBH), is one of the best targets in which to resolve the innermost region of an SMBH with very long baseline interferometry (VLBI). In this study, we have carried out o…

A VLA Survey of Late-time Radio Emission from Superluminous Supernovae and the Host Galaxies Open

Bunyo Hatsukade, Nozomu Tominaga, Tomoki Morokuma, Kana Morokuma-Matsui, Yuichi Matsuda , et al. · 2021

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 5–21 yr after the explosions. The sample consists of 15 Type…

Morphological transition of the compact radio lobe in 3C84 via the strong jet-cloud collision Open

Motoki Kino, Kotaro Niinuma, Nozomu Kawakatu, Hiroshi Nagai, G. Giovannini , et al. · 2021

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 3C84 reveals that the hotspot in the radio lobe showed the …

East Asian VLBI Network observations of active galactic nuclei jets: imaging with KaVA+Tianma+Nanshan Open

Yu Zhu Cui, Kazuhiro Hada, Motoki Kino, Bong Won Sohn, Jongho Park , et al. · 2021

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, Japan, and Korea. EAVN aims at forming a joint VLBI Network b…

Morphological Transition of the Compact Radio Lobe in 3C 84 via the Strong Jet–Cloud Collision Open

Motoki Kino, Kotaro Niinuma, Nozomu Kawakatu, Hiroshi Nagai, G. Giovannini , et al. · 2021

We report multiepoch very long baseline interferometric observations of the compact radio lobe in the radio galaxy 3C 84 (NGC 1275) during 2016–2020. The image sequence of 3C 84 reveals that the hotspot in the radio lobe showed the 1 year …

A VLA Survey of Late-time Radio Emission from Superluminous Supernovae and the Host Galaxies Open

Bunyo Hatsukade, Nozomu Tominaga, Tomoki Morokuma, Kana Morokuma-Matsui, Yuichi Matsuda , et al. · 2021

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 5-21 years after the explosions. The sample consists of 15 T…

Variability of Late-time Radio Emission in the Superluminous Supernova PTF10hgi Open

Bunyo Hatsukade, Nozomu Tominaga, Tomoki Morokuma, Kana Morokuma-Matsui, Yoichi Tamura , et al. · 2021

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 observations at 8.6 and 10 yr after the explosion both detected r…

Millimeter-VLBI Detection and Imaging of the Gravitationally Lensed Gamma-Ray Blazar JVAS B0218+357 Open

Kazuhiro Hada, Kotaro Niinuma, J. Sitarek, Cristiana Spingola, Ayumi Hirano · 2020

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-ray source up to GeV/TeV energy bands, rendering a unique tar…

Millimeter-VLBI Detection and Imaging of the Gravitationally Lensed γ-Ray Blazar JVAS B0218+357 Open

Kazuhiro Hada, Kotaro Niinuma, J. Sitarek, Cristiana Spingola, Ayumi Hirano · 2020

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 γ -ray source up to GeV/TeV energy bands, rendering a unique target…

Stable Radio Core of the Blazar Mrk 501 during High-energy Active State in 2012 Open

Shoko Koyama, Motoki Kino, Akihiro Doi, Kotaro Niinuma, M. Giroletti , et al. · 2019

We investigate the precise location of the radio core in the nearby blazar Mrk 501 for the first time during its X-ray and TeV γ-ray active state in 2012 by revisiting from the perspective of astrometry the six-epoch observations with the …

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