It has been suggested by Usov (1992) that accreting white dwarfs, collapsing to neutron stars may be the sources of the gamma-ray bursts observed at cosmological distances, provided they rotate very fast and have enormously high magnetic fields. In this model the burst's duration r is given by the ratio of pulsar kinetic energy and magneticdipole luminosity, so that in order to account for the shortest (r ,,~ 0.1 s) bursts, the pulsars must rotate very fast (with period P ,-~ 0.5 ms) and have magnetic fields of 1016 - 101T G. Though the high pulsar frequency was anticipated (Qadir and Rafique, 1986) and has been shown to be plausible (Abramowicz, 1990), the extremely high magnetic fields seem anomalous as observed neutron stars have fields below ~ 1013 G. The problem with Usov's proposal is reduced by incorporating the relativistic corrections for fast rotating magnetic dipoles (Belinsky et al., 1994) or magnetic stars (De Paolis and Qadir, 1994). These corrections substantially enhance the radiation efficiency due to the existence of a magnetic synchrotron effect so that the magnetic field required for the explanation of the shortest gamma-ray bursts is strongly reduced. As such the model becomes much more plausible.
Collapsed white dwarfs as gamma-ray bursts sources
DE PAOLIS, Francesco;INGROSSO, Gabriele;
1995-01-01
Abstract
It has been suggested by Usov (1992) that accreting white dwarfs, collapsing to neutron stars may be the sources of the gamma-ray bursts observed at cosmological distances, provided they rotate very fast and have enormously high magnetic fields. In this model the burst's duration r is given by the ratio of pulsar kinetic energy and magneticdipole luminosity, so that in order to account for the shortest (r ,,~ 0.1 s) bursts, the pulsars must rotate very fast (with period P ,-~ 0.5 ms) and have magnetic fields of 1016 - 101T G. Though the high pulsar frequency was anticipated (Qadir and Rafique, 1986) and has been shown to be plausible (Abramowicz, 1990), the extremely high magnetic fields seem anomalous as observed neutron stars have fields below ~ 1013 G. The problem with Usov's proposal is reduced by incorporating the relativistic corrections for fast rotating magnetic dipoles (Belinsky et al., 1994) or magnetic stars (De Paolis and Qadir, 1994). These corrections substantially enhance the radiation efficiency due to the existence of a magnetic synchrotron effect so that the magnetic field required for the explanation of the shortest gamma-ray bursts is strongly reduced. As such the model becomes much more plausible.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
