Gravitational Wave Physics : Peter Meszaros

The the NSF Physics Frontier Center for Gravitational Wave Physics was established in 2000, incorporating members of the Physics and Astronomy & Astrophysics departments at Penn State, as well as a number of long-term senior visitors, postdoctoral fellows and graduate students. It runs an active conference and workshop program, dealing with numercial relativity, astrophysics of gravitational wave sources and gravitational wave detection techniques. My own emphasis here is gravitational astrophysics.

With Shiho Kobayashi, we have studied gravitational radiation from various proposed gamma-ray burst (GRB) progenitor models, in particular compact mergers and massive stellar collapses. These models have in common a high angular rotation rate, and the final stage involves a rotating black hole and accretion disk system. We consider the in-spiral, merger and ringing phases, and for massive collapses we consider the possible effects of asymmetric collapse and break-up, as well bar-mode instabilities in the disks. We calculate the strain and frequency of the gravitational waves expected from various progenitors, at distances based on occurrence rate estimates. Based on simplifying assumptions, we give estimates of the probability of detection of gravitational waves by the advanced LIGO system from the different GRB scenarios. For the NS-NS and NS-BH scenarios this is done assuming that wave templates will be available. If some fraction of GRBs are produced such coompact binary mergers, the gravitational wave chirp signal of the in-spiral phase should be detectable by the advanced LIGO within one year, associated with the GRB electromagnetic signal. For the BH-WD, BH-He and collapsar cases, where templates are likely to be uncertain at best, the signal/noise ratios are estimated using a cross-correlation technique with two co-aligned detectors. Under these assumptions, collapsar GRB models would be expected to be marginally detectable as gravitational wave sources by the advanced LIGO within one year of observations.

Another investigation with Shiho Kobayashi (2003) concerned the possible relation between polarized gravitational waves from GRB and their electromagnetic radiation, both of which should depend on angle in a predictable way. While measurements will require more advanced detectors, such relationships provide valuable constraints on the production mechanisms.

References

``Polarized Gravitational Waves from Gamma-Ray Bursts", Shiho Kobayashi and Peter Meszaros, 2002, ApJ(Lett.) in press (astro-ph/0212539)