Workshop on Astrophysical Sources

of Gravitational Radiation

for Ground-Based Detectors

Joan Centrella, Drexel University joan@sparrow.drexel.edu 1

As the $21^{\rm st}$ century begins, gravitational wave astronomy is poised for unprecedented expansion and discovery. Understanding the expected gravitational wave frequencies and other characteristics of astrophysical sources is essential to take full advantage of these opportunities, and to stimulate and influence detector development. To this end, gravitational wave experimentalists, relativists, astronomers, and astrophysicists met at Drexel University on October 30 - November 1, 2000 for a workshop focusing on gravitational wave sources for ground-based detectors.

The scientific sessions began with a series of talks on the detectors. Barry Barish presented a review of first generation interferometers. He was followed by Peter Fritschel, who described the current plans for LIGO-II, and Kip Thorne, who discussed issues involving thermal noise, optical noise, and quantum non-demolition for instruments beyond LIGO-II. Bill Hamilton then gave an overview of resonant bar detectors and the international bar detector community.

The data expected from the LIGO-I science run was addressed by Albert Lazzarini, who also discussed the GriPhyN project and its relevance to LIGO data. Patrick Brady discussed LIGO data analysis efforts, and Sam Finn followed with a description of LIGO's science reach.

New initiatives in astronomy and astrophysics provide rich resources and partnerships for gravitational wave astronomy. Tom Gaisser reported on the recommendations of the Particle, Nuclear, and Gravitational Wave Astrophysics panel from the recently completed decadal survey Astronomy and Astrophysics in the New Millennium (see, e.g., http://www.nap.edu/books/0309070317/html/ ). He was followed by Tom Prince, who described the space-based LISA detector, and Bob Hanisch, who discussed the National Virtual Observatory; both of these projects received strong support from the decadal survey. Nick White gave an overview of NASA's future programs in high energy astrophysics, many of which focus on black holes and their environments.

Coalescing compact binaries constitute the ``bread and butter'' source for ground-based interferometers, and were addressed from a variety of directions. Vicky Kalogera began with a discussion of event rates for binary inspiral; she was followed by Steve McMillan, who described the formation of black hole binaries in globular clusters. The importance of large scale numerical simulations was highlighted by numerous speakers. Josh Faber and Fred Rasio presented new work on the hydrodynamics of neutron star mergers, and Max Ruffert underscored the importance of coalescing compact binaries for understanding gamma ray bursts. William Lee presented simulations of black hole-neutron star coalescence, and Richard Matzner discussed binary black hole collisions. Thomas Baumgarte concluded this session with a talk on the innermost stable circular orbit in compact binary systems.

Cosmological sources of stochastic gravitational waves were addressed by Arthur Kosowsky. David Spergel spoke on plans to use the CMB as a gravitational wave detector.

Stellar core collapse has long been proposed as a source of gravitational waves, and was discussed by Chris Fryer. Kimberly New described dynamical rotational instabilities that can arise in centrifugally hung compact cores, and David Brown discussed their occurrence during collapse. Gravitational radiation from secular bar-mode instabilities was addressed by Dong Lai.

In recent years, a number of exciting new developments have arisen in the study of rotating neutron stars. Jean Swank discussed X-ray observations of accretion instabilities on long and short timescales in low mass X-ray binaries. Tod Strohmayer described X-ray observations giving evidence for millisecond spins. Gravitational radiation produced by temperature gradients, and its importance for LIGO-II, was addressed by Lars Bildsten. Greg Ushomirsky discussed gravitational waves from r-modes in accreting neutron stars and young neutron stars.

Conference rapporteurs Rainer Weiss, Peter Saulson, and Joel Tohline provided thought-provoking and insightful overviews of the meeting.

This workshop proved to be a fruitful and enjoyable time for these different communities to interact with each other. Those who were unable to attend in person should visit http://www.physics.drexel.edu/events/astro_conference. At this website the transparencies of the talks can be viewed by going to the meeting program, and clicking on the title of each talk.



Jorge Pullin
2001-02-11