J-GLOBAL         Last updated: Feb 23, 2017 at 16:49
The University of Tokyo
Graduate School of Science Research Center for The Early Universe
Job title
Associate Professor
Doctor of Science

Research Areas


Academic & Professional Experience

: JSPS Fellow Ship
: Max-Planck Institute for Astrophysik, Guest Researcher
: Research Associate, Faculty of Science, Univ. of Tokyo
: Associate Prof., Graduate School of Science, Univ. of Tokyo


University of Tokyo, Graduate School of Science, Department of Astronomy
Department of Astronomy, Faculty of Science, University of Tokyo

Published Papers

Akihiro Suzuki, Keiichi Maeda, Toshikazu Shigeyama
   Oct 2016
Hydrodynamical interaction of spherical ejecta freely expanding at mildly
relativistic speeds into an ambient cold medium is studied in semi-analytical
and numerical ways to investigate how ejecta produced in energetic stellar
explosions dissipate...
Yutaka Komiya, Toshikazu Shigeyama
   Aug 2016
The main astronomical source of r-process elements has not yet been
identified. One plausible site is neutron star mergers (NSMs), but from
perspective of the Galactic chemical evolution, it has been pointed out that
NSMs cannot reproduce the obse...
Akihiro Suzuki, Keiichi Maeda, Toshikazu Shigeyama
   May 2016
A two-dimensional special relativistic radiation-hydrodynamics code is
developed and applied to numerical simulations of supernova shock breakout in
bipolar explosions of a blue supergiant. Our calculations successfully simulate
the dynamical evol...
Miyu Masuyama, Toshikazu Shigeyama, Yoichiro Tsuboki
   Dec 2015
We present a novel semi-analytic solution describing the propagation of a
spherical blast wave driven by a central energy source. The initial density
profile has a power-law function of the distance from the center and the energy
is injected only ...
Kazuhiro Noda, Takuma Suda, Toshikazu Shigeyama
   Nov 2015
The progenitor systems for type Ia supernovae are still controversial. One of
the methods to test the proposed scenario for the progenitor systems is to
identify companions that are supposed to survive according to the so-called
single degenerate ...
Takuji Tsujimoto, Miho N. Ishigaki, Toshikazu Shigeyama, Wako Aoki
   Apr 2015
Chemical abundance of r-process elements in nearby dwarf spheroidal (dSph)
galaxies is a powerful tool to probe the site of r-process since their
small-mass scale can sort out individual events producing r-process elements. A
merger of binary neut...
Masamichi Kutsuna, Toshikazu Shigeyama
   Apr 2015
In the single degenerate (SD) scenario of type Ia supernovae (SNe Ia), the
collision of the ejecta with its companion results in stripping hydrogen rich
matter from the companion star. This hydrogen rich matter might leave its trace
in the light c...
Takuji Tsujimoto, Toshikazu Shigeyama
   Oct 2014
Growing interests in neutron star (NS) mergers as the origin of r-process
elements have sprouted since the discovery of evidence for the ejection of
these elements from a short-duration gamma-ray burst. The hypothesis of a NS
merger origin is rein...
Akihiro Suzuki, Toshikazu Shigeyama
   Sep 2014
We investigate the hydrodynamical evolution of an ultra-relativistic fireball
colliding with a freely expanding gas. The hydrodynamical interaction of the
fireball and the gas results in the formation of a geometrically thin shell. We
study the dy...
Keiichi Maeda, Masamichi Kutsuna, Toshikazu Shigeyama
   Aug 2014
While type Ia Supernovae (SNe Ia) have been used as precise cosmological
distance indicators, their progenitor systems remain unresolved. One of the key
questions is if there is a non-degenerate companion star at the time of a
thermonuclear explos...
Takuji Tsujimoto, Toshikazu Shigeyama
   May 2014
The origin of r-process elements remains unidentified and still puzzles us.
The recent discovery of evidence for the ejection of r-process elements from a
short-duration gamma-ray burst singled out neutron star mergers (NSMs) as their
origin. In c...
Yukari Ohtani, Mikio Morii, Toshikazu Shigeyama
   Apr 2014
We investigate the mechanism to reproduce notable spectral features at the
ignition phase of nova explosion observed for a super-Eddington X-ray transient
source MAXI J0158Tex744 in the Small Magellanic Cloud. These are a strong Ne IX
emission lin...
Nobutoshi Yasutake, Kei Kotake, Masamichi Kutsuna, Toshikazu Shigeyama
   Jan 2014
Bearing in mind the application to high-magnetic-field (high-B) radio
pulsars, we investigate two-dimensional (2D) thermal evolutions of neutron
stars (NSs). We pay particular attention to the influence of different
equilibrium configurations on t...
Ryo Tsutsui, Toshikazu Shigeyama
   Nov 2013
Analyzing light curves of a complete sample of bright Swift long gamma-ray
bursts (LGRBs) of which the peak photon fluxes constructed with the bin width
of 1 second in the Swift 15-350 keV energy band exceed 2.6 photons
cmTexsTex, we confi...
Yukari Ohtani, Akihiro Suzuki, Toshikazu Shigeyama
   Sep 2013
We present theoretical expectations for non-thermal emission due to the bulk
Comptonization at the ultra-relativistic shock breakout. We calculate the
transfer of photons emitted from the shocked matter with a Monte Carlo code
fully taking into ac...
Ryo Tsutsui, Toshikazu Shigeyama
   Apr 2013
Overwhelming diversity of long gamma-ray bursts (LGRBs), discovered after the
launch of {\it Swift} satellite, is a major obstacle to LGRB studies. Recently,
it is shown that the prompt emission of LGRBs is classified into three
subclasses: Type I...
Akihiro Suzuki, Toshikazu Shigeyama
   Jan 2013
We performed a series of hydrodynamical calculations of an ultra-relativistic
jet propagating through a massive star and the circumstellar matter to
investigate the interaction between the ejecta and the circumstellar matter. We
succeed in disting...
Takuji Tsujimoto, Toshikazu Shigeyama
   Oct 2012
A time delay of Type Ia supernova (SN Ia) explosions hinders the imprint of
their nucleosynthesis on stellar abundances. However, some occasional cases
give birth to stars that avoid enrichment of their chemical compositions by
massive stars and t...
Toshikazu Shigeyama, Akihiro Suzuki, Ko Nakamura
Publicaton of Astronomical Society of Japan   65(5)    Oct 2012   [Refereed]
We present a new self-similar solution describing early evolution of an
ultra-relativistic flow resulting from a collision of homologously expanding
spherical ejecta with the circumstellar matter, in which a shock wave
propagates in the circumstel...
Masamichi Kutsuna, Toshikazu Shigeyama
The Astrophysical Journal   749 51   Apr 2012   [Refereed]
We investigate effects of the magnetic field on the propagation of laminar
flames of nuclear reactions taking place in white dwarfs (WDs) with the mass
close to the Chandrasekhar limit. We calculate the velocities of laminar flames
parallel and pe...
Akihiro Suzuki, Toshikazu Shigeyama
The Astrophysical Journal Letters   723(1,Pt.2) L84-L88   Nov 2010   [Refereed]
To account for the non-thermal emission from the classical nova V2491 Cygni,
we perform a series of numerical calculations of radiative transfer of
\gamma-ray photons from the radioactive isotope TexNa in the matter ejected
from a white dwarf....
Ko Nakamura, Takashi Yoshida, Toshikazu Shigeyama, Toshitaka Kajino
The Astrophysical Journal Letters   718(2) L137-L140   Aug 2010   [Refereed]
We investigate the neutrino-process in an energetic Type Ic supernova (SN Ic)
and resultant productions of the light elements including boron and its stable
isotopes. SN Ic is a very unique boron source because it can produce boron
through not onl...
Akihiro Suzuki, Toshikazu Shigeyama
The Astrophysical Journal   719(1,Pt.1) 881-889   Aug 2010   [Refereed]
We investigate roles of the bulk comptonization process in the propagation of
thermal photons emitted at the shock breakout of a supernova explosion. We use
a hydrodynamical model based on a self-similar solution for the shock breakout.
The propag...
Akihiro Suzuki, Toshikazu Shigeyama
The Astrophysical Journal Letters   717(2,Pt.2) L154-L158   Jul 2010   [Refereed]
We investigate effects of aspherical energy deposition in core-collapse
supernovae on the light curve of the supernova shock breakout. We performed
two-dimensional hydrodynamical calculations of an aspherical supernova
explosion to obtain the time...
Takashi Moriya, Toshikazu Shigeyama
Physical Review D   81(4) 043004   Feb 2010   [Refereed]
A new mechanism for enhancing the helium abundance in the blue main sequence
stars of omega Centauri and NGC 2808 is investigated. We suggest that helium
enhancement was caused by the inhomogeneous big bang nucleosynthesis. Regions
with extremely ...
Akihiro Suzuki, Toshikazu Shigeyama
J.Comput.Phys.   229(5) 1643-1660   Mar 2010   [Refereed]
A new scheme for numerical integration of the 1D2V relativistic
Vlasov-Maxwell system is proposed. Assuming that all particles in a cell of the
phase space move with the same velocity as that of the particle located at the
center of the cell at th...
Akihiro Suzuki, Toshikazu Shigeyama
The Astrophysical Journal   695(2) 1550-1558   Apr 2009   [Refereed]
We present results of a 2D3V kinetic Vlasov simulation of the Weibel
instability. The kinetic Vlasov simulation allows us to investigate the
velocity distribution of dilute plasmas, in which the effect of collisions
between particles is negligible...
Akihiro Suzuki, Toshikazu Shigeyama
Physics of Plasmas   15(4) 042107   Apr 2008   [Refereed]
A novel method to derive stationary solutions of the Vlasov-Maxwell system is
established. This method is based on the assumption that the deviation of the
velocity distribution from the Maxwell-Boltzmann distribution can be expanded
by the Hermit...
Takuma Suda, Takuji Tsujimoto, Toshikazu Shigeyama, Masayuki Y. Fujimoto
The Astrophysical Journal   671(2) L129-L132   Dec 2007   [Refereed]
The unveiled main-sequence splitting in omega Centauri as well as NGC 2808
suggests that matter highly-enriched in He (in terms of its mass fraction
Y~0.4) was produced and made the color of some main-sequence stars bluer in
these globular cluster...
Yutaka Ihara, Jin Ozaki, Mamoru Doi, Toshikazu Shigeyama, Nobunari Kashikawa, Yutaka Komiyama, Takashi Hattori
PASJ   59(4) 811-826   Aug 2007   [Refereed]
We report our first results of photometric and spectroscopic observations for
Tycho's supernova remnant (SNR Tycho) to search for the companion star of a
type Ia supernova (SN Ia). From photometric observations using Suprime-Cam on
the Subaru Tele...
Akihiro Suzuki, Toshikazu Shigeyama
The Astrophysical Journal   661(1) 385-393   May 2007   [Refereed]
We present a self-similar solution to describe the propagation of a shock
wave whose energy is deposited or lost at the front. Both of the propagation of
the shock wave in a medium having a power-law density profile and the expansion
of the medium...
Reina Kikuchi, Toshikazu Shigeyama
Astrophys.J.   657(2) 860-869   Mar 2007   [Refereed]
We investigate relativistic flows after a shock wave generated in a star
arrives at the surface. First, the sphericity effect is involved through a
successive approximation procedure by adding correction terms to an already
known self-similar solu...
Takuji Tsujimoto, Toshikazu Shigeyama, Takuma Suda
The Astrophysical Journal   654(2) L139-L142   Jan 2007   [Refereed]
The origin of a double main-sequence (MS) in omega Centauri is explored. We
have shown from theoretical calculations on the stellar evolution that the
colors of MS stars are shifted to those of the observed blue MS if the surface
layers are pollut...
Yutaka Komiya, Takuma Suda, Hiroki Minaguchi, Toshikazu Shigeyama, Wako Aoki, Masayuki Y. Fujimoto
Astrophys.J.   658(1) 367-390   Mar 2007   [Refereed]
It is known that the carbon-enhanced, extremely metal-poor (CEMP) stars
constitute a substantial proportion in the extremely metal-poor (EMP) stars of
the Galactic Halo, by far larger than CH stars in Population II stars. We
investigate their orig...
Ko Nakamura, Toshikazu Shigeyama
Astrophys.J.   645(1) 431-435   Jul 2006   [Refereed]
We find self-similar solutions to describe the interaction of spherically
symmetric ejecta expanding at relativistic speeds with an ambient medium having
a power law density distribution. Using this solution, the time evolution of
the Lorentz fact...
Jin Ozaki, Toshikazu Shigeyama
Astrophys.J.   644(2) 954-958   Jun 2006   [Refereed]
We propose a method to identify the companion stars of type Ia supernovae
(SNe Ia) in young supernova remnants (SNRs) by recognizing distinct features of
absorption lines due to Fe I appearing in the spectrum. If a sufficient amount
of Fe I remain...
Ko Nakamura, Susumu Inoue, Shinya Wanajo, Toshikazu Shigeyama
Astrophys.J.   643(2) L115-L118   Jun 2006   [Refereed]
We investigate energetic type Ic supernovae as production sites for Li6 and
Be in the early stages of the Milky Way. Recent observations have revealed that
some very metal-poor stars with [Fe/H]<-2.5 possess unexpectedly high
abundances of Li6. So...
Takuji Tsujimoto, Toshikazu Shigeyama
Astrophys.J.   638(2) L109-L112   Feb 2006   [Refereed]
Renewed interest in the first stars that were formed in the universe has led
to the discovery of extremely iron-poor stars. Since several competing
scenarios exist, our understanding of the mass range that determines the
observed elemental abundan...
Kazunori Nakayama, Toshikazu Shigeyama
Astrophys.J. 627 (2005) 310-318   627(1) 310-318   Jul 2005   [Refereed]
We study the evolution of the ultra-relativistic shock wave in a
plane-parallel atmosphere adjacent to a vacuum and the subsequent breakout
phenomenon. When the density distribution has a power law with the distance
from the surface, there is a se...
Ko Nakamura, Toshikazu Shigeyama
Astrophys.J.   610(2) 888-896   Aug 2004   [Refereed]
Explosions of type Ic supernovae (SNe Ic) are investigated using a
relativistic hydrodynamic code to study roles of their outermost layers of the
ejecta in light element nucleosynthesis through spallation reactions as a
possible mechanism of the "...
Toshikazu Shigeyama, Takuji Tsujimoto
Astrophys.J.   598(1) L47-L50   Nov 2003   [Refereed]
The origin of low alpha/Fe ratios in some metal-poor stars, so called
low-alpha stars, is discussed. It is found that most of low-alpha stars in the
Galaxy are on the main-sequence. This strongly suggests that these stars
suffered from external po...
Toshikazu Shigeyama, Takuji Tsujimoto, Yuzuru Yoshii
Astrophys.J.   586(1) L57-L60   Mar 2003   [Refereed]
The external pollution of the first stars in the Galaxy is investigated. The
first stars were born in clouds composed of the pristine gas without heavy
elements. These stars accreted gas polluted with heavy elements while they
still remained in th...
Takuji Tsujimoto, Toshikazu Shigeyama
Astrophys.J.   590(2) 803-808   Jun 2003   [Refereed]
The star formation history of the globular cluster Omega Centauri is
investigated in the context of an inhomogeneous chemical evolution model in
which supernovae induce star formation. The proposed model explains recent
observations for Omega Cen ...
Takuji Tsujimoto, Toshikazu Shigeyama
Astrophys.J.   584(2) L87-L90   Feb 2003   [Refereed]
The unique elemental abundance pattern of the carbon-rich stars CS29498-043
and CS22949-037 is characterized by a large excess of magnesium and silicon in
comparison with iron. This excess is investigated in the context of a
supernova-induced star...
Takuji Tsujimoto, Toshikazu Shigeyama
The Astrophysical Journal   571(2) L93-L97   Jun 2002   [Refereed]
Stellar abundance pattern of neutron-capture elements such as barium is used
as a powerful tool to infer how star formation proceeded in dwarf spheroidal
(dSph) galaxies. It is found that the abundance correlation of barium with iron
in stars belo...
Takuji Tsujimoto, Toshikazu Shigeyama
The Astrophysical Journal   561(1) L97-L100   Nov 2001   [Refereed]
The origin of nucleosynthesis products of rapid neutron capture reactions
(the r-process) is a longstanding astrophysical problem. Recent analyses of
elemental abundances for extremely metal-poor stars shed light on the elemental
abundances of ind...
Takuji Tsujimoto, Toshikazu Shigeyama, Yuzuru Yoshii
The Astrophysical Journal   565(2) 1011-1016   Feb 2002   [Refereed]
We investigate the chemical evolution of odd-numbered elements such as sodium
(Na) and aluminum (Al) during the early epochs of the Galactic halo with the
use of a model that reproduces the observed box-shaped distribution of
extremely metal-poor ...
Naohito Nakasato, Toshikazu Shigeyama
The Astrophysical Journal   541(2) L59-L62   Oct 2000   [Refereed]
The long-term evolution of supernova remnants (SNRs) in the primordial
interstellar medium (ISM) with an inhomogeneous structure is calculated to
investigate metal enrichment of the primordial gas. For this purpose, we have
constructed a parallel ...
Takuji Tsujimoto, Toshikazu Shigeyama, Yuzuru Yoshii
The Astrophysical Journal   531(1) L33-L36   Mar 2000   [Refereed]
We suggest that if the astrophysical site for r-process nucleosynthesis in
the early Galaxy is confined to a narrow mass range of Type II supernova (SN
II) progenitors, with a lower mass limit of Mms = 20 Msun, a unique feature in
the observed dis...
Takuji Tsujimoto, Toshikazu Shigeyama, Yuzuru Yoshii
The Astrophysical Journal   519(1) L63-L67   Jul 1999   [Refereed]
A model for Galactic chemical evolution, driven by supernova-induced star
formation, is formulated and used to examine the nature of the Galactic halo at
early epochs. In this model, new stars are formed following each supernova
event, thus their ...
Takuji Tsujimoto, Toshikazu Shigeyama
The Astrophysical Journal   508(2) L151-L154   Dec 1998   [Refereed]
The supernova yields of several heavy elements including alpha-, iron-group,
and r-process elements are obtained as a function of the mass of their
progenitor main-sequence stars M_ms from the abundance patterns of extremely
metal-poor stars with ...
Toshikazu Shigeyama, Takuji Tsujimoto
The Astrophysical Journal   507(2) L135-L139   Nov 1998   [Refereed]
Using results of nucleosynthesis calculations for theoretical core-collapse
supernova models with various progenitor's masses, it is shown that abundance
patterns of C, Mg, Si, Ca, and H seen in extremely metal-deficient stars with
[Fe/H] < -2.5 f...
Implications of the Recent Light Curve of SN 1987A
Shiomi Kumagai, Toshikazu Shigeyama, Ken'ichi Nomoto, Masa-aki Hashimoto
Astronomy and Astrophysics   243(2) L13-L16   Mar 1991   [Refereed]
Rayleigh-Taylor Instabilities and Mixing in the Helium Star Models for Type Ib/Ic Supernovae
Hachisu, Izumi; Matsuda, Takuya; Nomoto, Ken'ichi; Shigeyama, Toshikazu
Astrophysical Journal(Letters)   368 L27-L30   Feb 1991   [Refereed]
The Type Ic Supernava 1987M: Core Collapse of a Low-Mass Helium Star in a Binary System
Ken'ichi Nomoto, Alexei V. Filippenko, Toshikazu Shigeyama
Astronomy and Astrophysics   240(1) L1-L4   Dec 1990   [Refereed]
Low Mass Helium Star Models for Type Ib Supernovae: Light Curves, Mixing, and Nucleosynthesis
Shigeyama, Toshikazu; Nomoto, Ken'ichi; Tsujimoto, Takuji; Hashimoto, Masa-Aki
Astrophysical Journal(Letters)   361 L23-L27   Sep 1990   [Refereed]
Theoretical Light Curve of Supernova 1987A and Mixing of Hydrogen and Nickel in the Ejecta
Toshikazu Shigeyama, Ken'ichi Nomoto
Astrophysical Journal   360 242-256   Sep 1990   [Refereed]
Nonlinear Growth of Rayleigh-Taylor Instabilities and Mixing in SN 1987A
Hachisu, Izumi; Matsuda, Takuya; Nomoto, Ken'ichi; Shigeyama, Toshikazu
Astrophysical Journal(Letters)   358 L57-L61   Aug 1990   [Refereed]
Gamma-Rays, X-Rays and Optical Light from the Cobalt and the Neutron Star in SN 1987A
Kumagai, Shiomi; Shigeyama, Toshikazu; Nomoto, Ken'ichi; Itoh, Masayuki; Nishimura, Jun; Tsuruta, Sachiko
Astrophysical Journal   345 412-422   Oct 1989   [Refereed]
Rayleigh-Taylor Instability and Mixing in SN 1987A
Toshikazu Ebisuzaki, Toshikazu Shigeyama, Ken'ichi Nomoto
Astrophysical Journal(Letters)   344 L65-L68   Sep 1989   [Refereed]
Explosive Nucleosynthesis in Supernova 1987A
Masaaki Hashimoto, Ken'ichi Nomoto, Toshikazu Shigeyama
Astronomy and Astrophysics   210(1-2) L5-L8   Feb 1989   [Refereed]
Hard X-Rays and Gamma-Rays from SN 1987A and Mixing of the Supernova Ejecta,
Shiomi Kumagai, Toshikazu Shigeyama, Ken'ichi Nomoto, Masayuki Itoh, Jun Nishimura
Astronomy and Astrophysics   197(1-2) L7-L10   May 1988   [Refereed]
Hydrodynamical Models and the Light Curve of Supernova 1987A in the LMC
Toshikazu Shigeyama, Ken'ichi Nomoto, Masaaki Hashimoto
Astronomy and Astrophysics   196(1-2) 141-151   May 1988   [Refereed]
Masayuki Itoh, Shiomi Kumagai, Toshikazu Shigeyama, Ken'ichi Nomoto, Jun Nishimura
Nature   330(6145) 233-235   Nov 1987   [Refereed]
Toshikazu Shigeyama, Ken'ichi Nomoto, M. Hashimoto, Daiichiro Sugimoto
Nature   328(6128) 320-323   Jul 1987   [Refereed]


Numerical Solution of the Equation of Radiative Equilibrium
Publication of Astronomical Society of Japan (1984), 36, 593-601   
Light-Curve Models for Supenova 1987A in the Large Magellanic Cloud
Nature (1987), 328, 320-323   
X-Rays Expected from SN 1987A Compared with the Source Discovered by the Ginga Satellite
Nature (1987), 330, 233-235   
Hydrodynamical Models and the Light Curve of Supernova 1987A in the LMC
Astronomy and Astrophysics (1988), 196, 141-151   
Hard X-Rays and Gamma-Rays from SN 1987A and Mixing of the Supernova Ejecta,
Astronomy and Astrophysics (1988), 197, L7-L10   

Research Grants & Projects

Explosion mechanism of supernovae
Ordinary Research
Project Year: 1987   
Chemical Evolution of Galaxies
Ordinary Research
Project Year: 1998