Delta1 Lyrae

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 mas[1]
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

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]

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]

  1. ^ a b c d e f Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Guetter1974 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Guetter1968 was invoked but never defined (see the help page).
  4. ^ a b c d Cite error: The named reference Tetzlaff2011 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Wilson1953 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Richardson_McKellar_1957 was invoked but never defined (see the help page).
  8. ^ a b c d e Cite error: The named reference Hohle2010 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Gullikson_et_al_2016 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Huang_Gies_2008 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Eggen1983 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Frost_Adams_1904 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Jordan1916 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Mason_et_al_2014 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference SIMBAD_B was invoked but never defined (see the help page).