Bibcode
Sigurdsson, Steinn; Pols, Onno R.; Bloom, Joshua S.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 305, Issue 4, pp. 763-769.
Advertised on:
5
1999
Citations
206
Refereed citations
169
Description
We find the distribution of coalescence times, birth rates, spatial
velocities, and subsequent radial offsets of coalescing neutron stars
(NSs) in various galactic potentials accounting for large asymmetric
kicks introduced during a supernova. The birth rates of bound NS-NS
binaries are quite sensitive to the magnitude of the kick velocities but
are, nevertheless, similar (~ 10 per galaxy per Myr) to previous
population synthesis studies. The distribution of merger times since
zero-age main sequence is, however, relatively insensitive to the choice
of kick velocities. With a median merger time of ~ 10^8 yr, we find that
compact binaries should closely trace the star formation rate in the
Universe. In a range of plausible galactic potentials (with
M_galaxy3x10^10 M_solar) the median radial offset of a NS-NS merger is
less than 10 kpc. At a redshift of z=1 (with H_0=65 km s^-1 Mpc^-1 and
Omega=0.2), this means that half the coalescences should occur within
~1.3 arcsec from the host galaxy. In all but the most shallow
potentials, 90 per cent of NS-NS binaries merge within 30 kpc of the
host. We find that although the spatial distribution of coalescing
neutron star binaries is consistent with the close spatial association
of known optical afterglows of gamma-ray bursts (GRBs) with faint
galaxies, a non-negligible fraction (~15 per cent) of GRBs should occur
well outside (30 kpc) dwarf galaxy hosts. Extinction owing to dust in
the host, projection of offsets, and a range in interstellar medium
densities confound the true distribution of NS-NS mergers around
galaxies with an observable set of optical transients/galaxy offsets.