284 citations · 606 across the 19 of their papers we have counts for
19 papers
Optical Super-orbital Modulation of SMC X-1: Disk Precession and a Revised Pulsar Mass
Masafumi Niwano, Nobuyuki Kawai, Michael Fausnaugh
The observational determination of the lower limit of neutron star masses is crucial for the physics of core-collapse supernovae. In this light, SMC X-1 is an important object beca…
Spectral and photometric variability of SS 433 observed with XRISM and simultaneous optical and near-infrared telescopes
Yusuke Sakai, Shinya Yamada, Yuta Okada +36
We present results from coordinated multiwavelength observations of the SS 433, obtained with XRISM, optical telescopes, and near-infrared camera during 2024 April and 2025 March.…
Multiband Optical Photometric and Spectroscopic Monitoring of the 2024 Flare Event in Transition Blazar OP313
TianFang Zhang, Mitsuru Kokubo, Mamoru Doi +19
Blazars are active galactic nuclei known for their extreme variability, offering unique opportunities to study jet physics and high-energy emission mechanisms. In 2024, the Flat Sp…
Optical Observations of the High Mass X-ray Binary MAXI J0709159/LY CMa
Megumi Shidatsu, Nobuyuki Kawai, Hiroyuki Maehara +12
We report on the optical spectroscopic monitoring of the X-ray transient MAXI J0709159 (identified as the Be star LY CMa) performed for about 1.5 months after the X-ray detectio…
UNIONS: The Ultraviolet Near-Infrared Optical Northern Survey
Stephen Gwyn, Alan W. McConnachie, Jean-Charles Cuillandre +86
The Ultraviolet Near-Infrared Optical Northern Survey (UNIONS) is a "collaboration of collaborations" that is using the Canada-France-Hawai'i Telescope, the Pan-STARRS telescopes,…
The possible long-term periodic variability of the extremely luminous quasar WISE J090924.01+000211.1
Takashi Horiuchi, Yoshiki Toba, Toru Misawa +11
The extremely luminous infrared galaxy (ELIRG), WISE J090924.01+000211.1 (hereafter; WISE J0909+0002, ) is an extraordinary object with a quasar aspect. This study performs…
Evolution of Accretion Disk Structure of the Black Hole X-ray Binary MAXI J1820070 during the Rebrightening Phase
Tomohiro Yoshitake, Megumi Shidatsu, Yoshihiro Ueda +18
To understand the evolution of global accretion disk structure in the ``rebrightening'' phase of MAXI J1820070, we perform a comprehensive analysis of its near infrared/optical/…
Multiwavelength Observations of the Black Hole X-ray Binary MAXI J1820070 in the Rebrightening Phase
Tomohiro Yoshitake, Megumi Shidatsu, Yoshihiro Ueda +14
We report the results of quasi-simultaneous multiwavelength (near-infrared, optical, UV, and X-ray) observations of the Galactic X-ray black hole binary MAXI J1820+070 performed in…
Possible anti-correlations between pulsation amplitudes and the disk growth of Be stars in giant-outbursting Be X-ray binaries
Masafumi Niwano, Michael M. Fausnaugh, Ryan M. Lau +15
The mechanism of X-ray outbursts in Be X-ray binaries remains a mystery, and understanding their circumstellar disks is crucial for a solution of the mass-transfer problem. In part…
MASTER OT J030227.28+191754.5: an unprecedentedly energetic dwarf nova outburst
Yusuke Tampo, Taichi Kato, Keisuke Isogai +60
We present a detailed study of the MASTER OT J030227.28+191754.5 outburst in 2021-2022, reaching an amplitude of 10.2 mag and a duration of 60 d. The detections of (1) the double-p…
Optical and X-ray variations during 5 outbursts of Aql X-1 in 3.6 years from 2016
Masafumi Niwano, Katsuhiro L. Murata, Naohiro Ito +2
We analyzed optical/X-ray quasi-simultaneous light curves of Aql X-1, obtained by MAXI (Monitor of All-sky X-ray Image), ZTF (Zwicky Transient Facility) and LCO (Las Cumbres Observ…
Multicolor and multi-spot observations of Starlink's Visorsat
Takashi Horiuchi, Hidekazu Hanayama, Masatoshi Ohishi +25
This study provides the results of simultaneous multicolor observations for the first Visorsat (STARLINK-1436) and the ordinary Starlink satellite, STARLINK-1113 in the , , $…
A nearby long gamma-ray burst from a merger of compact objects
E. Troja, C. L. Fryer, B. O'Connor +21
Gamma-ray bursts (GRBs) are flashes of high-energy radiation arising from energetic cosmic explosions. Bursts of long (>2 s) duration are produced by the core-collapse of massive s…
Discovery of a Long-Duration Superflare on a Young Solar-Type Star EK Draconis with Nearly Similar Time Evolution for H and White-Light Emissions
Kosuke Namekata, Hiroyuki Maehara, Satoshi Honda +17
Young solar-type stars are known to show frequent "superflares", which may severely influence the habitable worlds on young planets via intense radiations and coronal mass ejection…
Probable detection of an eruptive filament from a superflare on a solar-type star
Kosuke Namekata, Hiroyuki Maehara, Satoshi Honda +20
Solar flares are often accompanied by filament/prominence eruptions ( K and cm), sometimes leading to coronal mass ejections (CMEs) that direct…
J-GEM optical and near-infrared follow-up of gravitational wave events during LIGO's and Virgo's third observing run
Mahito Sasada, Yousuke Utsumi, Ryosuke Itoh +68
The Laser Interferometer Gravitational-wave Observatory Scientific Collaboration and Virgo Collaboration (LVC) sent out 56 gravitational-wave (GW) notices during the third observin…
GPU-accelerated Image Reduction Pipeline
Masafumi Niwano, Katsuhiro L. Murata, Ryo Adachi +6
We developed a high-speed image reduction pipeline using Graphics Processing Units (GPUs) as hardware accelerators. Astronomers desire detecting EM counterpart of gravitational-wav…
Optical and X-ray observations of stellar flares on an active M dwarf AD Leonis with Seimei Telescope, SCAT, NICER and OISTER
Kosuke Namekata, Hiroyuki Maehara, Ryo Sasaki +24
We report multi-wavelength monitoring observations of an M-dwarf flare star AD Leonis with Seimei Telescope (6150--7930 Å), SCAT (Spectroscopic Chuo-university Astronomical Telesco…
Type Ia SN 2019ein: New Insights into the Similarities and diversities among High-Velocity SNe Ia
Miho Kawabata, Keiichi Maeda, Masayuki Yamanaka +38
We present optical observations of type Ia supernova (SN) 2019ein, starting at 2 days after the estimated explosion date. The spectra and the light curves show that SN 2019ein belo…