6 research outputs found
Hydrogen-Accreting Carbon-Oxygen White Dwarfs of Low Mass: Thermal and Chemical Behavior of Burning Shells
Numerical experiments have been performed to investigate the thermal behavior
of a cooled down white dwarf of initial mass M_{\rm WD} = 0.516 M_{\sun}
which accretes hydrogen-rich matter with Z = 0.02 at the rate
\msun \yrm1, typical for a recurrent hydrogen shell flash regime. The evolution
of the main physical quantities of a model during a pulse cycle is examined in
detail. From selected models in the mass range
\msunend, we derive the borders in the - plane of the
steady state accretion regime when hydrogen is burned at a constant rate as
rapidly as it is accreted. The physical properties during a hydrogen shell
flash in white dwarfs accreting hydrogen-rich matter with metallicities Z =
0.001 and Z = 0.0001 are also studied. For a fixed accretion rate, a decrease
in the metallicity of the accreted matter leads to an increase in the thickness
of the hydrogen-rich layer at outburst and a decrease in the hydrogen-burning
shell efficiency. In the - plane, the borders of the
steady state accretion band are critically dependent on the metallicity of the
accreted matter: on decreasing the metallicity, the band is shifted to lower
accretion rates and its width in is reduced.Comment: 31 pages and 10 Postscript figures; Accepted for publication on Ap
Distribution of compact object mergers around galaxies
Compact object mergers are one of the currently favored models for the origin
of GRBs. The discovery of optical afterglows and identification of the nearest,
presumably host, galaxies allows the analysis of the distribution of burst
sites with respect to these galaxies. Using a model of stellar binary evolution
we synthesize a population of compact binary systems which merge within the
Hubble time. We include the kicks in the supernovae explosions and calculate
orbits of these binaries in galactic gravitational potentials. We present the
resulting distribution of merger sites and discuss the results in the framework
of the observed GRB afterglows.Comment: 8 pages, 5 figures, submitted to MNRA