Scorpius X-1

V818 Sco or Scorpius X-1
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Scorpius
Right ascension	16h 19m 55.07s
Declination	−15° 38' 24.8"
Apparent magnitude (V)	12.2
Distance	9,000 ly; (2,800 pc)
Other designations
	V818 Sco, H 1620-15, 2RE J161955-153824, 1XRS 16170-155, 2A 1616-155, INTEGRAL1 21, RE J1619-153, XSS J16204-1536, 3A 1617-155, INTREF 685, RE J161956-153814, X Sco X-1, 2EUVE J1619-15.6, KOHX 20, SBC7 569, EUVE J1619-15.6, 1M 1617-155, 2U 1617-15, AAVSO 1614-15, 1H 1617-155, 2MASS J16195506-1538250, 3U 1617-15, H 1617-155, 2RE J1619-153, 4U 1617-15
Database references
SIMBAD	data

Scorpius X-1 is an X-ray source located roughly 9000 light years away in the constellation Scorpius. Scorpius X-1 was the first extrasolar X-ray source discovered, and, aside from the Sun, it is the strongest apparent non-transient source of X-rays in the sky.^[3] The X-ray flux varies day-to-day, and is associated with an optically visible star, V818 Scorpii, that has an apparent magnitude which fluctuates between 12-13.^[4]

^ ^a ^b ^c Staff (March 3, 2003). "V* V1357 Cyg—High Mass X-ray Binary". Centre de Données astronomiques de Strasbourg. Retrieved 2009-12-21.
^ Bradshaw, C.F.; Fomalont, E.B.; Geldzahler, B.J. (1999). "High-Resolution Parallax measurements of Scorpius X-1". The Astrophysical Journal. 512 (2): L121–L124. Bibcode:1999ApJ...512L.121B. doi:10.1086/311889.
^ Giacconi, R.; Gursky, H.; Paolini, F.R.; Rossi, B.B. (1962). "Evidence for X-rays from sources outside the solar system". Phys. Rev. Lett. 9 (11): 439–443. Bibcode:1962PhRvL...9..439G. doi:10.1103/PhysRevLett.9.439.
^ Shklovskii, Iosif S. (1978). Stars: Their Birth, Life, and Death. W.H. Freeman. ISBN 978-0-7167-0024-1.

[simbad-1] Staff (March 3, 2003). "V* V1357 Cyg—High Mass X-ray Binary". Centre de Données astronomiques de Strasbourg. Retrieved 2009-12-21.

[par-2] Bradshaw, C.F.; Fomalont, E.B.; Geldzahler, B.J. (1999). "High-Resolution Parallax measurements of Scorpius X-1". The Astrophysical Journal. 512 (2): L121–L124. Bibcode:1999ApJ...512L.121B. doi:10.1086/311889.

[3] Giacconi, R.; Gursky, H.; Paolini, F.R.; Rossi, B.B. (1962). "Evidence for X-rays from sources outside the solar system". Phys. Rev. Lett. 9 (11): 439–443. Bibcode:1962PhRvL...9..439G. doi:10.1103/PhysRevLett.9.439.

[shklovskii-4] Shklovskii, Iosif S. (1978). Stars: Their Birth, Life, and Death. W.H. Freeman. ISBN 978-0-7167-0024-1.

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