1999A&A...341..491H

Keck observations of the black-hole candidate GRO J0422+32 in quiescence have been used by Filippenko, Matheson, & Ho (1995ApJ...455..614F) to determine a mass function f(M_x)=1.21±0.06M_☉ for the compact object. Reanalysis of the data shows that the mass ratio, q=M_c/M_x, is q=0.116^+0.079_–0.071 from the rotational broadening of the companion star υsini=90⁺²²_–27km/s (1σ). From q and the mass function (slightly revised to 1.13±0.09M_☉), we derive the mass of the compact object, M_x=(1.4±0.2)sin^–3iM_☉. The companion star (M2⁺²_–1 spectral type) contributes 61±4% of the light at red wavelengths. An Hα Doppler image of the system shows the typical ring-like distribution of an accretion disk. Emissivity laws for Hα in black-hole binaries roughly follow an R^–1.5 law, which is also supported by GRO J0422+32. The Li I λ6708 absorption line is not detected (1σ equivalent width limit of 0.13Å), in contrast to four other X-ray binaries.