The mass of the black hole in the low inclination LMXB transient system J0422+32 (= Nova Persei 1992)

Beekman, G., Shahbaz, T., Naylor, T., Charles, P.A., Wagner, R.M., and Martini, P. 1997, MNRAS, 290, 303

We present the first infrared light curve of GRO J0422+32, and use it 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 and 26 degrees, implying that the black hole mass is greater than ~ 15 Msun. Re-modelling the data with a 30 percent accretion disc contamination level changes the result little, the new limits being 13-31 degrees for the inclination, and greater than ~ 9Msun for the mass. Our results are the lowest inclination and, consequently, the highest mass claims yet made for this system. Previous observations of dips seen during outburst are suggestive of a partial eclips. Here we show that an eclipse interprestation of the so-caled orbital dips is inconsistent with other data; the "disps" are more likely to be random luminosity variations of a disc in outburst. We also show, for the first time, how an equation by King et al. (1996) allows a lower limit to the compact object mass in the SXTs to be independently estimated by use of the orbital period and spectral type only. This allows the spectroscopist to immediately identify the strong black hole candidates amongst SXTs with orbital periods <~ 2 days. These new mass estimates are in agreement with the ellipsoidally determined mass estimates, and indicate that GRS J0422+32 contains a black hole with a mass >~ 28 Msun.

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