THE MASS OF THE BLACK-HOLE IN THE LOW-INCLINATION LMXB TRANSIENT SYSTEM GRO J0422-PERSEI-1992)(32 (=NOVA)

We present the first infrared light curve of GRO J0422 + 32, and use i t along with R-band data and published I- and Cousins R-c-band data to constrain the inclination of the system to be between 10 degrees and 26 degrees, implying that the black hole mass is greater than similar to 15M.. Remodelling the data with a 30 per cent accretion dise contam ination level changes the result little, the new limits being 13 degre es-31 degrees for the inclination, and greater than similar to 9 M. fo r the mass. Our results are the lowest inclination and, consequently, the highest mass claims yet made for this system. Previous observation s of dips seen during outburst are suggestive of a partial eclipse. He re we show that an eclipse interpretation of the so-called orbital dip s is inconsistent with other data; the 'dips' are more likely to be ra ndom luminosity variations of a disc in outburst. We also show, for th e first time, how an equation by King et al. allows a lower limit for the compact object mass in the soft X-ray transients (SXTs) to be inde pendently estimated by use of the orbital period and spectral type onl y. This allows the spectroscopist to identify immediately the strong b lack hole candidates amongst SXTs with orbital periods less than or si milar to 2 d. These new mass estimates are in agreement with the ellip soidally determined mass estimates, and indicate that GRO J0422 + 32 c ontains a black hole with a mass greater than or similar to 28 M..