Scorpius X-1

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Scorpius X-1
Observation data
Epoch J2000.0        Equinox J2000.0
Constellation Scorpius
Right ascension 16h 19m 55.0693s [1]
Declination −15° 38′ 24.018″ [1]
Apparent magnitude  (V)12.40 [2]
Characteristics
Spectral type M4-M5V [3]
Variable type X-ray binary
Astrometry
Proper motion (μ)RA: −7.185 mas/yr [1]
Dec.: −12.332 mas/yr [1]
Parallax (π)0.4297±0.0220  mas [1]
Distance 7,600 ± 400  ly
(2,300 ± 100  pc)
Orbit [3]
Period (P)0.7873114(5) days
Semi-major axis (a)4.37  R☉
Inclination (i)25–34°
Semi-amplitude (K1)
(primary)		74.9±0.5 km/s
Details [3]
Optical star
Mass 0.40  M☉
Radius 1.25  R☉
Luminosity 0.114  L☉
Temperature 2,500–3,050  K
Neutron star
Mass 1.4  M☉
Radius 15–20  km
Temperature (3–5)×107  K
Other designations
V818 Sco, H 1620-15, RE J1619-153, XSS J16204-1536, 2U 1617-15, 4U 1617-15
Database references
SIMBAD data

Scorpius X-1 is a low-mass X-ray binary located roughly 9,000 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. [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. [5] 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 [6] or June 19, 1962, [7] [8] detected the first X-rays from another celestial source (Scorpius X-1) at J1950 RA 16h 15m Dec −15.2°. [6] The rocket was designed to observe X-rays from the moon rather than smaller, extrasolar sources, and therefore was unable to accurately retrieve the position and strength of the X-ray signal. The source was estimated to be at J1950 coordinates RA 16h 15m Dec −15.2°. [9]

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. [10]

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. [12] 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. [5] 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. [12]

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. [13] The origin of the system is a matter of debate. There is evidence that the two stars were not born together; studies based on the reconstruction of the orbit of Sco X-1 suggest that the binary may have been formed by a close encounter inside a globular cluster. However, it is not clear how to reconcile this formation scenario with the circularisation of the binary's orbit. [14]

See also

References

  1. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  2. ↑ Liu, Q. Z.; Paradijs, J. van; Heuvel, E. P. J. van den (2007-07-01). "A catalogue of low-mass X-ray binaries in the Galaxy, LMC, and SMC (Fourth edition)". Astronomy & Astrophysics. 469 (2): 807–810. arXiv: 0707.0544 . Bibcode:2007A&A...469..807L. doi:10.1051/0004-6361:20077303. ISSN   0004-6361.
  3. 1 2 3 Cherepashchuk, A M; Khruzina, T S; Bogomazov, A I (2021-10-05). "Parameters of the X-ray binary system Scorpius X-1". Monthly Notices of the Royal Astronomical Society. 508 (1): 1389–1403. arXiv: 2109.00967 . doi: 10.1093/mnras/stab2515 . ISSN   0035-8711.
  4. ↑ 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 .
  5. 1 2 Shklovskii, Iosif S. (1978). Stars: Their Birth, Life, and Death . W.H. Freeman. ISBN   978-0-7167-0024-1.
  6. 1 2 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 .
  7. ↑ Drake SA (September 2006). "A Brief History of High-Energy Astronomy: 1960–1964".
  8. ↑ "Chronology—Quarter 2 1962". Archived from the original on 2010-01-18.
  9. ↑ 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. 23. International Astronomical Union: 227–39. Bibcode:1965IAUS...23..227B.
  10. ↑ 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.
  11. ↑ 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 .
  12. 1 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 .
  13. ↑ 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.
  14. ↑ 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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