Effect of kick velocity on the gamma-ray burster distribution
May, 199515 pages
Published in:
- Astron.Astrophys. 313 (1996) 197-203
e-Print:
- astro-ph/9505119 [astro-ph]
Report number:
- FERMILAB-PUB-95-134-A
View in:
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Abstract: (arXiv)
The effect of kick velocity to newly born pulsars on the distribution of -ray bursters is examined in the context of the disk origin model and the halo model of the -ray bursters. The conversion formula from a two-dimensional velocity distribution function to a three-dimensional distribution function is derived and it is applied to reproduce the distributionfunction of the kick velocity of radio pulsars. Monte Carlo simulations of the kicked neutron stars show that the disk neutron star model of the -ray bursters still needs unnatural assumptions if the velocity distribution of the -ray bursters is same with that of neutron stars; only the neutron stars with very high kick velocity could become the -ray bursters and there are silent majorities. On the other hand, the core radius of -ray bursters is found not to be extended by the kick velocity if the core-halo structure similar to the Galactic dark matter distribution is assumed on the initial distribution of the halo neutron stars. Thus the kick velocity to the neutron stars do not improve the statistics both of the disk model and the halo model. Two possibilities to save the Galactic models are suggested: (1) The ray bursters are old neutron stars which were accelerated to be faster than by jet propulsion and passed the death line for pulsars due to the spin down caused by the rotational energy loss by the jet ejection. (2) The initial distribution of the neutron stars is fairly uniform and the extent of the halo is large enough for the halo model to be consistent with the observations. It implies that the initial star formation burst of the Galaxy occurred fairly uniformly in the extended halo region.References(15)
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