The two components are designated Phi Virginis A (also named Elgafar[1]) 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).[2]Ideler described an Arabic lunar mansion "El-gafr" for the stars Phi, Iota and Kappa Virginis.[3] In 2016, the IAU organized a Working Group on Star Names (WGSN)[4] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[5] 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.[1]In Chinese, {{lang|zh|亢宿}} ({{lang|zh-Latn|Kàng Xiù}}), meaning Neck, refers to an asterism consisting of Phi Virginis, Kappa Virginis, Iota Virginis, and Lambda Virginis.[6] Consequently, Phi Virginis itself is known as {{lang|zh|亢宿三}} ({{lang|zh-Latn|Wěi Xiù sān}}), "the Third Star of Neck".[7]
Properties
The primary component, Phi Virginis A, has a stellar classification of G2 IV,[3] 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.[27] The star has about 1.8 times the mass of the Sun,[12] 4 times the Sun's radius, and shines with 12.6 times the luminosity of the Sun.[5] It is around 1.5[12] 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.[5]
The secondary, Phi Virginis B, is a magnitude 9.10 companion at an angular separation of 5.160 arcseconds.[15] A second visual companion lies at an angular separation of 91.40 arcseconds along a position angle of 202°, as of 2000.[33]
The system is a source of X-ray emission with a luminosity of {{Val|2.158e20|u=erg/s}}.[34]
References
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2. ^{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |date=2010 |eprint=1012.0707 |class=astro-ph.SR |last1= Hessman |first1=F. V. |last2= Dhillon |first2=V. S. |last3= Winget |first3=D. E. |last4= Schreiber |first4=M. R. |last5= Horne |first5=K. |last6= Marsh |first6=T. R. |last7= Guenther |first7=E. |last8= Schwope |first8=A. |last9= Heber |first9=U. }}
3. ^{{cite book |first=Ludwig |last=Ideler |title=Untersuchungen über den Ursprung und die Bedentung der Sternnamen |url=https://books.google.co.uk/books?id=gxLA4xSXWy8C&redir_esc=y |publisher=J. F. Weiss |date=1809 }}
4. ^{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|accessdate=22 May 2016}}
5. ^{{cite web | url=https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | page=5 | title=WG Triennial Report (2015-2018) - Star Names |accessdate=2018-07-14}}
6. ^{{zh icon}} 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}}.
7. ^{{zh icon}} 香港太空館 - 研究資源 - 亮星中英對照表 {{webarchive|url=https://web.archive.org/web/20081025110153/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm |date=2008-10-25 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.
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