PI: Dawn M. Gelino, University of California, San Diego, firstname.lastname@example.org
Address: Center for Astrophysics and Space Sciences 0424, 9500 Gilman Drive, La Jolla, CA 92093-0424
CoI: John A. Tomsick, University of California, San Diego
CoI: William Heindl, University of California, San Diego
CoI: Philip Kaaret, Harvard-Smithsonian Center for Astrophysics
Title: Measuring Low Mass X-Ray Binary Compact Object Masses: 4U 0042+32 and XTE J2123-058
Abstract: Low mass x-ray binaries (LMXBs) contain compact, black hole (BH) or neutron star (NS) primaries, and cool, low-mass secondary stars. A limited number of BHs and NSs have accurate mass measurements. It is important to determine the primary mass of the LMXBs to better define the BH and NS mass distributions, and to better constrain the NS equations of state. To determine the mass of the primary object we need to measure the orbital inclination, i. We propose to not only confirm the identity of the optical counterpart for a BHC LMXB, 4U 0042+32, but also determine which of its two candidate orbital periods is correct, as well as determine its inclination the nature of its compact object. We will also determine i for a NS LMXB, J2123-058. Both inclinations will be found through modeling of infrared ellipsoidal variations. Because most LMXBs are not eclipsing, modeling their light curves is currently the \it only feasible method for determining the inclination. We will model the light curves with the WD98 modeling program. We have successfully used NOAO facilities and this modeling technique to find accurate BH masses in five LMXBs. In order to expand the sample of known BH and NS systems, we request four nights on the KPNO 4m to obtain infrared data on 4U 0042+32 and XTE J2123-058.
National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360