On the Mass of the Black Hole in GS 2000+25

October 1996 • 1996ApJ...470L..57C

Authors • Callanan, Paul J. • Garcia, Michael R. • Filippenko, Alexei V. • McLean, Ian • Teplitz, Harry

Abstract • We present J- and K'-band (1.95--2.35 mu m) photometry of the quiescent X-ray nova GS 2000+25, obtained in an attempt to constrain the mass of the compact object (MX). Combined with the mass function of 4.97 Msolar, the infrared light curves imply MX <= 11 Msolar (90% confidence level), regardless of the evolutionary state of the secondary, for a mass ratio q of 4 < q < 30. For a secondary mass in the range M2 = 0.4--0.9 Msolar (as expected for a K dwarf companion), and assuming a negligible contribution from the disk at these wavelengths, we find MX = 8.5 +/- 1.5 Msolar and an inclination of 65 deg +/- 9 deg. The observed infrared color is consistent with that expected of a K dwarf secondary. If the accretion disk continuum is given by f lambda ~ lambda -1.8, as observed in other quiescent X-ray novae, we constrain the accretion disk contribution to the K' flux (independently of optical estimates) to <=12%.

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• PDF https://iopscience.iop.org/article/10.1086/310287/pdf
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