Short GRB and binary black hole standard sirens as a probe of dark energy

Observations of the gravitational radiation from well-localized, inspiralingcompact object binaries can measure absolute source distances with highaccuracy. When coupled with an independent determination of redshift through anelectromagnetic counterpart, these standard sirens can provide an excellentprobe of the expansion history of the Universe and the dark energy. Shortgamma-ray bursts, if produced by merging neutron star binaries, would bestandard sirens with known redshifts detectable by ground-based GW networkssuch as LIGO-II, Virgo, and AIGO. Depending upon the collimation of these GRBs,a single year of observation of their gravitational waves can measure theHubble constant to about 2%. When combined with measurement of the absolutedistance to the last scattering surface of the cosmic microwave background,this determines the dark energy equation of state parameter w to 9%. Similarly,supermassive binary black hole inspirals will be standard sirens detectable byLISA. Depending upon the precise redshift distribution, 100 sources couldmeasure w at the 4% level.Comment: 8 pages, submitted to PR