Keck observations of the black-hole candidate GRO J0422+32 ?

Keck observations of the black-hole candidate GRO J0422+32 in quiescence have been used by Filippenko, Matheson, & Ho (1995) to determine a mass functionf(Mx )= 1:21 0:06 M for the compact object. Reanalysis of the data shows that the mass ratio, q = Mc=Mx ,i sq =0 :116 +0:079 0:071 from the rotational broadening of the companion star sin i = 90 +22 27 km s 1 (1). From q and the mass function (slightly re- vised to 1:13 0:09 M), we derive the mass of the compact object, Mx =( 1:4 0:2) sin 3 iM . The companion star (M2 +2 1 spectral type) contributes 61 4% of the light at red wavelengths. An H Doppler image of the system shows the typical ring-like distribution of an accretion disk. Emissivity laws for H in black-hole binaries roughly follow an R 1:5 law, which is also supported by GRO J0422+32. The Li I 6708 absorption line is not detected (1 equivalent width limit of 0.13 ˚ A), in contrast to four other X-ray binaries.