Xi Scorpii

Xi Scorpii (ξ Sco) is a quintuple star system in the constellation Scorpius. It was assigned this designation by Bayer, although Ptolemy had catalogued the star in Libra. Flamsteed assigned it the designation 51 Librae, but this has fallen out of use since modern constellation boundaries assign the star to Scorpius.[13]

Xi Scorpii
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
ξ Sco ABC
Right ascension  16h 04m 22.191s[1]
Declination −11° 22′ 22.60″[1]
Apparent magnitude (V) 4.17[2]
(5.16 / 4.87 / 7.30)[3]
ξ Sco D
Right ascension  16h 04m 25.9261s[4]
Declination −11° 26′ 57.778″[4]
Apparent magnitude (V) 7.43[5]
ξ Sco E
Right ascension  16h 04m 26.7184s[4]
Declination −11° 26′ 59.543″[4]
Apparent magnitude (V) 7.81[6]
Characteristics
ξ Sco ABC
Spectral type F4(V) + F6(V) + G1V[7]
U−B color index +0.00[8]
B−V color index +0.45[8]
ξ Sco DE
Spectral type K1(V) + K1(V)[9]
U−B color index +0.315[8]
B−V color index +0.75[8]
Astrometry
ξ Sco ABC
Radial velocity (Rv)-36.33 ± 0.83[10] km/s
Proper motion (μ) RA: -63.2[1] mas/yr
Dec.: -27.0[1] mas/yr
ξ Sco D
Radial velocity (Rv)-31.60 ± 0.2[11] km/s
Proper motion (μ) RA: -63.43[12] mas/yr
Dec.: -20.55[12] mas/yr
Parallax (π)35.90 ± 0.23[4] mas
Distance90.9 ± 0.6 ly
(27.9 ± 0.2 pc)
Orbit[3]
Primaryξ Sco A
Companionξ Sco B
Period (P)45.90 ± 0.60 yr
Semi-major axis (a)0.654 ± 0.006″
Eccentricity (e)0.744 ± 0.001
Inclination (i)34.5 ± 1.0°
Longitude of the node (Ω)25.3 ± 4.0°
Periastron epoch (T)B 1997.22 ± 0.02
Argument of periastron (ω)
(secondary)		163.8 ± 5.0°
Orbit[3]
Primaryξ Sco AB
Companionξ Sco C
Period (P)1514.43 yr
Semi-major axis (a)7.755″
Eccentricity (e)0.041
Inclination (i)131.5°
Longitude of the node (Ω)47.4°
Periastron epoch (T)B 2226.10
Argument of periastron (ω)
(secondary)		59.3°
Other designations
ξ Sco, BD−10° 4237 (only ABC), GJ 9540 (only ABC), HIP 78727 (only ABC), SAO 159665 (only AB), ADS 9909 (only ABC)
ξ Sco A: HD 144070, HR 5978, ADS 9909 A
ξ Sco B: HD 144069, HR 5977, ADS 9909 B
ξ Sco C: SAO 159666, ADS 9909 C
ξ Sco D: BD−11° 4057, GJ 9541 A, HD 144087, HIP 78738, SAO 159668, ADS 9910 A
Database references
SIMBADξ Sco ABC
ξ Sco AB
ξ Sco A
ξ Sco B
ξ Sco C
ξ Sco D
ξ Sco E
ARICNSξ Sco A
ξ Sco B
ξ Sco C

Nomenclature

ξ Scorpii (Latinized to Xi Scorpii) is the star's Bayer designation. Xi Scorpii has no proper name, though it was erroneously known as Graffias before that name was applied to Beta Scorpii.[14] Its Flamsteed designation is 51 Librae.[13] When the modern constellation boundaries were drawn, Xi Scorpii was assigned to Scorpius, and the Flamsteed designation fell out of use.

The five stars of Xi Scorpii all have different designations. Depending on the catalogue, however, some designations apply to more than one stars. Xi Scorpii A, B, and C appear very close together in the sky and are often given one designation, while D and E are sometimes also given a single designation. Struve's catalogue of multiple stars includes the pair AB and C as Σ1998[15] and the pair D and E as Σ1999.[16]

ComponentHRHDSAOHIPGJ
ξ Scorpii A5978144070159665787279540
ξ Scorpii B5977144069
ξ Scorpii Cnonenone159666
ξ Scorpii Dnone144087159668787389541
ξ Scorpii Enone14408815967078739

Properties

The Xi Scorpii system consists of five stars in two groups separated by about 4.7 arcminutes (or 0.08°) on the sky.[17]

The brighter group contains Xi Scorpii A, B, and C. A and B are both yellow-white F-type stars. A is slightly brighter and warmer.[7] They are separated by 0.744 arcseconds on average, and orbit around a common center once every 45.9 years.[3] The dimmer, seventh-magnitude Xi Scorpii C orbits this pair at about ten times the distance, having a separation of around 7.6 arcseconds.[3]

The second group contains Xi Scorpii D and E. Both D and E are K-type main-sequence stars, which are separated by about 11.9 arcseconds. They are known to be associated to each other and with the rest of the stars, because all stars share similar proper motions.[17]

A sixth component, the 11th-magnitude Xi Scorpii F, is located 81 arcseconds from D, but is not known to be gravitationally bound to the other five components. Therefore, it is not considered to be part of the system.

References
  1. Roeser, S.; Bastian, U. (1988). "A new star catalogue of SAO type". Astronomy and Astrophysics Supplement Series. 74: 449–451. Bibcode:1988A&AS...74..449R.
  2. "* ksi Sco". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2 August 2017.
  3. "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Retrieved 2 July 2017.
  4. Gaia Collaboration (2016). "Gaia Data Release 1". Astronomy & Astrophysics. 595: A2. arXiv:1609.04172. Bibcode:2016A&A...595A...2G. doi:10.1051/0004-6361/201629512.
  5. "HD 144087". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2 August 2017.
  6. "HD 144088". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2 August 2017.
  7. Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications". VizieR On-line Data Catalog. 1. Bibcode:2014yCat....1.2023S.
  8. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  9. Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars, Vol. 5". Michigan Spectral Survey. 5: 0. Bibcode:1999MSS...C05....0H.
  10. Tokovinin, A. A.; Smekhov, M. G. (2002). "Statistics of spectroscopic sub-systems in visual multiple stars" (PDF). Astronomy & Astrophysics. 382: 118. Bibcode:2002A&A...382..118T. doi:10.1051/0004-6361:20011586.
  11. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  12. van Leeuwen, F.; et al. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  13. Wagman, M. (August 1987). "Flamsteed's Missing Stars". Journal for the History of Astronomy. 18 (3): 209. Bibcode:1987JHA....18..209W. doi:10.1177/002182868701800305.
  14. Allen, R. H. (1899). Star-names and Their Meanings. New York: G. E. Stechert. p. 371.
  15. "** STF 1998". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 14 October 2017.
  16. "** STF 1999AB". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 14 October 2017.
  17. Tokovinin, A. A. (1997). "MSC - a catalogue of physical multiple stars". Astronomy and Astrophysics Supplement Series. 124: 75. Bibcode:1997A&AS..124...75T. doi:10.1051/aas:1997181. Archived from the original on 2017-06-20.
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