Scorpius X-1

Last updated
V818 Sco or Scorpius X-1
Observation data
Epoch J2000.0        Equinox J2000.0
Constellation Scorpius
Right ascension 16h 19m 55.07s [1]
Declination −15° 38' 24.8" [1]
Apparent magnitude  (V)12.2 [1]
Distance 9,000  ly
(2,800 [2]   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 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]

Contents

Discovery and early study

The possible existence of cosmic soft X-rays was first proposed by Bruno Rossi, MIT Professor and Board Chairman of American Science and Engineering in Cambridge, Massachusetts to Martin Annis, President of AS&E. Following his urging, the company obtained a contract from the United States Air Force to explore the lunar surface prior to the launch of astronauts to the Moon, and incidentally to perhaps see galactic sources of X-rays.

Subsequently, Scorpius X-1 was discovered in 1962 by a team, under Riccardo Giacconi, who launched an Aerobee 150 sounding rocket carrying a highly sensitive soft X-ray detector designed by Frank Paolini. The rocket trajectory was slightly off course but still detected a significant emission of soft X-rays that were not coming from the Moon. Thus fortuitously, and as first pointed out by Frank Paolini, Scorpius X-1 became the first X-ray source discovered outside the Solar System. The angular resolution of the detector did not initially allow the position of Scorpius X-1 to be accurately determined. This led to suggestions that the source might be located near the Galactic Center, but it was eventually realized that it lies in the constellation Scorpius. [4] As the first discovered X-ray source in Scorpius, it received the designation Scorpius X-1.

The Aerobee 150 rocket launched on June 12, 1962, detected the first X-rays from another celestial source (Scorpius X-1) at J1950 RA 16h 15m Dec −15.2°. [5] Sco X-1 is a LMXB in which the visual counterpart is V818 Scorpii.

Although the above reference indicates the rocket launch was on June 12, 1962, other sources indicate the actual launch was at 06:59:00 UTC on June 19, 1962. [6] [7]

Historical footnote: "The instrumentation had been designed for an attempt to observe X-rays from the moon and was not equipped with collimation to restrict the field of view narrowly. As a result, the signal was very broad, and accurate definition of the size and position of the source was not possible. A similar experiment was repeated in October 1962 when the Galactic Center was below the horizon and the strong source was not present. A third attempt, in June 1963, verified the results of the June 1962 flight." [8] The Galactic Center is < 20° RA and < 20° Dec from Sco X-1, the two X-ray sources are separated by ~20° of arc and may not have been resolvable in the June 1962 flight. [8]

Scorpius XR-1 has been observed at J1950 RA 16h 15m Dec −15.2°. [8]

In 1967 (before the discovery of pulsars), Iosif Shklovsky examined X-ray and optical observations of Scorpius X-1 and correctly concluded that the radiation comes from a neutron star accreting matter from a companion. [9]

Characteristics

A broadband optical light curve for V818 Scorpii, adapted from Hynes et al. (2016) V818ScoLightCurve.png
A broadband optical light curve for V818 Scorpii, adapted from Hynes et al. (2016)

Its X-ray output is 2.3×1031 W, about 60,000 times the total luminosity of the Sun. [2] Scorpius X-1 shows regular variations of up to 1 magnitude in its intensity, with a period of around 18.9 hours. The source varies irregularly in optical wavelengths as well, but these changes are not correlated with the X-ray variations. [4] Scorpius X-1 itself is a neutron star whose intense gravity draws material off its companion into an accretion disk, where it ultimately falls onto the surface, releasing a tremendous amount of energy. As this stellar material accelerates in Scorpius X-1's gravitational field, X-rays are emitted. The measured luminosity for Scorpius X-1 is consistent with a neutron star which is accreting matter at its Eddington limit. [2]

This system is classified as a low-mass X-ray binary; the neutron star is roughly 1.4 solar masses, while the donor star is only 0.42 solar masses. [11] The two stars were probably not born together; recent research suggests that the binary may have been formed by a close encounter inside a globular cluster. [12]

See also

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<span class="mw-page-title-main">Iosif Shklovsky</span> Soviet astronomer (1916–1985)

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<span class="mw-page-title-main">Lambda Scorpii</span> Triple star system in the constellation Scorpius

Lambda Scorpii is a triple star system and the second-brightest object in the constellation of Scorpius. It is formally named Shaula; Lambda Scorpii is its Bayer designation, which is Latinised from λ Scorpii and abbreviated Lambda Sco or λ Sco. With an apparent visual magnitude of 1.62, it is one of the brightest stars in the night sky.

<span class="mw-page-title-main">Centaurus X-3</span> Binary star with an X-ray pulsar in the constellation Centaurus

Centaurus X-3 is an X-ray pulsar with a period of 4.84 seconds. It was the first X-ray pulsar to be discovered, and the third X-ray source to be discovered in the constellation Centaurus. The system consists of a neutron star orbiting a massive, O-type supergiant star dubbed Krzeminski's star after its discoverer, Wojciech Krzemiński. Matter is being accreted from the star onto the neutron star, resulting in X-ray emission.

<span class="mw-page-title-main">Tau Scorpii</span> Star in the constellation of Scorpius

Tau Scorpii, Latinized from τ Scorpii, formally known as Paikauhale, is a star in the southern zodiac constellation of Scorpius. The apparent visual magnitude of Tau Scorpii is +2.8, while parallax measurements yield a distance estimate of roughly 470 light-years (150 parsecs) from Earth.

ω1 Scorpii, Latinised as Omega1 Scorpii, is a star in the zodiac constellation of Scorpius. With an apparent visual magnitude of 3.95 it can be seen with the naked eye, 0.22 degree north of the ecliptic. Parallax measurements of this star give an estimated distance of around 470 light years from the Sun. It is a member of the Scorpius–Centaurus association.

<span class="mw-page-title-main">NGC 6231</span> Open Cluster in the constellation of Scorpius

NGC 6231 is an open cluster in the southern sky located half a degrees north of Zeta Scorpii. NGC 6231 is part of a swath of young, bluish stars in the constellation Scorpius known as the Scorpius OB1 association. The star Zeta1 is a member of this association, while its brighter apparent partner, Zeta2, is only 150 ly from Earth and so is not a member.

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<span class="mw-page-title-main">Remo Ruffini</span>

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<span class="mw-page-title-main">Astrophysical X-ray source</span> Astronomical object emitting X-rays

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<span class="mw-page-title-main">History of X-ray astronomy</span>

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Zeta<sup>1</sup> Scorpii Star in the constellation Scorpius.

Zeta1 Scorpii is a B-type hypergiant star in the constellation of Scorpius. It has an apparent visual magnitude which varies between 4.66 and 4.86. It is a member of the Scorpius OB1 association, and the open star cluster NGC 6231, also known as the "Northern jewel box" cluster. Around 36 times as massive as the Sun, it is also one of the most luminous stars known in the Galaxy, with an estimated bolometric luminosity of around 850,000 times that of the Sun and a radius 103 times that of the Sun.

<span class="mw-page-title-main">U Scorpii</span> Recurrent nova system first seen in 1863

U Scorpii is a recurrent nova system; one of 10 known recurring novae in the Milky Way galaxy. Located near the northern edge of the constellation Scorpius it normally has a magnitude of 18, but reaches a magnitude of about 8 during outbursts. Outbursts have been observed in 1863, 1906, 1936, 1979, 1987, 1999, 2010, and 2022.

12 Scorpii is a probable triple star system in the zodiac constellation of Scorpius, located about 300 light years away from the Sun. It has the Bayer designation c1 Scorpii; 12 Scorpii is the Flamsteed designation. This system is faintly visible to the naked eye with a combined apparent visual magnitude of 5.67. It is a probable member of the Sco OB2 moving group.

2 Scorpii (A Scorpii) is a double star in the southern zodiac constellation of Scorpius. The brighter component has an apparent visual magnitude of 4.69, which is bright enough to be visible to the naked eye, while the fainter star is of magnitude 6.98. The distance to this pair can be estimated from the annual parallax shift of 6.49±0.51 mas, which places it roughly 500 light years away. It has a peculiar velocity of 16.5±2.4 km/s and is moving closer to the Sun with a heliocentric radial velocity of about −9 km/s, which will bring it to a perihelion distance of 450 ly (139 pc) in about 2.9 million years. This is a probable (73% chance) member of the Lower Centaurus–Crux group of the nearby Scorpius–Centaurus association (Sco OB2), or else (27% chance) it is a member of the Gould's Belt.

<span class="mw-page-title-main">N Scorpii</span> Star in the constellation of Scorpius

N Scorpii, also known as HD 148703, is a solitary, bluish-white hued star located in the southern constellation Scorpius. It has an apparent magnitude of 4.23, making it readily visible to the naked eye. N Scorpii was initially given the Bayer designation Alpha Normae by Lacaille but it was later moved from Norma to Scorpius. N Scorpii is currently located 550 light years away based on parallax measurements from the Hipparcos satellite and is part of the Upper Scorpius–Centaurus region of the Scorpius–Centaurus association.

<span class="mw-page-title-main">V1073 Scorpii</span> Variable star in the constellation Scorpius

V1073 Scorpii is a variable star in the constellation Scorpius. It has a non-Greek Bayer designation of k Scorpii. The star has a blue-white hue and is visible to the naked eye with an apparent visual magnitude that fluctuates around +4.87. Parallax measurements yield a distance estimate of approximately 2,920 ly (896 pc) from the Sun, and it is drifting further away with a radial velocity of +7 km/s. It has an absolute magnitude of −6.8

References

  1. 1 2 3 Staff (March 3, 2003). "V* V1357 Cyg—High Mass X-ray Binary". Centre de Données astronomiques de Strasbourg. Retrieved 2009-12-21.
  2. 1 2 3 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 .
  4. 1 2 3 Shklovskii, Iosif S. (1978). Stars: Their Birth, Life, and Death . W.H. Freeman. ISBN   978-0-7167-0024-1.
  5. ↑ Giacconi R (August 2003). "Nobel Lecture: The dawn of X-ray astronomy". Rev. Mod. Phys. 75 (3): 995–1010. Bibcode:2003RvMP...75..995G. doi: 10.1103/RevModPhys.75.995 .
  6. ↑ Drake SA (September 2006). "A Brief History of High-Energy Astronomy: 1960–1964".
  7. ↑ "Chronology—Quarter 2 1962". Archived from the original on 2010-01-18.
  8. 1 2 3 Bowyer S; Byram ET; Chubb TA; Friedman H (1965). Steinberg JL (ed.). "Observational results of X-ray astronomy". Astronomical Observations from Space Vehicles, Proceedings from Symposium No. 23 Held in Liège, Belgium, 17 to 20 August 1964. International Astronomical Union. 23: 227–39. Bibcode:1965IAUS...23..227B.
  9. ↑ Shklovsky, I.S. (April 1967). "On the Nature of the Source of X-Ray Emission of SCO XR-1". Astrophys. J. 148 (1): L1–L4. Bibcode:1967ApJ...148L...1S. doi:10.1086/180001.
  10. ↑ Hynes, Robert I.; Schaefer, Bradley E.; Baum, Zachary A.; Hsu, Ching-Cheng; Cherry, Michael L.; Scaringi, Simone (July 2016). "Kepler K2 observations of Sco X-1: orbital modulations and correlations with Fermi GBM and MAXI". Monthly Notices of the Royal Astronomical Society. 459 (4): 3596–3613. arXiv: 1605.00546 . Bibcode:2016MNRAS.459.3596H. doi: 10.1093/mnras/stw854 .
  11. ↑ Steeghs, D.; Casares, J. (2002). "The Mass Donor of Scorpius X-1 Revealed". The Astrophysical Journal. 568 (1): 273–278. arXiv: astro-ph/0107343 . Bibcode:2002ApJ...568..273S. doi:10.1086/339224. S2CID   14136652.
  12. ↑ Mirabel, I. F.; Rodrogues, I. (2003). "The origin of Scorpius X-1". Astronomy and Astrophysics. 398 (3): L25–L28. arXiv: astro-ph/0301580 . Bibcode:2003A&A...398L..25M. doi:10.1051/0004-6361:20021767. S2CID   2585509.
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