Swift Pointing and the Association Between Gamma-Ray Bursts and Gravitational-Wave Bursts

The currently accepted model for gamma-ray burst phenomena involves the violent formation of a rapidly rotating solar mass black hole. Gravitational waves should be associated with the black-hole formation, and their detection would permit this model to be tested, the black hole progenitor (e.g., coalescing binary or collapsing stellar core) identified, and the origin of the gamma rays (within the expanding relativistic fireball or at the point of impact on the interstellar medium) located. Even upper limits on the gravitational-wave strength associated with gamma-ray bursts could constrain the gamma-ray burst model. To do any of these requires joint observations of gamma-ray burst events with gravitational and gamma-ray detectors. Here we examine how the quality of an upper limit on the gravitational-wave strength associated with gammaray burst observations depends on the relative orientation of the gamma-ray-burst and gravitational-wave detectors, and apply our results to the particular case of the Swift Burst-Alert Telescope (BAT) and the LIGO gravitational-wave detectors. A result of this investigation is a science-based “figure of merit” that can be used, together with other mission constraints, to optimize the pointing of the Swift telescope for the detection of gravitational waves associated with gamma-ray bursts. Also Center for Gravitational Physics and Geometry, Department of Physics, and Department of Astronomy and Astrophysics; e-mail: [email protected] Also Center for Gravitational Physics and Geometry and Department of Physics; e-mail: [email protected] Also Center for Gravitational Wave Phenomenology and Center for Gravitational Physics and Geometry, Pennsylvania State University, University Park, PA-16801, USA; e-mail: [email protected] LIGO-P030074-00-Z