This award will fund a new study to determine the masses of black holes in binary systems. Using the new NSF-funded infrared FIRE (Folded-port InfraRed Echellette) spectrograph at the Magellan Observatory in Chile, Dr. Remillard and his team will measure the radial velocities and rotational line-broadening for the companions to a number of black holes. Infrared observations are more useful than those at visible wavelengths, since there is much less extinction from dust and where the weakest companion stars radiate most strongly. The goals of the project are (1) to obtain new measurements of black hole masses; (2) to make mass measurements for accreting neutron stars; and (3) to conduct a long-term study of GRS 1915+105, which is unique for its variability, high luminosity, and productivity in producing jets.
Mass measurements anchor general efforts to infer black hole spin values via X-ray observations. Values of mass and spin are primary inputs for theorists working on stellar evolution of massive stars, supernovae, hypernovae, and binary evolution. Inferences of BH mass and spin will energize the general effort to develop quantitative applications of general relativity in the strong gravity regime.