A5088348055- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Neutrino Physics Research
- Astrophysics and Star Formation Studies
- Nuclear physics research studies
- Atomic and Molecular Physics
- Adaptive optics and wavefront sensing
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Radio Astronomy Observations and Technology
- CCD and CMOS Imaging Sensors
- Planetary Science and Exploration
- Laser-Plasma Interactions and Diagnostics
- Nuclear Physics and Applications
- Magnetic confinement fusion research
- High-pressure geophysics and materials
- Spacecraft and Cryogenic Technologies
- Advanced Chemical Physics Studies
Tohoku University
1982-2025
Astronomical Institute of the Slovak Academy of Sciences
2025
Kanazawa University
2024
Kyoto University
1985-2023
RIKEN
2023
Nippon Soken (Japan)
2023
National Astronomical Observatory of Japan
2012-2022
The University of Tokyo
2009-2022
Kavli Institute for the Physics and Mathematics of the Universe
2011-2022
Konan University
2010-2021
Mergers of binary neutron stars (NSs) are among the most promising gravitational wave (GW) sources. Next generation GW detectors expected to detect signals from NS mergers within about 200 Mpc. The detection electromagnetic (EM) counterparts is crucial understanding nature Among possible EM emission merger, powered by radioactive r-process nuclei one best targets for follow-up observations. However, predictions so far have not taken into account detailed element abundances in ejecta. We...
Gravitational-wave observation together with a large number of electromagnetic observations shows that the source latest gravitational-wave event, GW170817, detected primarily by advanced LIGO, is merger binary neutron star. We attempt to interpret this observational event based on our results numerical-relativity simulations performed so far paying particular attention optical and infra-red observations. finally reach conclusion described consistently presence long-lived hypermassive or...
Coalescence of neutron stars gives rise to kilonova, thermal emission powered by radioactive decays freshly synthesized r-process nuclei. Although observational properties are largely affected bound-bound opacities elements, available atomic data have been limited. In this paper, we study element-to-element variation the in ejecta star mergers performing systematic structure calculations elements for first time. We show that distributions energy levels tend be higher as electron occupation...
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...
Abstract GRB 050709 was the first short Gamma-ray Burst (sGRB) with an identified optical counterpart. Here we report a reanalysis of publicly available data this event and discovery Li-Paczynski macronova/kilonova that dominates optical/infrared signal at t >2.5 days. Such would arise from 0.05 "Equation missing" r-process material launched by compact binary merger. The implied mass ejection supports suggestion mergers are significant possibly main sites heavy nucleosynthesis....
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...
The only supernovae (SNe) to show gamma-ray bursts (GRBs) or early x-ray emission thus far are overenergetic, broad-lined type Ic SNe (hypernovae, HNe). Recently, SN 2008D has shown several unusual features: (i) weak flash (XRF), (ii) an early, narrow optical peak, (iii) disappearance of the broad lines typical HNe, and (iv) development helium as in Ib. Detailed analysis shows that was not a normal supernova: Its explosion energy (E approximately 6x10(51) erg) ejected mass [ 7 times Sun...
Core-collapse supernovae (CC-SNe) are the explosions that announce death of massive stars. Some CC-SNe linked to long-duration gamma-ray bursts (GRBs) and highly aspherical. One important question is what extent asphericity common all CC-SNe. Here we present late-time spectra for a number from stripped-envelope stars use them explore any generated in inner part exploding star, near site collapse. A range oxygen emission-line profiles observed, including high incidence double-peaked profiles,...
Late-phase nebular spectra and photometry of Type Ib Supernova (SN) 2005bf taken by the Subaru telescope at ~270 ~310 days since explosion are presented. Emission lines ([O I] λλ6300, 6363; [Ca II] λλ7291, 7324; [Fe λ7155) show a blueshift ~1500-2000 km s-1. The [O doublet shows doubly peaked profile. line luminosities can be interpreted as coming from blob or jet containing only ~0.1-0.4 M☉, in which ~0.02-0.06 M☉ is 56Ni synthesized explosion. To explain blueshift, should either unipolar,...
Black hole-neutron star mergers are among the promising gravitational-wave sources for ground-based detectors, and gravitational waves from black expected to be detected in next few years. Simultaneous detection of electromagnetic counterparts with provides rich information about merger events. Among possible merger, emission powered by decay radioactive r-process nuclei, so called kilonova/macronova, is one best targets follow-up observation. We derive fitting formulas mass velocity ejecta...
We show model light curves of superluminous supernova 2006gy on the assumption that is powered by collision ejecta and its dense circumstellar medium. The initial conditions are constructed based shock breakout condition, assuming medium enough to cause within it. perform a set numerical curve calculations using one-dimensional multigroup radiation hydrodynamics code STELLA. succeeded in reproducing overall features early SN with whose mass about 15 Msun (the average mass-loss rate ~ 0.1...
Abstract Recent detection of gravitational waves from a neutron star (NS) merger event GW170817 and identification an electromagnetic counterpart provide unique opportunity to study the physical processes in NS mergers. To derive properties ejected material merger, we perform radiative transfer simulations kilonova, optical near-infrared emissions powered by radioactive decays r-process nuclei synthesized merger. We find that observed emission lasting for &gt;10 d is explained 0.03 M⊙...
Detection of the electromagnetic counterparts gravitational wave (GW) sources is important to unveil nature compact binary coalescences. We perform three-dimensional, time-dependent, multi-frequency radiative transfer simulations for radioactively powered emission from ejecta black hole (BH)–neutron star (NS) mergers. Depending on BH NS mass ratio, spin BH, and equations state dense matter, BH–NS mergers can eject more material than NS–NS In such cases, merger be luminous that show that, in...
We perform hydrodynamical calculations of core-collapse supernovae (SNe) with low explosion energies. These SNe do not have enough energy to eject the whole progenitor and most falls back central remnant. show that such fallback can a variety light curves (LCs) but their photospheric velocities only some limited values lower limits. also nucleosynthesis LCs several SN model, find from main-sequence mass 13 Msun account for properties peculiar Type Ia supernova 2008ha. The kinetic ejecta...
Abstract We report our identification of the optical afterglow and host galaxy short-duration gamma-ray burst sGRB 160821B. The spectroscopic redshift is z = 0.162, making it one lowest bursts (sGRBs) identified by Swift . Our intensive follow-up campaign using a range ground-based facilities as well Hubble Space Telescope , XMM-Newton shows evidence for late-time excess near-infrared emission in addition to complex afterglow. light curve at X-ray frequencies reveals narrow jet, <?CDATA...
An electromagnetic transient powered by the radioactive decay of r-process elements, a so-called kilonova/macronova, is one possible observable consequences compact binary mergers including at least neutron star. Recent observations strongly suggest discovery first transient, which associated with short gamma ray burst 130603B. We explore progenitor this event combining numerical-relativity simulations and radiative transfer dynamical ejecta star black hole–neutron mergers. show that models...
The next Galactic supernova is expected to bring great opportunities for the direct detection of gravitational waves (GW), full flavor neutrinos, and multi-wavelength photons. To maximize science return from such a rare event, it essential have established classes possible situations preparations appropriate observations. this end, we use long-term numerical simulation core-collapse (CCSN) 17 solar-mass red supergiant progenitor self-consistently model multi-messenger signals in GW,...
The kinetic energy of supernovae (SNe) accompanied by gamma-ray bursts (GRBs) tends to cluster near E52 erg, with 2.E52 erg an upper limit which no compelling exceptions are found (assuming a certain degree asphericity), and it is always significantly larger than the intrinsic GRB themselves (corrected for jet collimation). This strikingly similar maximum rotational neutron star rotating period 1 ms. It therefore proposed that all GRBs associated luminous SNe produced magnetars. result from...
Abstract Ejected material from neutron star mergers gives rise to electromagnetic emission powered by radioactive decays of r -process nuclei, the so-called kilonova or macronova. While properties are largely affected opacities in ejected material, available atomic data for elements still limited. We perform structure calculations elements: Se ( Z = 34), Ru 44), Te 52), Ba 56), Nd 60), and Er 68). confirm that bound–bound transitions open f -shell, lanthanide (Nd Er) higher than those other...
We present rapidly rising transients discovered by a high-cadence transient survey with Subaru telescope and Hyper Suprime-Cam. five at z=0.384-0.821 showing the rate faster than 1 mag per day in restframe near-ultraviolet wavelengths. The fast brightness are most similar to SN 2010aq PS1-13arp, for which ultraviolet emission within few days after shock breakout was detected. lower limit of event is ~9 % core-collapse supernova rates, assuming duration rapid rise be day. show that light...