General relativistic simulations of blackholeneutronstar mergers: Effects of blackhole spin
Abstract
Blackholeneutronstar (BHNS) binary mergers are candidate engines for generating both shorthard gammaray bursts and detectable gravitational waves. Using our most recent conformal thinsandwich BHNS initial data and our fully general relativistic hydrodynamics code, which is now adaptive mesh refinement capable, we are able to efficiently and accurately simulate these binaries from large separations through inspiral, merger, and ringdown. We evolve the metric using the BaumgarteShapiroShibataNakamura formulation with the standard moving puncture gauge conditions, and handle the hydrodynamics with a highresolution shockcapturing scheme. We explore the effects of BH spin (aligned and antialigned with the orbital angular momentum) by evolving three sets of initial data with BH:NS mass ratio q=3: the data sets are nearly identical, except the BH spin is varied between a/M_{BH}=0.5 (antialigned), 0.0, and 0.75. The number of orbits before merger increases with a/M_{BH}, as expected. We also study the nonspinning BH case in more detail, varying q between 1, 3, and 5. We calculate gravitational waveforms for the cases we simulate and compare them to binary blackhole waveforms. Only a small disk (<0.01M_{⊙}) forms for the antialigned spin case (a/M_{BH}=0.5) and for the most extrememassratio case (q=5). By contrast, a massive (M_{disk}≈0.2M_{⊙}) hot disk forms in the rapidly spinning (a/M_{BH}=0.75) aligned BH case. Such a disk could drive a shorthard gammaray burst, possibly by, e.g., producing a copious flux of neutrinoantineutrino pairs.
 Publication:

Physical Review D
 Pub Date:
 February 2009
 DOI:
 10.1103/PhysRevD.79.044024
 arXiv:
 arXiv:0812.2245
 Bibcode:
 2009PhRvD..79d4024E
 Keywords:

 04.25.D;
 04.25.dk;
 04.30.w;
 Numerical relativity;
 Numerical studies of other relativistic binaries;
 Gravitational waves: theory;
 Astrophysics;
 General Relativity and Quantum Cosmology
 EPrint:
 28 pages, 24 figures, replaced with the published version, minor changes