GRO J0422+32 is an X-ray nova and black hole candidate that was discovered by the BATSE instrument on the CGRO satellite on 5 August 1992. During outburst, it was observed to be stronger than the Crab Nebula gamma-ray source out to photon energies of about 500 keV.
The mass of the black hole in GRO J0422+32 falls in the range 3.66 to 4.97 solar masses. This is the smallest yet found for any black hole, and near the theoretical upper mass limit (~2.7 solar masses) for a neutron star. Further analysis in 2012 calculated a mass of 2.1 solar masses, which raises questions as to what the object actually is.
Position (J2000) is RA 04 h 21 m 42.77 s +32 deg 54' 26.7".
It is identified with an M1V variable star, V518 Per, in the constellation Perseus, with magnitudes 13.5 in the B spectral band, and 13.2 in V.