Eta Lyrae

Eta Lyrae (η Lyrae, abbreviated Eta Lyr, η Lyr) is the primary or 'A' component of a triple star system[7] in the constellation of Lyra. It is approximately 1,390 light-years from the Sun.[1]

Eta Lyrae
Observation data
Epoch J2000      Equinox J2000
Constellation Lyra
Right ascension  19h 13m 45.48832s[1]
Declination +39° 08′ 45.4801″[1]
Apparent magnitude (V) 4.40[2]
Characteristics
Spectral type B2.5IV[2]
Astrometry
Radial velocity (Rv)−8.1±0.9[1] km/s
Proper motion (μ) RA: −0.60[1] mas/yr
Dec.: −1.26[1] mas/yr
Parallax (π)2.35 ± 0.13[1] mas
Distance1,390 ± 80 ly
(430 ± 20 pc)
Absolute magnitude (MV)−3.71[3]
Orbit[4]
Period (P)56.4 d
Eccentricity (e)0.53
Semi-amplitude (K1)
(primary)		2.9 km/s
Details
Luminosity6,605[3] L☉
Surface gravity (log g)3.38[5] cgs
Temperature17,360[5] K
Metallicity [Fe/H]−0.01[5] dex
Rotational velocity (v sin i)10[6] km/s
Other designations
η Lyr, 20 Lyr, HD 180163, HIP 94481, HR 7298, SAO 68010, BD+38°3490, WDS 19138+3909[2]
Database references
SIMBADdata

The secondary or 'B' component is the star BD +38 3491.[7] Eta Lyrae is itself a spectroscopic binary[7] with components designated Aa (formally named Aladfar /əˈlædfɑːr/, the traditional name of the system)[8] and Ab.

Nomenclature

η Lyrae (Latinised to Eta Lyrae) is the binary star's Bayer designation. Its designation as the A component of a triple star system, and of its two constituents as the Aa and Ab components, derives from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[9]

'BD +38 3491' is the 'B' component's designation in the Bonner Durchmusterung astrometric star catalogue.

Eta Lyrae bore the traditional name Aladfar, from the Arabic الأظفر al-ʼuẓfur "the talons (of the swooping eagle)", a name it shares with Mu Lyrae (though the latter is typically spelled Alathfar).[10] The Working Group on Star Names (WGSN)[11] has approved the name Aladfar for the Aa component of the triple star system (the primary component of Eta Lyrae).[8]

Properties

Eta Lyrae belongs to spectral class B2.5IV and has apparent magnitude of +4.40.[2] It is a single-lined spectroscopic binary, with a very small radial velocity variation of 2.8 km/s. The orbital period is 56.4 d.[4]

References
  1. 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.
  2. "* eta Lyr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 25 July 2015.
  3. 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.
  4. Abt, H. A.; Levy, S. G. (1978). "Binaries among B2-B5 IV, V absorption and emission stars". The Astrophysical Journal Supplement Series. 36: 241. Bibcode:1978ApJS...36..241A. doi:10.1086/190498.
  5. Cenarro, A. J.; Peletier, R. F.; Sanchez-Blazquez, P.; Selam, S. O.; Toloba, E.; Cardiel, N.; Falcon-Barroso, J.; Gorgas, J.; Jimenez-Vicente, J.; Vazdekis, A. (2007). "Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters". Monthly Notices of the Royal Astronomical Society. 374 (2): 664. arXiv:astro-ph/0611618. Bibcode:2007MNRAS.374..664C. doi:10.1111/j.1365-2966.2006.11196.x.
  6. Prugniel, Ph.; Vauglin, I.; Koleva, M. (2011). "The atmospheric parameters and spectral interpolator for the MILES stars". Astronomy & Astrophysics. 531: A165. arXiv:1104.4952. Bibcode:2011A&A...531A.165P. doi:10.1051/0004-6361/201116769.
  7. "Washington Double Star Catalog". United States Naval Observatory. Archived from the original on 14 February 2011. Retrieved 2 January 2018.
  8. "Naming Stars". IAU.org. Retrieved 16 December 2017.
  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. Richard Hinckley Allen (25 October 2018). Star-Names and Their Meanings. Creative Media Partners, LLC. ISBN 978-0-344-21405-9.
  11. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
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