Iota Virginis

Iota Virginis (ι Virginis, abbreviated Iota Vir, ι Vir) is a binary star in the constellation of Virgo. Its apparent magnitude is 4.08.[2] Based on its parallax, it is assumed to be relatively nearby, at 72.5 light-years (22.24 parsecs).[1]

ι Virginis
(incl. Syrma)
Location of ι Virginis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Virgo
Right ascension  14h 16m 00.86951s[1]
Declination −06° 00′ 01.9633″[1]
Apparent magnitude (V) 4.08[2]
Characteristics
Spectral type F7IV-V[3]
U−B color index +0.02[4]
B−V color index +0.52[4]
Astrometry
Radial velocity (Rv)12.51 ± 0.18[5] km/s
Proper motion (μ) RA: -26.31[1] mas/yr
Dec.: -419.38[1] mas/yr
Parallax (π)44.97 ± 0.19[1] mas
Distance72.5 ± 0.3 ly
(22.24 ± 0.09 pc)
Absolute magnitude (MV)2.4[3]
Orbit[3]
Period (P)55 yr
Semi-major axis (a)0.830 ± 0.020″
Eccentricity (e)0.1 ± 0.2
Inclination (i)60 ± 9°
Longitude of the node (Ω)3 ± 20°
Periastron epoch (T)1950.7 ± 2.7
Argument of periastron (ω)
(secondary)		336 ± 27°
Details
ι Vir A
Mass1.5 ± 0.05[3] M☉
Radius2.5[6] R☉
Luminosity8.7[6] L☉
Surface gravity (log g)3.94[7] cgs
Temperature6282[7] K
Metallicity [Fe/H]−0.11[7] dex
Rotational velocity (v sin i)16[3] km/s
ι Vir B
Mass0.6 ± 0.2[3] M☉
Other designations
Syrma, 99 Vir, BD−05°3843, FK5 525, GJ 9473, HD 124850, HIP 69701, HR 5338, SAO 139824
Database references
SIMBADdata

Its two components are designated Iota Virginis A (officially named Syrma /ˈsɜːrmə/,[8] the traditional name for the system)[9] and B.

Nomenclature

ι Virginis (Latinised to Iota Virginis) is the system's Bayer designation. The designations of the two components as Iota 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).[10]

It bore the traditional name Syrma, derived from the Arabic سرما (تطريز sirmā "train (of a garment)".[11] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[12][13] to catalogue and standardize proper names for stars. The WGSN approved the name Syrma for Iota Virginis on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[9] For such names relating to members of multiple star systems, and where a component letter (from e.g. Washington Double Star Catalog) is not explicitly listed, the WGSN says that the name should be understood to be attributed to the brightest component by visual brightness.[14]

In China, 亢宿 (Kàng Xiù), meaning Neck, refers to an asterism consisting of this star, Kappa Virginis, Phi Virginis and Lambda Virginis.[15] Consequently, Iota Virginis itself is known as 亢宿二 (Kàngxiùèr, English: the Second Star of Neck).

Properties

Iota Virginis is an astrometric binary. The secondary regularly perturbs the primary, causing the latter to wobble around its barycenter.[3] A preliminary orbit with a period of 55 years has been calculated.[3]

Iota Virginis A is a yellow-colored star with a spectral class of F7IV-V. This star has 1.5 times the mass of the Sun, with a projected rotational velocity of 16 km s−1.[3] It is radiating 8.7 times the luminosity of the Sun[6] from its outer atmosphere at an effective temperature of 6,282 K.[7] The radius is about 2.5 times that of the Sun.[6]

Iota Virginis B has not been directly detected, but based on its mass (0.6 M☉) it may be a main-sequence star or a white dwarf.[3] That star is also responsible for the drifting radial velocity of the primary.[16]

In 2011, it was noticed that the faint K-type main-sequence star HD 125354 had a similar proper motion throughout space, and was likely physically associated.[17] Another 2015 paper supported this hypothesis. The star, which is located 1.2 ly (0.37 pc) away from Iota Virginis, also has a similar distance from the Sun, within the margin of error. It itself is a close binary with another star separated 0.33″ from the main star.[18]

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References
  1. 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.
  2. Gray, R. O.; Napier, M. G.; Winkler, L. I. (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. Bibcode:2001AJ....121.2148G. doi:10.1086/319956.
  3. Gontcharov, G.A.; Kiyaeva, O.V. (2010). "Photocentric orbits from a direct combination of ground-based astrometry with Hipparcos II. Preliminary orbits for six astrometric binaries". New Astronomy. 15 (3): 324. arXiv:1606.08182. Bibcode:2010NewA...15..324G. doi:10.1016/j.newast.2009.09.006.
  4. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  5. Maldonado, J.; Martínez-Arnáiz, R. M.; Eiroa, C.; Montes, D.; Montesinos, B. (2010). "A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups". Astronomy and Astrophysics. 521: A12. arXiv:1007.1132. Bibcode:2010A&A...521A..12M. doi:10.1051/0004-6361/201014948.
  6. Malagnini, M. L.; Morossi, C. (November 1990). "Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars". Astronomy and Astrophysics Supplement Series. 85 (3): 1015–1019. Bibcode:1990A&AS...85.1015M.
  7. Mallik, Sushma V. (December 1999). "Lithium abundance and mass". Astronomy and Astrophysics. 352: 495–507. Bibcode:1999A&A...352..495M.
  8. "syrma". Oxford English Dictionary (3rd ed.). Oxford University Press. September 2005. (Subscription or UK public library membership required.)
  9. "Naming Stars". IAU.org. Retrieved 16 December 2017.
  10. 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].
  11. Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. pp. 472. ISBN 0-486-21079-0.
  12. IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  13. IAU Formally Approves 227 Star Names, International Astronomical Union, retrieved 24 November 2016.
  14. "Bulletin of the IAU Working Group on Star Names, No. 2" (PDF). Retrieved 16 December 2017.
  15. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 28 日
  16. Borgniet, S.; Lagrange, A.-M.; Meunier, N.; Galland, F. (2017). "Extrasolar planets and brown dwarfs around AF-type stars". Astronomy & Astrophysics. 599: A57. arXiv:1608.08257. Bibcode:2017A&A...599A..57B. doi:10.1051/0004-6361/201628805.
  17. Shaya, Ed J.; Olling, Rob P. (January 2011). "Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue". The Astrophysical Journal Supplement. 192 (1): 2. arXiv:1007.0425. Bibcode:2011ApJS..192....2S. doi:10.1088/0067-0049/192/1/2.
  18. Fuhrmann, K.; Chini, R. (2015). "Multiplicity Among F-Type Stars. II". The Astrophysical Journal. 809: 107. Bibcode:2015ApJ...809..107F. doi:10.1088/0004-637X/809/1/107.
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