December 5 – D. Gelino, UCSD  : Title "Determining the Masses of Compact Objects in Low-Mass X-Ray Binaries"

Abstract: Low mass x-ray binaries (LMXBs) contain compact, black hole or neutron star primaries, and cool, low-mass secondary stars. Since a limited number of black holes and neutron stars have accurate mass measurements, it is important to determine the primary masses of the LMXBs to better define the black hole and neutron star mass distributions, and to better constrain the neutron star equations of state. In order to determine the mass of a primary object, we need to know the orbital inclination of the system. We find the inclination through modeling of infrared ellipsoidal variations from the Roche lobe-filling secondary star. I will discuss our results for a few LMXBs, including the first black hole that appears to conclusively fall in the 3 - 5 solar mass range.