Delta1 Lyrae

Delta1 Lyrae, its name Latinized from δ1 Lyrae, is a binary star system in the northern constellation of Lyra. It is dimly visible to the naked eye at night with a combined apparent visual magnitude of 5.56.[2] The system is located at a distance of approximately 1,160 light years from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −26 km/s.[5] O. J. Eggen originally included this as a candidate member of the proposed Delta Lyrae cluster.[12]

For other stars with this Bayer designation, see δ Lyrae.
Delta1 Lyrae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Lyra
Right ascension 18h 53m 43.55924s[1]
Declination +36° 58′ 18.1891″[1]
Apparent magnitude (V) 5.56[2]
Characteristics
Spectral type B2.5V[3][4]
U−B color index −0.67[2]
B−V color index −0.15[2]
Astrometry
Radial velocity (Rv)−25.8[5] km/s
Proper motion (μ) RA: +1.350[1] mas/yr
Dec.: −2.985[1] mas/yr
Parallax (π)2.8072 ± 0.1334[1] mas
Distance1,160 ± 60 ly
(360 ± 20 pc)
Absolute magnitude (MV)−1.55[6]
Orbit[7]
Period (P)88.352 days
Semi-major axis (a)≥46.8 Gm (0.313 AU)
Eccentricity (e)0.37±0.03
Periastron epoch (T)2428406.613±0.500 JD
Argument of periastron (ω)
(secondary)		191.3±0.1°
Semi-amplitude (K1)
(primary)		39.7±1.8 km/s
Details
δ1 Lyr A
Mass7.9±0.1 M☉[4]
7.75±0.50 M☉[8]
6.6+0.68
−0.61[9] M☉
Luminosity838[6] L☉
Luminosity (bolometric)3,620[8] L☉
Surface gravity (log g)3.764±0.032 (3.848 polar)[10] cgs
Temperature20,350[8] K
Metallicity [Fe/H]−0.05[6] dex
Rotational velocity (v sin i)86±10[10] km/s
Age21.1±2.2 Myr[4]
9+9
−4[9] Myr
Other designations
Delta1 Lyr, 11 Lyrae, NSV 11504, BD+36°3307, GC 25934, HD 175426, HIP 92728, HR 7131, SAO 67537, WDS J18537+3658A, GSC 02650-02146[11]
Database references
SIMBADdata

The variable radial velocity of this star was discovered from photographic plates taken at the Yerkes Observatory in 1904.[13] The first set of orbital elements was computed by Frank Craig Jordan in 1916.[14] It is a single-lined spectroscopic binary with an orbital period of 88.4 days and an eccentricity (ovalness) of 0.37.[7]

The visible component of the pair has a blue-white hue with a stellar classification of B2.5V,[3][4] indicating that it is a B-type main-sequence star undergoing core hydrogen fusion. It is a few million years old with a relatively high rotation rate and around 7–8 times the mass of the Sun. The star is radiating about 3,620[8] times the Sun's luminosity from its photosphere at an effective temperature of 20,350 K.[8]

There is a magnitude 9.93 visual companion at an angular separation of 175.30 arcseconds along a position angle of 20°, as of 2012. This component was discovered by William Herschel.[15] It is an evolved giant star with a class of K2III at a distance of around 1,760 light years.[16]

References
  1. 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.
  2. Guetter, H. H. (October 1974), "UBV photometry of 180 early-type stars", Publications of the Astronomical Society of the Pacific, 86: 795–797, Bibcode:1974PASP...86..795G, doi:10.1086/129675.
  3. Guetter, Harry H. (April 1968), "Spectral classification of 239 early-type stars", Publications of the Astronomical Society of the Pacific, 80 (473): 197, Bibcode:1968PASP...80..197G, doi:10.1086/128611.
  4. Tetzlaff, 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.
  5. Wilson, Ralph Elmer (1953), General catalogue of stellar radial velocities, Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  6. 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.
  7. Richardson, E. H.; McKellar, A. (1957), "Redetermination of the spectrographic orbit of delta1 Lyrae", Publ. Dominion Astrophys. Obs., 10: 407–413, Bibcode:1958PDAO...10..407R. , p. 412
  8. Hohle, 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.
  9. Gullikson, Kevin; et al. (July 26, 2016), "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars", The Astronomical Journal, 152 (2): 40–53, arXiv:1604.06456, Bibcode:2016AJ....152...40G, doi:10.3847/0004-6256/152/2/40, S2CID 119179065.
  10. Huang, W.; Gies, D. R. (August 2008), "Stellar Rotation in Field and Cluster B Stars", The Astrophysical Journal, 683 (2): 1045–1051, arXiv:0805.2133, Bibcode:2008ApJ...683.1045H, doi:10.1086/590106.
  11. "del01 Lyr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-23.
  12. Eggen, O. J. (July 1983), "Concentrations in the Local Association- II. The northern concentrations including the alf Per, Pleiades, M 34 and del LYR clusters.", Monthly Notices of the Royal Astronomical Society, 204: 391–403, Bibcode:1983MNRAS.204..391E, doi:10.1093/mnras/204.2.391.
  13. Frost, E. B.; Adams, W. S. (1904), "Observations with the Bruce spectrograph", The Astrophysical Journal, 19: 352, Bibcode:1904ApJ....19..350F.
  14. Jordan, Frank Craig (1916), "The orbit of [delta]1 Lyrae", Publications of the Allegheny Observatory of the University of Pittsburgh, 3 (14): 119–124, Bibcode:1916PAllO...3..119J.
  15. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122: 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
  16. "BD+36 3308". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-23.
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