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]
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| 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]](http://upload.wikimedia.org/wikipedia/commons/thumb/e/e1/V518PerLightCurve.png/220px-V518PerLightCurve.png)
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.
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