Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||20h 32m 25.78s|
|Declination||+40° 57′ 27.9″|
|Apparent magnitude (H)||13.192|
|Apparent magnitude (J)||15.309|
|Apparent magnitude (K)||11.921|
Cygnus X-3 is one of the stronger binary X-ray sources in the sky. Classified as a microquasar, it is believed to be a compact object in a binary system which is pulling in a stream of gas from an ordinary star companion. It is observed in X rays, gamma rays, infrared, and radio, with an orbital periodicity of approximately 4.8 h, among the shortest known at the time of its discovery.
Although it is only the third brightest X-ray source in the constellation Cygnus, after the more famous Cygnus X-1, it is located about 37,000 light-years away. It is heavily obscured by intervening interstellar gas and dust near the galactic plane, and fainter than 23rd magnitude in the optical, but is easily observable in the J, H, & K near-infrared bands.
Taking its distance and extinction into account, it appears to be one of the two or three most intrinsically luminous objects in the Galaxy.
It has also received attention because it is one of the few sources of ultra-high-energy cosmic rays, with energies in the 100 - 1000 TeV range. Its most unusual aspect is the production of anomalous cosmic ray events in a proton decay detector deep in Minnesota's Soudan iron mine. These events have defied analysis and have led to questions about whether Cygnus X-3 is a standard neutron star or perhaps something more exotic, like a star made of quarks.
Cygnus X-3 has distinguished itself by its intense X-ray emissions and by ultra-high energy cosmic rays. It also made astronomical headlines by a radio frequency outburst in September 1972 which increased its radio frequency emissions a thousandfold. Since then it has had periodic radio outbursts with a regular period of 367 days. These flares are of unknown origin, but they are exceedingly violent events. Naval Research Laboratory observations in October 1982 using the Very Large Array detected the shock wave from a flare; it was expanding at roughly one-third the speed of light.
Cygnus X-3 has an orbital period about its companion of only 4.79 hours. Intriguing underground events in the SOUDAN experiment in October 1985 included 60 anomalous muon events in a 3° cone around Cygnus X-3 with a precise period of 4.79 hours. If the association with Cygnus X-3 is confirmed, these events must either be due to neutrinos or some other very low-rest-mass, high-energy neutral particle of unknown nature, yet capable of producing muons via secondary interactions.
Infrequent gamma ray flares from Cygnus X-3 with energies around 100 MeV were detected in 2009 by the Fermi Gamma-ray Space Telescope and by the AGILE satellite. The intensity of these gamma ray outbursts varies at the same 4.8-hour orbital rate as the X-ray emissions, and they occur a few days before the onset of extremely energetic radio jets.
Cygnus X-3 is considered a high-mass X-ray binary (HMXB), because V1521 Cyg is a high-mass star.
- V* V1521 Cyg -- High Mass X-ray Binary, database entry, SIMBAD. Accessed on line November 7, 2008.
- Tavani, M. et al. (2009-12-03). "Extreme particle acceleration in the microquasar Cygnus X-3". Nature 462 (7273): 620–623. arXiv:0910.5344. Bibcode:2009Natur.462..620T. doi:10.1038/nature08578. PMID 19935645.
- Becklin, E. E.; Neugebauer, G.; Hawkins, F. J.; Mason, K. O.; Sanford, P. W.; Matthews, K.; Wynn-Williams, C. G. (1973). "Infrared and X-ray Variability of Cyg X-3". Nature 245 (5424): 302–304. Bibcode:1973Natur.245..302B. doi:10.1038/245302a0.
- Astronomers look to quark stars for a fifth dimension - fundamentals - 23 June 2007 - New Scientist