Issue |
A&A
Volume 376, Number 2, September II 2001
|
|
---|---|---|
Page(s) | 568 - 579 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20010993 | |
Published online | 15 September 2001 |
Spherical collapse of supermassive stars: Neutrino emission and gamma-ray bursts
1
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
2
School of Computer Science and Mathematics, University of Portsmouth, P01 2EG, Portsmouth, UK
Corresponding author: J. A. Font, font@mpa-garching.mpg.de
Received:
9
March
2001
Accepted:
6
July
2001
We present the results of numerical simulations of the
spherically symmetric gravitational collapse of supermassive stars
(SMS). The collapse is studied using a general relativistic
hydrodynamics code. The coupled system of Einstein and fluid
equations is solved employing coordinates adapted to a foliation of
the spacetime by means of outgoing null hypersurfaces. The
code contains an equation of state which includes effects due to
radiation, electrons and baryons, and detailed microphysics to
account for electron-positron pairs. In addition energy losses by
thermal neutrino emission are included. We are able to follow the
collapse of SMS from the onset of instability up to the point of
black hole formation. Several SMS with masses in the range
are simulated. In all models an
apparent horizon forms initially, enclosing the innermost 25% of
the stellar mass. From the computed neutrino luminosities, estimates
of the energy deposition by
-annihilation are
obtained. Only a small fraction of this energy is deposited near the
surface of the star, where, as proposed recently by Fuller & Shi
([CITE]), it could cause the ultrarelativistic flow believed to be
responsible for γ-ray bursts. Our simulations show that for
collapsing SMS with masses larger than
the
energy deposition is at least two orders of magnitude too small to
explain the energetics of observed long-duration bursts at
cosmological redshifts. In addition, in the absence of rotational
effects the energy is deposited in a region containing most of the
stellar mass. Therefore relativistic ejection of matter is
impossible.
Key words: hydrodynamics / methods: numerical / relativity / gamma rays: bursts / elementary particles / neutrinos
© ESO, 2001
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