Fumiya Imazato
A5057368273- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Mechanics and Biomechanics Studies
- Particle Detector Development and Performance
- Inertial Sensor and Navigation
- Medical Imaging Techniques and Applications
- Optical Systems and Laser Technology
- Radio Astronomy Observations and Technology
- Neutrino Physics Research
- Advanced X-ray and CT Imaging
- Adaptive optics and wavefront sensing
- Astronomy and Astrophysical Research
Hiroshima University
2018-2022
Abstract We present the Fermi Large Area Telescope (LAT) observations of binary neutron star merger event GW170817 and associated short gamma-ray burst (SGRB) GRB 170817A detected by Gamma-ray Burst Monitor. The LAT was entering South Atlantic Anomaly at time LIGO/Virgo trigger ( t GW ) therefore cannot place constraints on existence high-energy E > 100 MeV) emission with moment coalescence. focus instead constraining longer timescales. No candidate electromagnetic counterpart timescales...
Abstract We present optical observations of the Type Ia supernova (SN) 2019ein, starting two days after estimated explosion date. The spectra and light curves show that SN 2019ein belongs to a high-velocity (HV) broad-line group with relatively rapid decline in (Δ m 15 ( B ) = 1.36 ± 0.02 mag) short rise time (15.37 0.55 days). Si ii λ 6355 velocity, associated photospheric component but not detached feature, reached ∼20,000 km s −1 12 before -band maximum. line however, decreased very...
Abstract We analyzed Suzaku /XIS data (2006–2015) and Fermi /LAT (2008–2015) of the gamma-ray emitting radio galaxy NGC 1275. Correlated brightening nucleus in both X-ray GeV energy bands was found for period 2013–2015. This is first evidence correlated variability between these two also Swift /XRT that flux increased over several days 2010, coincidentally with flare. During flare, spectra were softer, a photon index ∼2 compared 1.5–2.1 other periods, suggesting synchrotron component. The...
Abstract The Laser Interferometer Gravitational-wave Observatory Scientific Collaboration and Virgo (LVC) sent out 56 gravitational-wave (GW) notices during the third observing run (O3). Japanese for Gravitational wave ElectroMagnetic follow-up (J-GEM) performed optical near-infrared observations to identify observe an electromagnetic (EM) counterpart. We constructed a web-based system that enabled us obtain share information on candidate host galaxies counterpart, status of our...
We report on the variations of physical parameters jet observed in blazar Mrk 421, and discuss origin X-ray flares jet, based analysis several spectral energy distributions (SEDs). The SEDs are modeled using one-zone synchrotron self-Compton (SSC) model its determined a Markov chain Monte Carlo method. lack data at TeV energies means many cannot be uniquely correlated. These studied detail. found that optimal solution can only when we apply constraint to one four parameters: magnetic field...
Abstract We present optical and near-infrared observations of SN 2019ehk, which was initially reported as a Type Ib supernova (SN). show that it evolved to Ca-rich transient according its spectral properties evolution in late phases. However, shows few distinct from those the canonical transients: short-duration first peak light curve, high luminosity, association with star-forming environment. Indeed, some these features are shared iPTF14gqr iPTF16hgs, candidates for special class...
XL-Calibur is a balloon-borne mission for hard x-ray polarimetry. The first launch currently scheduled from Sweden in summer 2022. Japanese collaborators provide telescope to the mission. telescope's design identical Hard X-ray Telescope (HXT, conically-approximated Wolter-I optics) on board ASTROH with same focal length of 12 m and aperture 45 cm, which can focus x-rays up 80 keV. divided into three segments circumferential direction, confocal 213 grazing-incidence mirrors are precisely...
This paper introduces a second-generation balloon-borne hard X-ray polarimetry mission, XL-Calibur. promises to give qualitatively new information about high-energy astrophysical sources, such as pulsars and binary black hole systems. The XL-Calibur contains grazing incidence telescope with focal plane detector unit that is sensitive linear polarization. very similar in design the ASTRO-H HXT telescopes has world's largest effective area above ~10 keV. combines low atomic number Compton...
Abstract We analyze the ultraviolet (UV) and X-ray data of NGC 1275 obtained with Swift/UV/Optical Telescope (UVOT), (XRT), Burst Alert (BAT) Fermi Large Area over about 10 yr to investigate origin nuclear emission from 1275. confirm that UV soft/hard fluxes gradually increased along GeV gamma rays. At times, short-term variations in or soft spectral regions showed rapid correlated However there was no significant correlation between X-rays. The spectrum had a narrow shape could be...
Since 2018 July, the black hole X-ray binary GRS 1915+105 has been in an low luminous state (XLLS), which is faintest period ever observed a soft band. We present here results of near-infrared (NIR) observations from 2019 April–December XLLS using HONIR attached to Kanata telescope, together with radio data obtained by Yamaguchi Interferometer and archival data. found historical NIR brightening XLLS. For several tens days XLLS, flux showed positive correlation negative flux. This result...