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Eta Lyrae

Coordinates:Sky map19h 13m 45s, 5+° 39′ 08″
From Wikipedia, the free encyclopedia
Star in the constellation Lyra
Eta Lyrae
Observation data
Epoch J2000      Equinox J2000
ConstellationLyra
Right ascension19h 13m 45.48832s[1]
Declination+39° 08′ 45.4801″[1]
Apparent magnitude (V)4.43[2]
Characteristics
Spectral typeB2.5IV[3]
B−Vcolor index−0.150±0.002[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 mas[1]
Distance1,390 ± 80 ly
(430 ± 20 pc)
Absolute magnitude (MV)−3.71[2]
Orbit[4]
Period (P)56.4±0.5 d
Semi-major axis (a)≥ 1.841 Gm (0.01231 AU)
Eccentricity (e)0.53±0.12
Periastronepoch (T)2,441,868.4±3.4 JD
Argument of periastron (ω)
(secondary)		337±28°
Semi-amplitude (K1)
(primary)		2.8±0.5 km/s
Details
Mass9.97±0.98 M☉[5]
10.1±1.0[6] M☉
Radius4.3[7] R☉
Luminosity6,605[2] L☉
Luminosity (bolometric)19,095[5] L☉
Surface gravity (log g)3.38[8] cgs
Temperature17,360 K[8]
19,525[5] K
Metallicity [Fe/H]−0.01[8] dex
Rotational velocity (v sin i)10[9] km/s
Age22.5±2.6[6] Myr
Other designations
Eta Lyr or η Lyr,20 Lyr,BD+38°3490,HD 180163,HIP 94481,HR 7298,SAO 68010,WDS 19138+3909[10]
Database references
SIMBADdata

Eta Lyrae, a nameLatinized fromη Lyrae, is a likelybinary star[11] system in the northernconstellation ofLyra. It has the traditional nameAladfar/əˈlædfɑːr/ and is faintly visible to the naked eye with anapparent visual magnitude of 4.43.[2] The system is located at a distance of approximately 1,390 light years from theSun based onparallax, but is drifting closer with aradial velocity of −8 km/s.[1]

Nomenclature

[edit]

η Lyrae (Latinised toEta Lyrae) is the binary star'sBayer designation. Its designation as theA component of a double star, and of its two constituents as theAa andAb components, derives from the convention used by the Washington Multiplicity Catalog (WMC) formultiple star systems, and adopted by theInternational Astronomical Union (IAU).[12]

'BD +38 3491' is the 'B' component's designation in theBonner Durchmusterung astrometricstar catalogue.

Eta Lyrae bore the traditional nameAladfar, from theArabicالأظفرal-ʼuẓfur "the talons (of the swooping eagle)", a name it shares withMu Lyrae (though the latter is typically spelledAlathfar).[13] TheWorking Group on Star Names (WGSN)[14] has approved the nameAladfar for the Aa component of the system (the primary component of Eta Lyrae).[15]

Properties

[edit]

The suspected radial velocity variations of this star in 1938 led to it being incorrectly classified as aBeta Cephei-type star, although there was some early disagreement about the variation.[16] In 1951,J. A. Pearce andR. M. Petrie also noted that the star appeared to have a variableradial velocity.[17] It was announced as a binary system byH. A. Abt andS. G. Levy in 1978, who listed it as a single-linedspectroscopic binary, albeit with marginalelements. The putative components have anorbital period of 56 days with aneccentricity (ovalness) of 0.5 and a smallradial velocity variation of2.8 km/s.[4]

The visible component of this system is a massiveB-type star with astellar classification of B2.5IV.[3] It is around 23[6] million years old with ten[6] times the mass of the Sun and a low rotational velocity. The star is radiating around 19,095 times the luminosity of the Sun from itsphotosphere at aneffective temperature of 19,525 K.[5] Amagnetic field has been detected with an average quadratic field strength of(169.0±115.9)×10−4 T.[18]

The magnitude 8.58 star BD +38 3491 forms avisual companion to this pair. It is designated Eta Lyrae B in theWashington Double Star Catalog, and is located at anangular separation of28.40 arcseconds along aposition angle of 81°, as of 2017.[19]

References

[edit]
  1. ^abcdefgvan 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. ^abcdeAnderson, 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.S2CID 119257644.
  3. ^abLesh, Janet Rountree (December 1968), "The Kinematics of the Gould Belt: an Expanding Group?",Astrophysical Journal Supplement,17: 371,Bibcode:1968ApJS...17..371L,doi:10.1086/190179
  4. ^abAbt, 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. ^abcdHohle, M. M.; et al. (April 2010). "Masses and luminosities of O- and B-type stars and red supergiants".Astronomische Nachrichten.331 (4): 349.arXiv:1003.2335.Bibcode:2010AN....331..349H.doi:10.1002/asna.200911355.S2CID 111387483.
  6. ^abcdTetzlaff, N.; et al. (January 2011)."A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun".Monthly Notices of the Royal Astronomical Society.410 (1):190–200.arXiv:1007.4883.Bibcode:2011MNRAS.410..190T.doi:10.1111/j.1365-2966.2010.17434.x.S2CID 118629873.
  7. ^Pasinetti Fracassini, L. E.; et al. (2001). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)".Astronomy & Astrophysics.367 (2) (Third ed.):521–24.arXiv:astro-ph/0012289.Bibcode:2001A&A...367..521P.doi:10.1051/0004-6361:20000451.S2CID 425754.
  8. ^abcCenarro, A. J.; et al. (2007)."Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters".Monthly Notices of the Royal Astronomical Society.374 (2):664–690.arXiv:astro-ph/0611618.Bibcode:2007MNRAS.374..664C.doi:10.1111/j.1365-2966.2006.11196.x.S2CID 119428437.
  9. ^Prugniel, Ph.; et al. (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.S2CID 54940439.
  10. ^"* eta Lyr".SIMBAD.Centre de données astronomiques de Strasbourg. Retrieved25 July 2015.
  11. ^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.
  12. ^Hessman, F. V.; et al. (2010). "On the naming convention used for multiple star systems and extrasolar planets".arXiv:1012.0707 [astro-ph.SR].
  13. ^Allen, Richard Hinckley (25 October 2018).Star-Names and Their Meanings. Creative Media Partners, LLC.ISBN 978-0-344-21405-9.
  14. ^"IAU Working Group on Star Names (WGSN)". Retrieved22 May 2016.
  15. ^"Naming Stars". IAU.org. Retrieved16 December 2017.
  16. ^Heard, J. F. (1949). "An Analysis of Radial-Velocity Measures of Eight Stars Formerly Assigned to the Beta Cephei Group".The Astrophysical Journal.109: 185.Bibcode:1949ApJ...109..185H.doi:10.1086/145122.
  17. ^Pearce, J. A.; Petrie, R. M. (1951). "Revised radial velocities of seventy-nine B-type stars".Publications of the Dominion Astrophysical Observatory Victoria.8:409–427.Bibcode:1951PDAO....8..409P.
  18. ^Bychkov, V. D.; et al. (August 2003). "Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type stars".Astronomy and Astrophysics.407 (2):631–642.arXiv:astro-ph/0307356.Bibcode:2003A&A...407..631B.doi:10.1051/0004-6361:20030741.S2CID 14184105.
  19. ^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.
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