Xi Serpentis

Xi Serpentis, Latinized from ξ Serpentis, is a triple star[10] system in the Serpens Cauda (tail) section of the equatorial constellation Serpens. Based upon an annual parallax shift of 30.98 mas as seen from Earth,[1] it is located 105.3 light years from the Sun. The star system is visible to the naked eye with a base apparent visual magnitude of +3.54.[2] It is moving closer to the Sun and will make perihelion passage at a distance of 27 ly (8.2 pc) in around 690,000 years.[12]

Xi Serpentis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Serpens
Right ascension  17h 37m 35.19983s[1]
Declination −15° 23′ 54.7940″[1]
Apparent magnitude (V) 3.54[2]
Characteristics
Spectral type A9 IIIp Sr[3]
U−B color index +0.12[2]
B−V color index +0.27[2]
Astrometry
Radial velocity (Rv)−42.8±0.7[4] km/s
Proper motion (μ) RA: −42.10[1] mas/yr
Dec.: −59.94[1] mas/yr
Parallax (π)30.98 ± 0.19[1] mas
Distance105.3 ± 0.6 ly
(32.3 ± 0.2 pc)
Absolute magnitude (MV)+1.00[5]
Orbit[6]
Period (P)2.2923 d
Eccentricity (e)0.00
Periastron epoch (T)2419210.191 JD
Semi-amplitude (K1)
(primary)		19.4 km/s
Details
ξ Ser Aa
Mass2.06[7] M☉
Luminosity30.6[8] L☉
Surface gravity (log g)3.55[3] cgs
Temperature7,217±41[7] K
Metallicity [Fe/H]+0.07[3] dex
Rotational velocity (v sin i)54[9] km/s
Age1.03[7] Gyr
ξ Ser Ab
Mass0.18[10] M☉
Other designations
ξ Ser, 55 Serpentis, BD−15° 4621, FK5 658, HD 159876, HIP 86263, HR 6561, SAO 160700[11]
Database references
SIMBADdata

The inner pair form a single-lined spectroscopic binary with an orbital period of 2.29 days following a circular orbit with an eccentricity of 0.00.[6] The primary, component Aa, has a visual magnitude of 3.54.[13] It is a white-hued G-type giant star with a stellar classification of A9 IIIp Sr.[3] This indicates it is a chemically peculiar Ap star with an abnormal abundance of strontium. The primary has around double[7] the mass of the Sun, while its close companion, component Ab,[13] has only 18%[10] of the Sun's mass.

The third member, component B, is a magnitude 13.0[13] common proper motion companion.[10] As of 2012, it was located at an angular separation of 24 arc seconds along a position angle of 78° from the inner pair.[13] It has about 27% of the Sun's mass and an estimated orbital period of 14,763 years.[10]

Name

In Chinese, Tiān Shì Zuǒ Yuán (天市左垣), meaning Left Wall of Heavenly Market Enclosure, refers to an asterism which is represent eleven old states (and region) in China which is marking the left borderline of the enclosure, consisting of ξ Serpentis, δ Herculis, λ Herculis, μ Herculis, ο Herculis, 112 Herculis, ζ Aquilae, η Serpentis, θ1 Serpentis, ν Ophiuchi and η Ophiuchi.[14] Consequently, the Chinese name for ξ Serpentis itself is Tiān Shì Zuǒ Yuán shí (天市左垣十, English: the Tenth Star of Left Wall of Heavenly Market Enclosure), representing the region of Nanhai (南海, lit. meaning southern sea)[15][16]

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References
  1. van Leeuwen, F. (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.
  2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
  3. Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637.
  4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  5. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  6. Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy and Astrophysics, 424 (2): 727, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213.
  7. Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 88, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88.
  8. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.
  9. Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393: 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943.
  10. Tokovinin, A.; et al. (May 2006), "Tertiary companions to close spectroscopic binaries", Astronomy and Astrophysics, 450 (2): 681–69, arXiv:astro-ph/0601518, Bibcode:2006A&A...450..681T, doi:10.1051/0004-6361:20054427.
  11. "ksi Ser". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-03-23.
  12. Bailer-Jones, C. A. L. (March 2015), "Close encounters of the stellar kind", Astronomy & Astrophysics, 575: 13, arXiv:1412.3648, Bibcode:2015A&A...575A..35B, doi:10.1051/0004-6361/201425221, A35.
  13. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122: 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
  14. (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  15. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 23 日
  16. (in Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name Archived August 10, 2010, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
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