The Laser Interferometer Gravitational-wave Observatory (LIGO) is on the brink of making the first direct detections of gravitational waves. With the improved sensitivity of Advanced LIGO, we expect to enter an era of astronomy in which frequent gravitational-wave measurements are used to learn about astrophysical sources. The inspiral and merger of binary neutron stars is a likely source for many gravitational-wave observations, and waveform models for the inspiral of such systems can be used to detect the signals using matched filtering. However, additional physics near merger is not captured by detection templates. As the stars coalesce, the gravitational waveforms will depend additionally on the properties of matter in the core of the stars. The relevant behavior is encoded in the equation of state of dense matter. Its effects on gravitational waveforms have not yet been fully modeled; while ever-improving analytic models in the inspiral and numerical simulations of the merger each contribute information, a complete picture remains elusive. This award supports a program of research by the PI and her students at California State University Fullerton (CSUF) to understand the effects of neutron-star matter on inspiral and merger, both by constructing hybrid (analytical-numerical) waveforms with explicit error estimates and by developing phenomenological waveforms which incorporate tidal resonance effects. The results will be incorporated into the public LIGO Algorithm Library for use in realistic search and parameter-estimation studies with the full data analysis infrastructure.
The proposed research is essential to maximize the astrophysical return on NSF's investment in LIGO. Improved understanding of measurement potential will inform configuration decisions as Advanced LIGO develops. Gravitational-wave measurements of neutron-star matter effects will potentially shine new light on the equation of state of matter above nuclear density, which is currently uncertain and a key research topic in both nuclear physics and astrophysics. This proposal also supports active involvement by undergraduate and masters students in the Physics program at CSUF, a primarily undergraduate Hispanic-serving institution with strong integration of teaching and research. Including students in cutting-edge research introduces them to the gravitational-wave science community, kindles future participation in science, and develops broadly applicable skills. The PI is actively involved in LIGO outreach, and will engage students, the University, and the surrounding community in the excitement of this new field of astronomy.