148 citations · 1.6k across the 38 of their papers we have counts for
38 papers
Inhomogeneous stellar mixing in the final hours before the Cassiopeia A supernova
Toshiki Sato, Kai Matsunaga, Hiroyuki Uchida +10
Understanding stars and their evolution is a key goal of astronomical research and has long been a focus of human interest. In recent years, theorists have paid much attention to t…
EMPRESS. XIII. Chemical Enrichments of Young Galaxies Near and Far at z ~ 0 and 4-10: Fe/O, Ar/O, S/O, and N/O Measurements with Chemical Evolution Model Comparisons
Kuria Watanabe, Masami Ouchi, Kimihiko Nakajima +14
We present gas-phase elemental abundance ratios of 7 local extremely metal-poor galaxies (EMPGs) including our new Keck/LRIS spectroscopy determinations together with 33 JWST $z\si…
Monotonicity of the cores of massive stars
Koh Takahashi, Tomoya Takiwaki, Takashi Yoshida
Massive stars are linked with diverse astronomical processes and objects including star formation, supernovae and their remnants, cosmic rays, interstellar media, and galaxy evolut…
Evolution and explosions of metal enriched supermassive stars: proton rich general relativistic instability supernovae
Chris Nagele, Hideyuki Umeda, Koh Takahashi
The assembly of supermassive black holes poses a challenge primarily because of observed quasars at high redshift, but additionally because of the current lack of observations of i…
Pulsations of primordial supermassive stars induced by a general relativistic instability; visible to JWST at z12
Chris Nagele, Hideyuki Umeda, Koh Takahashi +1
The origin of high-redshift quasars and their supermassive black hole engines is unclear. One promising solution is the collapse of a primordial supermassive star. Observational co…
Stability analysis of supermassive primordial stars: a new mass range for general relativistic instability supernovae
Chris Nagele, Hideyuki Umeda, Koh Takahashi +2
Observed supermassive black holes in the early universe have several proposed formation channels, in part because most of these channels are difficult to probe. One of the more pro…
Stellar models of Betelgeuse constrained using observed surface conditions
Tianyin Luo, Hideyuki Umeda, Takashi Yoshida +1
We study stellar models for Betelgeuse using the HR diagram and surface abundances as observational constraints. Previous studies on Betelgeuse have not systematically investigated…
Neutrino emission from the collapse of population III supermassive stars
Chris Nagele, Hideyuki Umeda, Koh Takahashi +2
We calculate the neutrino signal from Population III supermassive star collapse using a neutrino transfer code originally developed for core collapse supernovae and massive star co…
A three-dimensional hydrodynamics simulation of oxygen-shell burning in the final evolution of a fast-rotating massive star
Takashi Yoshida, Tomoya Takiwaki, David R. Aguilera-Dena +5
We perform for the first time a 3D hydrodynamics simulation of the evolution of the last minutes pre-collapse of the oxygen shell of a fast-rotating massive star. This star has an…
Ultra-delayed neutrino-driven explosion of rotating massive-star collapse
Sho Fujibayashi, Koh Takahashi, Yuichiro Sekiguchi +1
Long-term neutrino-radiation hydrodynamics simulations in full general relativity are performed for the collapse of rotating massive stars that are evolved from He-stars with their…
Impact of binary interactions on the diffuse supernova neutrino background
Shunsaku Horiuchi, Tomoya Kinugawa, Tomoya Takiwaki +2
Binary interactions, especially mass transfer and mergers, can strongly influence the evolution of massive stars and change their final properties and the occurrence of supernovae.…
Three-dimensional Hydrodynamics Simulations of Precollapse Shell Burning in the Si- and O-rich Layers
Takashi Yoshida, Tomoya Takiwaki, Kei Kotake +3
We present 3D hydrodynamics simulations of shell burning in two progenitors with zero-age main-sequence masses of 22 and 27 for 65 and 200 s up to the onset of gr…
Pulsational pair-instability and the mass gap of Population III Black Holes: Effects of overshooting
Hideyuki Umeda, Takashi Yoshida, Chris Nagele +1
Since the discovery of GW190521, several proposals have been put forward to explain the formation of a black hole in the mass gap caused by (pulsational) pair-instability, $M = 65-…
The Final Fate of Supermassive Pop III Stars: Explosion or Collapse?
Chris Nagele, Hideyuki Umeda, Koh Takahashi +2
We investigate the possibility of a supernova in supermassive () population III stars induced by a general relativistic instability occurring in the helium…
First Detection of X-Ray Line Emission from Type IIn Supernova 1978K with XMM-Newton's RGS
Y. Chiba, S. Katsuda, T. Yoshida +2
We report on robust measurements of elemental abundances of the Type IIn supernova SN 1978K, based on the high-resolution X-ray spectrum obtained with the Reflection Grating Spectr…
Matter Mixing in Aspherical Core-collapse Supernovae: Three-dimensional Simulations with Single Star and Binary Merger Progenitor Models for SN 1987A
Masaomi Ono, Shigehiro Nagataki, Gilles Ferrand +5
We perform three-dimensional hydrodynamic simulations of aspherical core-collapse supernovae focusing on the matter mixing in SN 1987A. The impacts of four progenitor (pre-supernov…
The possible role of stellar mergers for the formation of multiple stellar populations in globular clusters
Long Wang, Pavel Kroupa, Koh Takahashi +1
Many possible scenarios for the formation of multiple stellar populations (MSP) in globular clusters (GCs) have been discussed so far, including the involvement of asymptotic giant…
Fitting formulae for evolution tracks of massive stars under extreme metal poor environments for population synthesis calculations and star cluster simulations
Ataru Tanikawa, Takashi Yoshida, Tomoya Kinugawa +2
We have devised fitting formulae for evolution tracks of massive stars with under extreme metal poor (EMP) environments for $\log (Z/Z_\odot) =…
One-, Two-, and Three-dimensional Simulations of Oxygen Shell Burning Just Before the Core-Collapse of Massive Stars
Takashi Yoshida, Tomoya Takiwaki, Kei Kotake +3
We perform two- (2D) and three-dimensional (3D) hydrodynamics simulations of convective oxygen shell-burning that takes place deep inside a massive progenitor star of a core-collap…
Gravitational waves from very massive stars collapsing to a black hole
Haruki Uchida, Masaru Shibata, Koh Takahashi +1
We compute gravitational waves emitted by the collapse of a rotating very massive star (VMS) core leading directly to a black hole in axisymmetric numerical-relativity simulations.…
The Evolution towards Electron-capture Supernovae: the Flame Propagation and the Pre-bounce Electron-neutrino Radiation
K. Takahashi, K. Sumiyoshi, S. Yamada +2
A critical mass ONe core with a high ignition density is considered to end in gravitational collapse leading to neutron star formation. Being distinct from a Fe core collapse, the…
Black Hole Formation and Explosion from Rapidly Rotating Very Massive Stars
Haruki Uchida, Masaru Shibata, Koh Takahashi +1
We explore the formation process of a black hole (BH) through the pair-instability collapse of a rotating Population III very massive star in axisymmetric numerical relativity. As…
On the minimum mass of neutron stars
Yudai Suwa, Takashi Yoshida, Masaru Shibata +2
We investigate remnant neutron star masses (in particular, the minimum allowed mass) by performing advanced stellar evolution calculations and neutrino-radiation hydrodynamics simu…
The Low Detection Rate of Pair Instability Supernovae and the Effect of the Core Carbon Fraction
Koh Takahashi
The pair instability supernova (PISN) is a common fate of very massive stars (VMSs). Current theory predicts the initial and the CO core mass ranges for PISNe of 140-260 $M_\…