Gamma-ray bursts from evolved galactic nuclei

A new cosmological scenario for the origin of gamma-ray bursts (GRBs) is pr oposed. In our scenario, a highly evolved central core in the dense galacti c nucleus is formed, containing a subsystem of compact stellar remnants (CS Rs), such as neutron stars and black holes. Those subsystems result from th e dynamical evolution of dense central stellar clusters in the galactic nuc lei through merging of stars, thereby forming (as has been realized by many authors) the short-lived massive stars and then CSRs. We estimate the rate of random CSR collisions in the evolved galactic nuclei by taking into acc ount, in a procedure similar to that of Quinlan & Shapiro, the dissipative encounters of CSRs, mainly due to radiative losses of gravitational waves, which result in the formation of intermediate short-lived binaries, with fu rther coalescence of the companions to produce GRBs. We also consider how t he possible presence of a central supermassive black hole, formed in a high ly evolved galactic nucleus, influences the CSR binary formation. This scen ario does not postulate ad hoc a required number of tight binary neutron st ars in the galaxies. Instead, it gives, for the most realistic parameters o f the evolved nuclei, the expected rate of GRBs consistent with the observe d one, thereby explaining the GRB appearance as a natural part of the dynam ical evolution of galactic nuclei. In addition, this scenario provides an o pportunity for a cosmological GRB recurrence, previously considered to be a distinctive feature of GRBs of a local origin only. We also discuss some o ther observational tests of the proposed scenario.