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Observation data
Epoch J2000      Equinox J2000
Constellation Monoceros
Right ascension 06h 22m 44.503s[1]
Declination −00° 20′ 44.72″[1]
Apparent magnitude (V) 11.2[1]
Spectral type K5 V + black hole[2]
Variable type X-ray nova, Ellipsoidal[3]
Radial velocity (Rv) −5 ± 12[4] km/s
Distance 3460 ± 390 ly
(1060 ± 120[2] pc)
Period (P) 7.75234 ± 0.00010[4] hr
Inclination (i) 50.98 ± 0.87[2]°
Periastron epoch (T) JD 2446082.7481 ± 0.0008[4]
Semi-amplitude (K1)
457 ± 8[4] km/s
Black hole
Mass 6.61 ± 0.25 M
K-type star
Mass 0.40 ± 0.045 M
Other designations
1A 0620-00, INTREF 297, Nova Mon 1917, Nova Mon 1975, Mon X-1, V616 Mon[1]
Database references

A0620-00 (abbreviated from 1A 0620-00) is a binary star system in the constellation of Monoceros.

A0620-00 consists of two objects. The first object is a K-type main-sequence star with a spectral type of K5 V.[2] The second object cannot be seen, but based on its calculated mass of 6.6 M,[2] it is too massive to be a neutron star and must therefore be a stellar-mass black hole.[4] At a distance of about roughly 3,300 light-years (1,000 parsecs) away, this would make A0620-00 the nearest black hole to the Solar System, closer than GRO J1655-40.[5] The two objects orbit each other every 7.75 hours.[4]

A0620-00 has undergone two X-ray outbreaks. The first one was in 1917.[6] The second time, in 1975, the burst was detected by the Ariel 5 satellite.[7] During that time, A0620-00 was the brightest X-ray point source.[4] It is now classified as an X-ray nova.[4]

The black hole in A0620-00 pulls matter from the K-type star into what is called an accretion disk.[2] 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.[3]

See also[edit]


  1. ^ a b c d "1A 0620-00". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 26 August 2017. 
  2. ^ a b c d e f g Cantrell, Andrew G.; Bailyn, Charles D.; Orosz, Jerome A.; McClintock, Jeffrey E.; Remillard, Ronald A.; Froning, Cynthia S.; Neilsen, Joseph; Gelino, Dawn M.; Gou, Lijun (2010). "The Inclination of the Soft X-Ray Transient A0620-00 and the Mass of its Black Hole". The Astrophysical Journal. 710 (2): 1127–1141. arXiv:1001.0261Freely accessible. Bibcode:2010ApJ...710.1127C. doi:10.1088/0004-637X/710/2/1127. 
  3. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S. 1. Bibcode:2009yCat....1.2025S. 
  4. ^ a b c d e f g h McClintock, J. E.; Remillard, R. A. (1986). "The black hole binary A0620-00". Astrophysical Journal. 308: 110–122. Bibcode:1986ApJ...308..110M. doi:10.1086/164482. 
  5. ^ Foellmi, Cédric (2009). "What is the closest black hole to the Sun?". New Astronomy. 14 (8): 674–691. arXiv:0812.4232Freely accessible. Bibcode:2009NewA...14..674F. doi:10.1016/j.newast.2009.04.003. 
  6. ^ Eachus, L. J.; Wright, E. L.; Liller, W. (1976). "Optical observations of the recurrent nova associated with A0620-00 - 1917-1975". Astrophysical Journal. 2. 203: L17–L19. Bibcode:1976ApJ...203L..17E. doi:10.1086/182009. 
  7. ^ Elvis, M.; Page, C. G.; Pounds, K. A.; Ricketts, M. J.; Turner, M. J. L. (1975). "Discovery of powerful transient X-ray source A0620-00 with Ariel V Sky Survey Experiment". Nature. 257: 656, 657. Bibcode:1975Natur.257..656E. doi:10.1038/257656a0. 

External links[edit]

  • "A0620-00". Black Hole Encyclopedia. StarDate. 12 February 2012.