1995A&A...293L..69B

We report on spectroscopic observations of the X-ray nova GRO J0422+32 obtained on February 4th 1994 when the source has just returned to a quiescence phase after successive outbursts. Optical spectra recorded in the range (3500-10500A) when the source was at magnitude V∼20.5, show features typical of the X-ray transients in quiescence. The Balmer lines are observed as strong very broad emission lines and the HeII(4686A) excitation line has disappeared. The Hα line shows a variable double-peak profile with a width suggesting a system inclined at i∼50deg. The peak separation and velocity changes of the lines are used to constrain the compact star mass. Assuming a 5.1h orbital period, an upper limit of Mc=<2.2M_☉ is derived for the mass of the compact star. This is still therefore consistent with a neutron star and does not seem to confirm the suggestion that GRO J0422+32 may harbour a black hole.