GRO J0422+32

GRO J0422+32^[1] is an X-ray nova and black hole candidate that was discovered by the BATSE instrument on the Compton Gamma Ray Observatory satellite on 5 August 1992.^[4][5] During outburst, it was observed to be stronger than the Crab Nebula gamma-ray source out to photon energies of about 500 keV.^[2]

GRO J0422+32

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Perseus
Right ascension	04h 21m 42.77s[1]
Declination	+32° 54′ 26.7″[1]
Apparent magnitude (V)	13.2
Distance	7,800[2] ly (2,400 pc)
Spectral type	M4.5V[1] + Black hole
Other designations
V518 Per, GRO J0422+33, RLC2006 XB2, Granat 0417+335, Nova Persei 1992, Nova Persei 1993, ZGH2005 OS00676-097731 GRO J0422+32, ZGH2005 XS00676B3-003
Database references
SIMBAD	data

A visual band light curve for GRO J0422+32, adapted from Chevalier and Ilovaiski (1995)^[3]

The mass of the black hole in GRO J0422+32 falls in the range 3.66 to 4.97 solar masses.^[6] This is the smallest yet found for any stellar black hole, and near the theoretical upper mass limit (~2.7 M_☉) for a neutron star. Further analysis in 2012 calculated a mass of 2.1 M_☉, which raises questions as to what the object actually is.^[7]

It is also known to have a companion M-type main-sequence star, V518 Per,^[8] in the constellation Perseus. It has a magnitude of 13.5 in the B spectral band, and 13.2 in the visible band.

See also

• List of nearest black holes