Katsuhiro L. Murata
A5078782186- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- Astrophysics and Cosmic Phenomena
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- High-pressure geophysics and materials
- SAS software applications and methods
- Scientific Research and Discoveries
- Magnetic confinement fusion research
- Planetary Science and Exploration
- Particle accelerators and beam dynamics
- CCD and CMOS Imaging Sensors
- Paleopathology and ancient diseases
- Radio Astronomy Observations and Technology
- Laser-Plasma Interactions and Diagnostics
- Statistical and numerical algorithms
- Mechanics and Biomechanics Studies
- Inorganic Fluorides and Related Compounds
Tokyo Institute of Technology
2017-2024
Okayama University
2023-2024
Kyoto University
2023-2024
Nagoya University
2010-2019
Ehime University
2014
The first detected gravitational wave from a neutron star merger was GW170817. In this study, we present J-GEM follow-up observations of SSS17a, an electromagnetic counterpart SSS17a shows 2.5-mag decline in the $z$-band 1.7 days to 7.7 after merger. Such rapid is not comparable with supernovae light curves at any epoch. color also evolves rapidly and becomes redder for later epochs; $z-H$ changed by approximately 2.5 mag period 0.7 days. evolution both optical brightness are consistent...
Wide-field optical surveys have begun to uncover large samples of fast (trise ≲ 5 d), luminous (Mpeak < −18), blue transients. While commonly attributed the breakout a supernova shock into dense wind, great distances transients this class found so far hampered detailed investigation their properties. We present photometry and spectroscopy from comprehensive worldwide campaign observe AT 2018cow (ATLAS 18qqn), first fast-luminous transient be in real time at low redshift. Our spectra (<2 days...
Gamma-ray bursts (GRBs) are flashes of high-energy radiation arising from energetic cosmic explosions. Bursts long (>2 s) duration produced by the core-collapse massive stars, those short (< 2 merger two neutron stars (NSs). A third class events with hybrid properties was identified, but never conclusively linked to a stellar progenitor. The lack bright supernovae rules out typical explosions, their distance scales prevent sensitive searches for direct signatures progenitor system. Only...
Solar flares are often accompanied by filament/prominence eruptions ($\sim10^{4}$ K and $\sim 10^{10-11}$ cm$^{-3}$), sometimes leading to coronal mass ejections (CMEs) that directly affect the Earth's environment. `Superflares' found on some active solar-type (G-type main-sequence) stars, but association of filament eruptions/CMEs has not been established. Here we show our optical spectroscopic observation young star EK Draconis reveals evidence for a stellar eruption associated with...
Abstract We report results from the X-ray and optical monitoring of black hole candidate MAXI J1820+070 (=ASSASN-18ey) over entire period its outburst 2018 March to October. In this outburst, source exhibited two sets “fast rise slow decay”-type long-term flux variations. found that 1–100 keV luminosities at peaks were almost same, although a significant spectral softening was only seen in second rise. This confirms state transition low/hard high/soft is not determined by mass accretion rate...
In this paper, we present the results from spectroscopic and photometric observations of M-type flare star YZ CMi in framework Optical Infrared Synergetic Telescopes for Education Research (OISTER) collaborations during Transiting Exoplanet Survey Satellite (TESS) observation period. We detected 145 white-light flares TESS light curve 4 H$\alpha$ OISTER performed between 2019-01-16 2019-01-18. Among them, 3 were associated with flares. However, one them did not show clear brightening...
The relation between the ratio of infrared (IR) and ultraviolet (UV) flux densities (the excess: IRX) slope UV spectrum (β) galaxies plays a fundamental role in evaluation dust attenuation star-forming galaxies, especially at high redshifts. Many authors, however, have pointed out that there is significant dispersion and/or deviation from originally proposed IRX–β depending on sample selection. We reexamined by measuring far- near-UV original with GALEX AKARI imaging data constructed revised...
We report multi-wavelength monitoring observations of an M-dwarf flare star AD Leonis with Seimei Telescope (6150--7930 {\AA}), SCAT (Spectroscopic Chuo-university Astronomical Telescope; 3700--7500 NICER (Neutron Star Interior Composition Explorer; 0.2--12.0 keV), and collaborations OISTER (Optical Infrared Synergetic Telescopes for Education Research) program. Twelve flares are detected in total which include ten H$\alpha$, four X-ray, optical-continuum flares; one them is a superflare the...
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 ejections. Here we report an optical spectroscopic photometric observation of a long-duration superflare star EK Draconis (50-120 Myr age) with Seimei telescope $Transiting$ $Exoplanet$ $Survey$ $Satellite$ ($TESS$). The flare energy 2.6$\times$10$^{34}$ erg white-light duration 2.2 hr much larger than those largest solar...
<i>Aims. <i/>We explore spectral energy distributions (SEDs), star formation (SF), and dust extinction properties of galaxies in the Local Universe.<i>Methods. <i/>The AKARI all-sky survey provided first bright point source catalog detected at 90 <i>μ<i/>m. Beginning with this catalog, we selected by matching sources those IRAS redshift survey. We measured total GALEX FUV NUV flux densities a photometry software specifically developed for purpose. In further step matched sample Sloan digital...
Using the Hubble Space Telescope/Advanced Camera for Surveys data in COSMOS field, we systematically searched clumpy galaxies at 0.2 < z 1.0 and investigated fraction of its evolution as a function stellar mass, star formation rate (SFR), specific SFR (SSFR). The star-forming with Mstar > 109.5 M☉ decreases time from ∼0.35 0.8 to ∼0.05 0.4, irrespective although tends be slightly lower massive 1010.5 each redshift. On other hand, increases increasing both SSFR all redshift ranges...
ABSTRACT We investigate morphological properties of 61 Ly α emitters (LAEs) at z = 4.86 identified in the COSMOS field, based on Hubble Space Telescope Advanced Camera for Surveys (ACS) imaging data F814W band. Out LAEs, we find ACS counterparts 54 LAEs. Eight LAEs show double-component structures with a mean projected separation 0.″63 (∼4.0 kpc 4.86). Considering faintness these sources, carefully evaluate their properties, that is, size and ellipticity. While some them are compact...
We present our optical follow-up observations to search for an electromagnetic counterpart of the first gravitational wave source GW150914 in framework Japanese collaboration Gravitational ElectroMagnetic (J-GEM), which is observing group utilizing and radio telescopes Japan, as well those New Zealand, China, South Africa, Chile, Hawaii. carried out a wide-field imaging survey with Kiso Wide Field Camera (KWFC) on 1.05-m Schmidt telescope Japan galaxy-targeted Tripole5 B&C 61-cm Zealand....
Abstract We present visible and near-infrared (NIR) photometric spectroscopic observations of interstellar object (ISO) 2I/Borisov taken from 2019 September 10 to December 20 using the GROWTH, Apache Point Observatory Astrophysical Research Consortium 3.5 m, NASA Infrared Telescope Facility 3.0 m combined with pre- postdiscovery 2I obtained by Zwicky Transient March 17 May 5. Comparison imaging distant solar system comets shows an very similar mildly active outgassing rate ∼10 27 mol s −1 ....
Abstract We report the analysis of additional multiband photometry and spectroscopy new adaptive optics (AO) imaging nearby planetary microlensing event TCP J05074264+2447555 (Kojima-1), which was discovered toward Galactic anticenter in 2017 (Nucita et al.). confirm nature light-curve anomaly around peak while finding no feature this event. also presence apparent blending flux absence significant parallax signal reported literature. The AO image reveals contaminating sources, making it most...
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...
We present results of optical polarimetric and multi-band photometric observations for gamma-ray loud narrow-line Seyfert 1 galaxy 1H 0323+342. This object has been monitored by 1.5 m Kanata telescope since 2012 September but following a flux enhancement detected Fermi-LAT on MJD 56483 (2013 July 10) dense follow-up was performed ten 0.5-2.0 telescopes in Japan over one week. The 2-year R_C-band light curve showed clear brightening corresponding to the increase then decayed gradually. high...
We present simultaneous optical and near-infrared (NIR) polarimetric results for the black hole binary V404 Cygni spanning duration of its 7-day long optically-brightest phase 2015 June outburst. The R Ks-band light curves showed almost same temporal variation except isolated (~30 min duration) orphan flare observed at MJD 57193.54. did not find any significant polarization degree (PD) position angle (PA) in both Ks bands throughout our observations, including NIR flare. show that PD PA are...
We present the early-phase spectra and light curves of broad-lined supernova (SN) 2016coi from $t=7$ to $67$ days after estimated explosion date. This SN was initially reported as a Type Ic (SN Ic-BL). However, we found that up $t=12$ exhibited He~{\sc i} $\lambda$5876, $\lambda$6678, $\lambda$7065 absorption lines. show smoothed blueshifted normal SNe Ib are remarkably similar observed spectrum 2016coi. The line velocities were those Ic-BL significantly faster than Ib. Analyses velocity...
Abstract We report the results of optical–infrared follow-up observations gravitational wave (GW) event GW151226 detected by Advanced LIGO in framework J-GEM (Japanese collaboration for Gravitational ElectroMagnetic follow-up). performed wide-field optical imaging surveys with Kiso Wide Field Camera (KWFC), Hyper Suprime-Cam (HSC), and MOA-cam3. The KWFC survey started at 2.26 d after GW covered 778 deg2 centered high Galactic region skymap GW151226. HSC from ∼12 an area 63.5 highest...
We present comprehensive spectroscopic and photometric analyses of the intermediate luminosity Type Iax supernova (SN Iax) 2019muj based on multi-band datasets observed through framework OISTER target-of-opportunity program. SN exhibits almost identical characteristics with subluminous SNe 2008ha 2010ae in terms spectral features light curve evolution at early phase, except for peak luminosity. The long-term observations unveil flattening curves late time as seen a luminous 2014dt. This can...
Abstract We report X-ray, optical, and near-infrared monitoring of the new X-ray transient MAXI J1820+070 discovered with on 2018 March 11. Its intensity reached ∼2 crab at 2–20 keV end March, then gradually decreased until middle June. In this period, spectrum was described by Comptonization disk emission, a photon index ∼1.5 an electron temperature ∼50 keV, which is consistent black hole binary in low/hard state. The slightly decreased, increased, increasing flux. source showed significant...
We report a new observation of the Jupiter-family comet 209P/LINEAR during its 2014 return. The is recognized as dust source meteor shower, May Camelopardalids. was apparently inactive at heliocentric distance rh = 1.6 au and showed weak activity < 1.4 au. found an active region <0.001% entire nuclear surface comet's dormant phase. An edge-on image suggests that particles up to 1 cm in size (with uncertainty factor 3-5) were ejected following differential power-law distribution with index...