Black Hole Spin Evolution: Implications for Short-hard Gamma Ray Bursts and Gravitational Wave Detection

astro-ph/0703131 [abs, ps, pdf, other] :

Title: Black Hole Spin Evolution: Implications for Short-hard Gamma Ray Bursts
and Gravitational Wave Detection


Authors:
Krzysztof Belczynski,
Ronald E. Taam,
Emmanouela Rantsiou,
Marc van der Sluys


Comments: 19 pages, 3 tables, 10 figures: submitted to ApJ

The evolution of the spin and tilt of black holes in compact black hole -
neutron star and black hole - black hole binary systems is investigated via the
population synthesis method. Based on recent results on accretion at super
Eddington rates in slim disk models, estimates of natal kicks, and the results
regarding fallback in supernova models, we obtain the black hole spin and
misalignment. It is found that the spin parameter, a_spin, is less than 0.5 for
initially non rotating black holes and the tilt, i_tilt, is less than 40 deg
for 50% of the systems in black hole - neutron star binaries. Upon comparison
with the results of black hole - neutron star merger calculations we estimate
that only a small fraction (~0.02) of these systems can potentially produce a
short-hard gamma ray burst. Only for high initial black hole spin parameters
(a_spin can this fraction be significant (~0.35). For the majority of
black holes in black hole - neutron star systems the spin magnitude is
increased to a_spin and the degree of spin misalignment (i_tilt ~ 40 deg)
is sufficiently high that the predicted gravitational radiation signal
significantly differs from that for non rotating black holes. However, due to
the (i) insensitivity of signal detection techniques to the black hole spin and
the (ii) predicted overall low contribution of black hole binaries to the
signal we find that the detection of gravitational waves are not greatly
inhibited by current searches with non spinning templates. It is pointed out
that the detection of a black hole - black hole binary inspiral system with
LIGO or VIRGO may provide a direct measurement of the initial spin of a black
hole.

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