μ Lyrae, Latinized as Mu Lyrae, is a solitary[8] star in the northern constellation Lyra. It has the traditional name Alathfar /əˈlæθfɑːr/, from the Arabic الأظفار al-ʼaẓfār "the talons (of the swooping eagle)", a name it shares with Eta Lyrae[9] (though the latter is spelled "Aladfar" by the IAU).[10] This white-hued object is visible to the naked eye as faint point of light with an apparent visual magnitude of 5.11.[2] It is located approximately 412 light years distant from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −24 km/s.[2]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 18h 24m 13.78599s[1] |
| Declination | +39° 30′ 26.0473″[1] |
| Apparent magnitude (V) | 5.11[2] |
| Characteristics | |
| Evolutionary stage | subgiant[3] |
| Spectral type | A3IVn[4] |
| U−B color index | +0.07[5] |
| B−V color index | +0.047±0.004[2] |
| Astrometry | |
| Radial velocity (Rv) | −24.0±4.2[2] km/s |
| Proper motion (μ) | RA: −21.825±0.260[1] mas/yr Dec.: −4.460±0.288[1] mas/yr |
| Parallax (π) | 7.9161 ± 0.1438 mas[1] |
| Distance | 412 ± 7 ly (126 ± 2 pc) |
| Absolute magnitude (MV) | –0.53[2] |
| Details | |
| Mass | 3.04±0.04[3] M☉ |
| Radius | 4.5[6] R☉ |
| Luminosity | 200+23 −10[3] L☉ |
| Temperature | 9,016+167 −165[3] K |
| Rotational velocity (v sin i) | 165[3] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
This object has evolved off the main sequence,[3] becoming a subgiant with a stellar classification of A0 IV.[4] It has a fairly high rate of spin, showing a projected rotational velocity of 165 km/s.[3] This is giving the star an equatorial bulge that is an estimated 17% larger than the polar radius.[11] The star has three[3] times the mass of the Sun and about 4.5[6] times the Sun's radius. It is radiating 200[3] times the Sun's luminosity from its photosphere at an effective temperature of 9,016 K.[3]
References
edit- ^ a b c d e f Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b c d e f 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, S2CID 119257644.
- ^ a b c d e f g h i j Zorec, J.; Royer, F. (January 2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
- ^ a b Van Belle, Gerard T.; von Braun, Kaspar (2009). "Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars". The Astrophysical Journal. 694 (2): 1085–1098. arXiv:0901.1206. Bibcode:2009ApJ...694.1085V. doi:10.1088/0004-637X/694/2/1085. S2CID 18370219.
- ^ Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
- ^ a b Pasinetti Fracassini, L. E.; et al. (February 2001). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)". Astronomy and Astrophysics. 367 (2) (Third ed.): 521–524. arXiv:astro-ph/0012289. Bibcode:2001A&A...367..521P. doi:10.1051/0004-6361:20000451. S2CID 425754.
- ^ "mu Lyr". SIMBAD. Centre de données astronomiques de Strasbourg.
- ^ 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.
- ^ Allen, Richard Hinckley (2018). Star-Names and Their Meanings. Creative Media Partners, LLC. ISBN 978-0-344-21405-9.
- ^ "Naming Stars". IAU.org. Retrieved 16 December 2017.
- ^ van Belle, Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2, S2CID 119273474
External links
edit- Kaler, James B. (October 7, 2011). "Al Athfar". STARS. Retrieved 2019-09-25.