A0620-00
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Monoceros |
| Right ascension | 06h 22m 44.542s |
| Declination | −00° 20′ 44.29″ |
| Apparent magnitude (V) | 11.2 |
| Characteristics | |
| Evolutionary stage | Black hole + main sequence |
| Spectral type | K2 V |
| Variable type | X-ray nova, Ellipsoidal |
| Astrometry | |
| Radial velocity (Rv) | −5±12 km/s |
| Proper motion (μ) | RA: −0.439 mas/yr Dec.: −5.138 mas/yr |
| Parallax (π) | 0.6969±0.1168 mas |
| Distance | approx. 4,700 ly (approx. 1,400 pc) |
| Orbit | |
| Period (P) | 7.75234 ± 0.00010 hr |
| Inclination (i) | 50.98 ± 0.87° |
| Periastron epoch (T) | JD 2446082.7481 ± 0.0008 |
| Semi-amplitude (K1) (primary) | 457 ± 8 km/s |
| Details | |
| Black hole | |
| Mass | 5.86±1.24 M☉ |
| Star | |
| Mass | 0.34±0.03 M☉ |
| Radius | 1.057 R☉ |
| Luminosity | 0.44 L☉ |
| Surface gravity (log g) | 5.0 cgs |
| Temperature | 5,000 K |
| Metallicity [Fe/H] | 0.0 dex |
| Rotational velocity (v sin i) | 83.8±1.9 km/s |
| Other designations | |
| 1A 0620-00, INTREF 297, Nova Mon 1917, Nova Mon 1975, Mon X-1, V616 Mon | |
| Database references | |
| SIMBAD | data |
A0620-00 (abbreviated from 1A 0620-00) is a binary star system in the constellation of Monoceros, with an apparent magnitude of 11.2.
A0620-00 consists of two objects. The first object is a K-type main-sequence star. The second object cannot be seen, but based on its calculated mass of about 6 M☉, it is too massive to be a neutron star and must therefore be a stellar-mass black hole. The two objects orbit each other every 7.75 hours. At a distance of roughly 3,300 light-years (1,000 parsecs) away, the black hole of A0620-00 would be one of the nearest known black holes to the Solar System, closer than GRO J1655-40.
A0620-00 has undergone two X-ray outbreaks. The first one was in 1917. The second burst, in 1975, was detected by the Ariel 5 satellite. During that time, A0620-00 was the brightest X-ray point source. It is now classified as an X-ray nova. Its black hole nature was determined in 1986.
The black hole in A0620-00 pulls matter from the K-type star into an accretion disk. The accretion disk emits significant amounts of visible light and X-rays. Because the K-type star has been pulled into an ellipsoidal shape, the amount of surface area visible, and thus the apparent brightness, changes from the Earth's perspective. A0620-00 also bears the variable star designation V616 Monocerotis.