Origin of GRB Afterglows in the Model of Galactic Neutron Stars

The launch of the Beppo-Sax satellite gave a unique opportunity to investigate gamma ray bursts (GRB) in different spectral regions. The large diversity of the afterglow behavior creates additional problems for the cosmological model with a fireball. Formation of the afterglow giving the observed diversity of properties is suggested in the Galactic neutron star model of GRBs. It is based on the transient accretion disc formation around the neutron star with a low-mass brown companion irradiated by the neutron star.Comment: Talk at the Workshop "Gamma-Ray Bursts in the Afterglow Era", Rome, November 3-6. To appear in A&A Supp

High Velocity Neutron Stars as a Result of Asymmetric Neutrino Emission

Formation of a neutron star is accompanied by neutrino emission carring about 10% of the rest energy of the star. Toroidal field produced by twisting of a dipole field in differentially rotating star is antisymmetric. Its summation with antisymmetric toroidal field results in braking of mirror symmetry of the magnetic field . For large magnetic field the neutron decay rate depends on its strength. Neutrino is emitted more in one direction leading to flux asymmetry and recoil of the neutron star. Estimations show that the neutron star can reach velocities $\sim 1000$ km/s for 3% asymmetry of the neutrino flux.Comment: Latex, no figures, 5 page

Gamma Ray Bursts statistical properties and limitations on the physical model

The present common view about GRB origin is related to cosmology. There are two evidences in favour of this interpretation. The first is connected with statistics, the second is based on measurements of the redshifts in the GRB optical afterglows. Red shifts in optical afterglows had been observed only in long GRB. Statistical errors, and possibility of galactic origin of short GRB is discussed; their connection with Soft Gamma Repeaters (SGR) is analyzed.Comment: 4 pages, submitted to the Proc. of the XX Texas Symposiu