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φ Virginis
(incl. Elgafar)
Location of φ Virginis (circled)
Observation data
Epoch J2000       Equinox J2000
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  mas [1]
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
SIMBAD data

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. ^ a b c d e f van Leeuwen, F. (November 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, S2CID  18759600.
  2. ^ a b c d 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, Bibcode: 2001AJ....121.2148G, doi: 10.1086/319956, S2CID  117076031.
  3. ^ a b c d e 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, Bibcode: 2008AJ....135..209M, doi: 10.1088/0004-6256/135/1/209.
  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, arXiv: astro-ph/0611464, Bibcode: 2007ApJS..171..146S, doi: 10.1086/511753, S2CID  13946698.
  5. ^ a b c d 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, Bibcode: 2003A&A...409..251M, doi: 10.1051/0004-6361:20031084.
  6. ^ "* phi Vir". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-09-18.
  7. ^ a b 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, arXiv: 0806.2878, Bibcode: 2008MNRAS.389..869E, doi: 10.1111/j.1365-2966.2008.13596.x, S2CID  14878976.
  8. ^ a b "Naming Stars". IAU.org. Retrieved 18 June 2018.
  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.
  11. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  12. ^ "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
  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 Archived 2008-10-25 at the Wayback Machine, 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, Bibcode: 2001AJ....122.3466M, doi: 10.1086/323920, 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, Bibcode: 2003AJ....126.1996M, doi: 10.1086/378164.
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