Bibcode
Bethe, H. A.; Israelian, G.; Lee, H. K.; Wijers, R. A. M. J.; Lee, C.-H.; Brown, G. E.
Referencia bibliográfica
New Astronomy, Volume 5, Issue 4, p. 191-210.
Fecha de publicación:
7
2000
Revista
Número de citas
113
Número de citas referidas
86
Descripción
Recent observations and theoretical considerations have linked gamma-ray
bursts with ultra-bright type Ibc supernovae (`hypernovae'). We here
work out a specific scenario for this connection. Based on earlier work,
we argue that especially the longest bursts must be powered by the
Blandford-Znajek mechanism of electromagnetic extraction of spin energy
from a black hole. Such a mechanism requires a high angular momentum in
the progenitor object. The observed association of gamma-ray bursts with
type Ibc supernovae leads us to consider massive helium stars that form
black holes at the end of their lives as progenitors. In our analysis we
combine the numerical work of MacFadyen & Woosley with analytic
calculations in Kerr geometry, to show that about 10 53 erg
each are available to drive the fast GRB ejecta and the supernova. The
GRB ejecta are driven by the power output through the open field lines
threading the black hole, whereas the supernova can be powered both by
the shocks driven into the envelope by the jet, and by the power
delivered into the disk via field lines connecting the disk with the
black hole. We also present a much simplified approximate derivation of
these energetics. Helium stars that leave massive black-hole remnants
can only be made in fairly specific binary evolution scenarios, namely
the kind that also leads to the formation of soft X-ray transients with
black-hole primaries, or in very massive WNL stars. Since the binary
progenitors will inevitably possess the high angular momentum we need,
we propose a natural link between black-hole transients and gamma-ray
bursts. Recent observations of one such transient, GRO J1655-40/Nova
Scorpii 1994, explicitly support this connection: its high space
velocity indicates that substantial mass was ejected in the formation of
the black hole, and the overabundance of α-nuclei, especially
sulphur, indicates that the explosion energy was extreme, as in SN
1998bw/GRB 980425. Furthermore, X-ray studies of this object indicate
that the black hole may still be spinning quite rapidly, as expected in
our model. We also show that the presence of a disk during the powering
of the GRB and the explosion is required to deposit enough of the
α nuclei on the companion.