Eta Lyrae

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Template:Short description Template:Sky

Eta Lyrae
Observation data
Epoch J2000      Equinox J2000
Constellation Lyra
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 4.43[2]
Characteristics
Spectral type B2.5IV[3]
B−V Template:Engvar Template:Val[2]
Astrometry
Radial velocity (Rv)Template:Val[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]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)−3.71[2]
Orbit[4]
Period (P)Template:Val
Semi-major axis (a)≥ Template:Convert
Eccentricity (e)Template:Val
Periastron epoch (T)Template:Val
Argument of periastron (ω)
(secondary)		Template:Val°
Semi-amplitude (K1)
(primary)		Template:Val km/s
Details
MassTemplate:Val[5]
Template:Val[6] Template:Solar mass
Radius4.3[7] Template:Solar radius
Luminosity6,605[2] Template:Solar luminosity
Luminosity (bolometric)19,095[5] Template:Solar luminosity
Surface gravity (log g)3.38[8] cgs
TemperatureTemplate:Val[8]
19,525[5] K
Metallicity [Fe/H]−0.01[8] dex
Rotational velocity (v sin i)10[9] km/s
AgeTemplate:Val[6] Myr
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Template:Odlist[10]
Database references
SIMBADdata

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Eta Lyrae, a name Latinized from η Lyrae, is a likely binary star[11] system in the northern constellation of Lyra. It has the traditional name Aladfar Template:IPAc-en and is faintly visible to the naked eye with an apparent visual magnitude of 4.43.[2] The system is located at a distance of approximately 1,390 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −8 km/s.[1]

Nomenclature

η Lyrae (Latinised to Eta Lyrae) is the binary star's Bayer designation. Its designation as the A component of a double star, 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).[12]

'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).[13] The Working Group on Star Names (WGSN)[14] has approved the name Aladfar for the Aa component of the system (the primary component of Eta Lyrae).[15]

Properties

The suspected radial velocity variations of this star in 1938 led to it being incorrectly classified as a Beta Cephei-type star, although there was some early disagreement about the variation.[16] In 1951, J. A. Pearce and R. M. Petrie also noted that the star appeared to have a variable radial velocity.[17] It was announced as a binary system by H. A. Abt and S. G. Levy in 1978, who listed it as a single-lined spectroscopic binary, albeit with marginal elements. The putative components have an orbital period of 56 days with an eccentricity (ovalness) of 0.5 and a small radial velocity variation of Template:Val.[4]

The visible component of this system is a massive B-type star with a stellar 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 its photosphere at an effective temperature of 19,525 K.[5] A magnetic field has been detected with an average quadratic field strength of Template:Val.[18]

The magnitude 8.58 star BD +38 3491 forms a visual companion to this pair. It is designated Eta Lyrae B in the Washington Double Star Catalog, and is located at an angular separation of Template:Val along a position angle of 81°, as of 2017.[19]

References

Template:Reflist

Template:Stars of Lyra

  1. ↑ a b c d e f g Cite error: Invalid <ref> tag; no text was provided for refs named vanLeeuwen2007
  2. ↑ a b c d e Cite error: Invalid <ref> tag; no text was provided for refs named Anderson_Francis_2012
  3. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named Lesh1968
  4. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named Abt_Levy_1978
  5. ↑ a b c d Cite error: Invalid <ref> tag; no text was provided for refs named Hohle_et_al_2010
  6. ↑ a b c d Cite error: Invalid <ref> tag; no text was provided for refs named Tetzlaff_et_al_2011
  7. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Pasinetti_Fracassini_et_al_2001
  8. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named Cenarro_et_al_2007
  9. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Prugniel_et_al_2011
  10. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named SIMBAD
  11. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Eggleton_Tokovinin_2008
  12. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named planetnaming
  13. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named allen
  14. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named WGSN
  15. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named IAU-LSN
  16. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Heard1949
  17. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Pearce_Petrie_1951
  18. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Bychkov_et_al_2003
  19. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Mason_et_al_2014
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