Exploring Short Gammaray Bursts as Gravitationalwave Standard Sirens
Abstract
Recent observations support the hypothesis that a large fraction of "shorthard" gammaray bursts (SHBs) are associated with the inspiral and merger of compact binaries. Since gravitationalwave (GW) measurements of welllocalized inspiraling binaries can measure absolute source distances, simultaneous observation of a binary's GWs and SHB would allow us to directly and independently determine both the binary's luminosity distance and its redshift. Such a "standard siren" (the GW analog of a standard candle) would provide an excellent probe of the nearby (z <~ 0.3) universe's expansion, independent of the cosmological distance ladder, thereby complementing other standard candles. Previous work explored this idea using a simplified formalism to study measurement by advanced GW detector networks, incorporating a high signaltonoise ratio limit to describe the probability distribution for measured parameters. In this paper, we eliminate this simplification, constructing distributions with a Markov Chain Monte Carlo technique. We assume that each SHB observation gives source sky position and time of coalescence, and we take nonspinning binary neutron star and black holeneutron star coalescences as plausible SHB progenitors. We examine how well parameters (particularly distance) can be measured from GW observations of SHBs by a range of groundbased detector networks. We find that earlier estimates overstate how well distances can be measured, even at fairly large signaltonoise ratio. The fundamental limitation to determining distance proves to be a degeneracy between distance and source inclination. Overcoming this limitation requires that we either break this degeneracy, or measure enough sources to broadly sample the inclination distribution.
 Publication:

The Astrophysical Journal
 Pub Date:
 December 2010
 DOI:
 10.1088/0004637X/725/1/496
 arXiv:
 arXiv:0904.1017
 Bibcode:
 2010ApJ...725..496N
 Keywords:

 cosmology: theory;
 distance scale;
 gammaray burst: general;
 gravitational waves;
 Astrophysics  Cosmology and Extragalactic Astrophysics;
 General Relativity and Quantum Cosmology
 EPrint:
 19 pages, 10 figures. Accepted for publication in ApJ