Epoch J2000.0 Equinox J2000.0
|Right ascension||20h 24m 03.83s|
|Declination||+33° 52′ 02.2″|
|Apparent magnitude (V)||11.2 - 18.8|
|Spectral type||K3 III|
|U−B color index||+0.3|
|B−V color index||+1.5|
|Absolute magnitude (MV)||+3.4|
|A (black hole)|
|Surface gravity (log g)||3.50 cgs|
|Rotational velocity (v sin i)||36.4 km/s|
V404 Cygni is a microquasar and a binary system consisting of a black hole with a mass of about ±3 solar masses12 and a late G or early K companion star of mass slightly smaller than the Sun in the constellation of Cygnus. The star and the black hole orbit each other every 29 d at fairly close range. Due to their proximity the 6.471main sequence star would be distorted into egg shape by the black hole's gravity and lose mass to the black hole. The "V" in the name indicates that it is a variable star, which repeatedly gets brighter and fainter over time. It is also considered a nova, because at least three times in the 20th century it produced a bright outburst of energy. Finally, it is a soft X-ray transient because it periodically emits short bursts of X-rays.
In 2009, the black hole in the V404 Cygni system became the first black hole to have an accurate parallax measurement for its distance from the Solar System. Measured by very-long-baseline interferometry using the High Sensitivity Array, the distance is ±0.14 kiloparsecs, 2.39 or ±0.46)×103 (7.80light-years.
On May 22, 1989 the Japanese Ginga Team discovered a new X-ray source that was cataloged as GS 2023+338. This source was subsequently identified as coincident in position with a previously known nova cataloged as V404 Cygni.
On 15 June 2015 NASA's Swift satellite detected the first signs of renewed activity. A worldwide observing campaign was commenced and on 17 June ESA's INTEGRAL Gamma-ray observatory started monitoring the outburst. INTEGRAL has been detecting "repeated bright flashes of light time scales shorter than an hour, something rarely seen in other black hole systems", and during these flashes V404 Cygni is the brightest object in the X-ray sky - up to fifty times brighter than the Crab Nebula. This outburst is the first since 1989. Other outbursts occurred in 1938 and 1956, and the outbursts are probably caused by material piling up in a disk around the black hole until a tipping point is reached. The outburst was unusual in that physical processes in the inner accretion disk were detectable in optical photometry from small telescopes; previously, these variations were thought to be detectable with space-based X-ray telescopes only. A detailed analysis of the INTEGRAL data revealed the existence of so-called pair plasma near the black hole. This plasma consists of electrons and their antimatter counterparts, positrons.
- Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E. L.; Kirkpatrick, J. D.; Light, R. M.; Marsh, K. A.; McCallon, H.; Schneider, S.; Stiening, R.; Sykes, M.; Weinberg, M.; Wheaton, W. A.; Wheelock, S.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". VizieR On-line Data Catalog: II/246. Originally published in: 2003yCat.2246....0C. 2246. Bibcode:2003yCat.2246....0C.
- Watson, C. L. (2006). "The International Variable Star Index (VSX)". The Society for Astronomical Sciences 25th Annual Symposium on Telescope Science. Held May 23-25. 25: 47. Bibcode:2006SASS...25...47W.
- Khargharia, Juthika; Froning, Cynthia S.; Robinson, Edward L. (2010). "Near-infrared Spectroscopy of Low-mass X-ray Binaries: Accretion Disk Contamination and Compact Object Mass Determination in V404 Cyg and Cen X-4". The Astrophysical Journal. 716 (2): 1105. arXiv:. Bibcode:2010ApJ...716.1105K. doi:10.1088/0004-637X/716/2/1105.
- Liu, Q. Z.; Van Paradijs, J.; Van Den Heuvel, E. P. J. (2007). "A catalogue of low-mass X-ray binaries in the Galaxy, LMC, and SMC (Fourth edition)". Astronomy and Astrophysics. 469 (2): 807. Bibcode:2007A&A...469..807L. doi:10.1051/0004-6361:20077303.
- 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....102025S.
- Bernardini, F.; Russell, D. M.; Shaw, A. W.; Lewis, F.; Charles, P. A.; Koljonen, K. I. I.; Lasota, J. P.; Casares, J. (2016). "Events leading up to the 2015 June Outburst of V404 Cyg". The Astrophysical Journal Letters. 818: L5. arXiv:. Bibcode:2016ApJ...818L...5B. doi:10.3847/2041-8205/818/1/L5.
- Shahbaz, T.; Ringwald, F. A.; Bunn, J. C.; Naylor, T.; Charles, P. A.; Casares, J. (1994). "The mass of the black hole in V404 Cygni". Monthly Notices of the Royal Astronomical Society. 271: L10. Bibcode:1994MNRAS.271L..10S. doi:10.1093/mnras/271.1.L10.
- González Hernández, Jonay I.; Casares, Jorge; Rebolo, Rafael; Israelian, Garik; Filippenko, Alexei V.; Chornock, Ryan (2011). "Chemical Abundances of the Secondary Star in the Black Hole X-Ray Binary V404 Cygni". The Astrophysical Journal. 738: 95. Bibcode:2011ApJ...738...95G. doi:10.1088/0004-637X/738/1/95.
- Shahbaz, T.; Ringwald, F. A.; Bunn, J. C.; Naylor, T.; et al. (1994). "The mass of the black hole in V404 Cygni". MNRAS. 271: L1–L14. Bibcode:1994MNRAS.271L..10S. doi:10.1093/mnras/271.1.10L (inactive 2016-07-05).
- Kimura, Mariko; et al. (7 January 2016). "Repetitive patterns in rapid optical variations in the nearby black-hole binary V404 Cygni". Nature. 529 (7584): 54–70. Bibcode:2016Natur.529...54K. doi:10.1038/nature16452.
- Miller-Jones, J. A. C.; Jonker; Dhawan (2009). "The first accurate parallax distance to a black hole". The Astrophysical Journal Letters. 706 (2): L230. arXiv:. Bibcode:2009ApJ...706L.230M. doi:10.1088/0004-637X/706/2/L230.
- R. M. Wagner; S. Starrfield; A. Cassatella; R. Gonzalez-Riestra; T. J. Kreidl; S. B. Howell; R. M. Hjellming; X. -H. Han; G. Sonneborn (24 July 2005). "The 1989 outburst of V404 cygni: A very unusual x-ray nova". Lecture Notes in Physics. Lecture Notes in Physics. 369: 429–430. doi:10.1007/3-540-53500-4_162. ISBN 978-3-540-53500-3.
- "Monster Black Hole Wakes Up After 26 Years". integral. ESA. Archived from the original on 26 June 2015. Retrieved 26 June 2015.
- "Gamma rays reveal pair plasma from a flaring black hole binary system". Max Planck Institute for Astrophysics. 29 February 2016.