Numerical Simulations of Compact Neutron Star Binary Mergers

Washington State University, Pullman WA

Investigators

Abstract

This award funds research into mergers of binary neutron stars and of binaries consisting of a neutron star and a black hole. These phenomena are among the primary sources of gravitational radiation for ground-based detectors such as the Laser Interferometer Gravitational Wave Observatory (LIGO), and they may explain the observed short-duration gamma ray bursts (GRBs). Computer models are needed both to calculate the expected gravitational waveforms for these mergers and also to test their viability as sources of GRBs. This project will carry out large-scale, detailed computer simulations of black hole-neutron star and neutron star-neutron star mergers, focusing on three main issues. First, it will study the evolution of the nuclear matter debris left around the post-merger black hole, especially the effects of magnetic fields and neutrino radiation that are expected to be critical in delivering energy to a GRB. Second, it will explore the variety of black hole-neutron star binaries by modeling currently unstudied extremes of black hole mass and spin. Third, it will characterize the effects of neutron star physics on the gravitational waveforms. Accurate gravitational waveform predictions will be crucial for detecting binary merger signals in LIGO data and for extracting information about the neutron star structure. Such information might be able to constrain unknown properties of nuclear matter. Numerical techniques developed for this project will be applicable to other problems in astrophysical fluid dynamics. Most of the funding from this award is used for student support. The PI directs both graduate and undergraduate students. These students receive valuable training in computer programming, numerical problem solving, and hydrodynamics, gaining important skills applicable to a broad range of technical fields. Results from this project will be used in communicating the excitement of astrophysics to the wider public.