Astronomy:Phi Virginis

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Short description: Binary star system in the constellation Virgo
φ Virginis
(incl. Elgafar)
Virgo constellation map.svg
Red circle.svg
Location of φ Virginis (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Virgo
Right ascension  14h 28m 12.13894s[1]
Declination −02° 13′ 40.6579″[1]
Apparent magnitude (V) +4.81[2]
Characteristics
Spectral type G2 IV[2]
B−V color index +0.683[3]
Astrometry
Radial velocity (Rv)−9.88±0.15[3] km/s
Proper motion (μ) RA: −139.53[1] mas/yr
Dec.: −4.04[1] mas/yr
Parallax (π)27.58 ± 1.01[1] mas
Distance118 ± 4 ly
(36 ± 1 pc)
Absolute magnitude (MV)1.68[4]
Details[3]
Mass1.80[5] M☉
Radius4 R☉
Luminosity12.6 L☉
Surface gravity (log g)3.4 cgs
Temperature5,534 K
Metallicity [Fe/H]−0.06 dex
Rotational velocity (v sin i)15.5 km/s
Age1.5[5] Gyr
Other designations
Elgafar, φ Vir, 105 Virginis, BD−01°2957, FK5 533, GJ 550.2, HD 126868, HIP 70755, HR 5409, SAO 139951[6]
Database references
SIMBADdata

Phi Virginis (φ Virginis, abbreviated Phi Vir, φ Vir) is a binary star[7] in the zodiac constellation of Virgo. It can be seen with the naked eye, having an apparent visual magnitude of +4.81.[2] Based upon parallax measurements obtained during the Hipparcos mission, it is located roughly 118 light-years (36 parsecs) distant from the Sun.[1]

The two components are designated Phi Virginis A (officially named Elgafar /ˈɛlɡəfɑːr/, the traditional name for the system)[8] and B.

Nomenclature

φ Virginis (Latinised to Phi Virginis) is the binary's Bayer designation. The designations of the two components as Phi Virginis A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[9]

Ideler described an Arabic lunar mansion "El-ġafr" (Arabic الغفر al-ghafr) for the stars Phi, Iota and Kappa Virginis.[10] In 2016, the IAU organized a Working Group on Star Names (WGSN)[11] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[12] It approved the name Elgafar for the component Phi Virginis A on 1 June 2018 and it is now so included in the List of IAU-approved Star Names.[8]

In Chinese, 亢宿 (Kàng Xiù), meaning Neck, refers to an asterism consisting of Phi Virginis, Kappa Virginis, Iota Virginis, and Lambda Virginis.[13] Consequently, Phi Virginis itself is known as 亢宿三 (Wěi Xiù sān), "the Third Star of Neck".[14]

Properties

The primary component, Phi Virginis A, has a stellar classification of G2 IV,[2] indicating that it is a G-type subgiant which is evolving away from the main sequence. It is slightly variable with an amplitude of 0m.06.[15] The star has about 1.8 times the mass of the Sun,[5] 4 times the Sun's radius, and shines with 12.6 times the luminosity of the Sun.[3] It is around 1.5[5] billion years old and is spinning with a projected rotational velocity of 15.5 km/s. The effective temperature of the star's outer atmosphere is 5,534 K.[3]

The secondary, Phi Virginis B, is a magnitude 9.10 companion at an angular separation of 5.160 arcseconds.[7] A second visual companion lies at an angular separation of 91.40 arcseconds along a position angle of 202°, as of 2000.[16]

The system is a source of X-ray emission with a luminosity of 2.158×1020 erg/s.[17]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 Gray, R. O. et al. (2001), "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars", The Astronomical Journal 121 (4): 2148–2158, doi:10.1086/319956, Bibcode: 2001AJ....121.2148G. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Massarotti, Alessandro et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal 135 (1): 209–231, doi:10.1088/0004-6256/135/1/209, Bibcode: 2008AJ....135..209M. 
  4. ↑ Schiavon, Ricardo P. (July 2007), "Population Synthesis in the Blue. IV. Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations", The Astrophysical Journal Supplement Series 171 (1): 146–205, doi:10.1086/511753, Bibcode: 2007ApJS..171..146S. 
  5. ↑ 5.0 5.1 5.2 5.3 Mallik, Sushma V.; Parthasarathy, M.; Pati, A. K. (October 2003), "Lithium and rotation in F and G dwarfs and subgiants", Astronomy and Astrophysics 409 (1): 251–261, doi:10.1051/0004-6361:20031084, Bibcode: 2003A&A...409..251M. 
  6. ↑ "* phi Vir". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+phi+Vir. 
  7. ↑ 7.0 7.1 Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  8. ↑ 8.0 8.1 "Naming Stars". IAU.org. https://www.iau.org/public/themes/naming_stars/. 
  9. ↑ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  10. ↑ Ideler, Ludwig (1809). Untersuchungen über den Ursprung und die Bedentung der Sternnamen. J. F. Weiss. https://archive.org/details/untersuchungenb01idelgoog. 
  11. ↑ "IAU Working Group on Star Names (WGSN)". https://www.iau.org/science/scientific_bodies/working_groups/280/. 
  12. ↑ "WG Triennial Report (2015-2018) - Star Names". p. 5. https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf. 
  13. ↑ (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.
  14. ↑ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 , Hong Kong Space Museum. Accessed on line November 23, 2010.
  15. ↑ Adelman, S. J. et al. (December 2000), "On the Variability of G0-G9 Stars", Information Bulletin on Variable Stars 4993: 1, Bibcode: 2000IBVS.4993....1A. 
  16. ↑ Mason, B. D. et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal 122 (6): 3466–3471, doi:10.1086/323920, Bibcode: 2001AJ....122.3466M, http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=B/wds, retrieved 2015-07-22. 
  17. ↑ Makarov, Valeri V. (October 2003), "The 100 Brightest X-Ray Stars within 50 Parsecs of the Sun", The Astronomical Journal 126 (4): 1996–2008, doi:10.1086/378164, Bibcode: 2003AJ....126.1996M. 



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