Gamma‐Ray Bursts from Evolved Galactic Nuclei

A new cosmological scenario for the origin of gamma ray bursts (GRBs) isproposed. In our scenario, a highly evolved central core in the dense galacticnucleus is formed containing a subsystem of compact stellar remnants (CSRs),such as neutron stars and black holes. Those subsystems result from thedynamical evolution of dense central stellar clusters in the galactic nucleithrough merging of stars, thereby forming (as has been realized by manyauthors) the short-living massive stars and then CSRs. We estimate the rate ofrandom CSR collisions in the evolved galactic nuclei by taking into account,similar to Quinlan & Shapiro (1987), the dissipative encounters of CSRs, mainlydue to radiative losses of gravitational waves, which results in the formationof intermediate short-living binaries, with further coalescence of thecompanions to produce GRBs. We also consider how the possible presence of acentral supermassive black hole, formed in a highly evolved galactic nucleus,influences the CSR binary formation. This scenario does not postulate ad hoc arequired number of tight binary neutron stars in the galaxies. Instead, itgives, for the most realistic parameters of the evolved nuclei, the expectedrate of GRBs consistent with the observed one, thereby explaining the GRBappearance in a natural way of the dynamical evolution of galactic nuclei. Inaddition, this scenario provides an opportunity for a cosmological GRBrecurrence, previously considered to be a distinctive feature of GRBs of alocal origin only. We also discuss some other observational tests of theproposed scenario.Comment: 25 pages, LATEX, uses aasms4.sty, accepted by Ap