NOAO >   Observing Info >   Approved Programs >   2002B-0297

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Proposal Information for 2002B-0297


PI: Dawn M. Gelino, University of California, San Diego, dgelino@ucsd.edu
Address: 9500 Gilman Drive, La Jolla, CA 92093-0424

Title: Measuring the Mass of the Black Hole in J1118+480

Abstract: Soft x-ray transients (SXTs) are systems that suddenly brighten at x- ray and optical wavelengths. Their outbursts last several months, and peak at luminosities of ~10^38 erg s^-1. The primary object is believed to be a black hole, but only a handful of such objects have been rigorously confirmed. To determine the mass of the primary object we need to measure the orbital inclination. We propose to determine the orbital inclination for the high Galactic latitude SXT system J1118+480 through modeling of its infrared ellipsoidal variations. Because SXTs are not eclipsing, modeling their light curves is the \it only feasible method for determining the inclination. We will model the light curves with the most recent version of the Wilson-Devinney code (WD98). The multi-wavelength light curves that we obtain in this project are needed to confidently determine system parameters, account for any other sources of light in the system, and explore the nature of the secondary stars. Using the derived orbital inclination angle, we can determine the primary mass of the SXT to better understand how the primary mass influences the outburst behavior. We have successfully used NOAO facilities and this modeling technique to find accurate black hole masses in four SXTs. In order to expand the sample of known black hole systems and further investigate the nature of their secondary stars, we request two nights with SQIID on the KPNO 2.1m to obtain simultaneous J, H, and K-band light curves of J1118+480 and the prototype SXT, A0620-00.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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