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Evolution of the double neutron star merging rate and the cosmological origin of gamma-ray burst sources

V.M.Lipunov tex2html_wrap_inline158 , K.A.Postnov tex2html_wrap_inline158 , M.E.Prokhorov tex2html_wrap_inline170 ,
I.E.Panchenko tex2html_wrap_inline168 , and H.E. Jorgensen tex2html_wrap_inline172

tex2html_wrap_inline168 Faculty of Physics, Moscow University, 117234 Moscow, Russia
tex2html_wrap_inline170 Sternberg Astronomical Institute, Moscow University, 119899 Moscow, Russia
tex2html_wrap_inline172 Astronomical Observatory, Ostervoldgade 3, DK-1350 Copenhagen, Denmark


Evolution of the coalescence rate of double neutron stars (NS) and neutron star - black hole (BH) binaries are computed for model galaxies with different star formation rates. Assuming gamma-ray bursts (GRB) to originate from NS+NS or NS+BH merging in distant galaxies, theoretical tex2html_wrap_inline175 - tex2html_wrap_inline177 distributions for gamma-ray bursts (GRB) are calculated for the first time taking the computed merging rates into account. We use a flat cosmological model ( tex2html_wrap_inline179 ) with different values of the cosmological constant tex2html_wrap_inline181 and under various assumptions about the star formation history in galaxies. The calculated source evolution predicts a 5-10 times increase of the source statistics at count rates 3-10 times lower than the exising BATSE sensitivity limit. The most important parameter in fitting the 2nd BATSE catalogue is the initial redshift of star formation, which is found to be tex2html_wrap_inline183 depending on a poorly determined average spectral index of GRB.

Mike E. Prokhorov
Tue Aug 20 18:36:42 MSD 1996