LY Aurigae

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LY Aurigae
M 38.jpg
LY Aurigae is the bright star in the southeast corner of this picture of Messier 38
Observation data
Epoch J2000      Equinox J2000
Constellation Auriga
Right ascension  05h 29m 42.650s[1]
Declination +35° 22′ 30.09″[1]
Apparent magnitude (V) 6.85[2] (6.66 - 7.35[3])
Spectral type O9II + O9III + B0.5III[4]
U−B color index −0.78[5]
B−V color index +0.20[5]
Variable type β Lyr[2]
Radial velocity (Rv)5.40[6] km/s
Proper motion (μ) RA: −0.20 ± 3.19[1] mas/yr
Dec.: −1.17 ± 2.07[1] mas/yr
Parallax (π)3.28 ± 2.40[1] mas
Distanceapprox. 1,000 ly
(approx. 300 pc)
Absolute magnitude (MV)−5.62 + −5.11 + −4.43[4]
Period (P)4.0025 days
Semi-major axis (a)36.1 AU
Eccentricity (e)0.0
Inclination (i)87.7°
Semi-amplitude (K1)
161.9 km/s
Semi-amplitude (K2)
294.3 km/s
Period (P)20.4642 days
Eccentricity (e)0.246
Semi-amplitude (K1)
33.0 km/s
Mass25.5 M
Radius16.1 R
Luminosity214,000 L
Surface gravity (log g)3.425 cgs
Temperature31,000 K
Rotational velocity (v sin i)194 km/s
Mass14.0 M
Radius12.6 R
Luminosity135,000 L
Surface gravity (log g)3.378 cgs
Temperature31,150 K
Rotational velocity (v sin i)152 km/s
Luminosity47,000 L
Surface gravity (log g)4.00 cgs
Temperature26,000 K
Rotational velocity (v sin i)30 km/s
Other designations
LY Aurigae, BD+35°1137, HD 35921, SAO 58105, HIP 25733, WDS J05297+3523, AAVSO 0523+35
Database references

LY Aurigae is a multiple star system in the constellation Auriga. It is an eclipsing binary variable star, dropping in brightness by 0.7 magnitudes every 4 days. The system is around a thousand light years away in the Auriga OB1 stellar association.


LY Aurigae is a close visual binary; the two stars are magnitude 6.85[7] and magnitude 8.35[8] 0.6 arc-seconds apart. Each star is also a spectroscopic binary.

LY Aur A is a double-lined spectroscopic binary with an O9 bright giant and an O9 giant star in contact and eclipsing each other as they orbit every 4 days, it is classified as a Beta Lyr eclipsing variable system. The primary eclipse is 0.69 magnitudes deep and the secondary eclipse is 0.60 magnitudes.[9] Because of the contact nature of the system and the deformed shapes of the stars, the magnitude varies constantly throughout the orbital cycle; the orbital period is slowly changing due to mass exchange between the stars. Each star is over a hundred thousand times the luminosity of the sun.[4]

LY Aur B is a single-lined spectroscopic binary with an orbital period of 20.5 days. It is probably an early B main sequence star and the companion is undetectable; the two stars combined are 47,000 times the luminosity of the sun.[4]


  1. ^ a b c d e van Leeuwen, F. (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. Vizier catalog entry
  2. ^ a b Stickland, D. J.; et al. (1994). "Spectroscopic binary orbits from ultraviolet radial velocities. Paper 15: LY Aurigae (HD 35921)". The Observatory. 114: 107–113. Bibcode:1994Obs...114..107S.
  3. ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  4. ^ a b c d e f g Mayer, Pavel; Drechsel, Horst; Harmanec, Petr; Yang, Stephenson; Šlechta, Miroslav (2013). "The O-type eclipsing contact binary LY Aurigae - member of a quadruple system". Astronomy & Astrophysics. 559: A22. Bibcode:2013A&A...559A..22M. doi:10.1051/0004-6361/201322153.
  5. ^ a b Mayer, P.; Papoušek, J. (1988). "New photometric data on LY Aurigae". Contributions of the Astronomical Institute of Brno. 26. Bibcode:1988CoBrn..26.....M.
  6. ^ Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; Levato, H.; Morrell, N. I.; Torres, G.; Udry, S. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213.
  7. ^ Paunzen, E. (2015). "A new catalogue of Strömgren-Crawford uvbyβ photometry". Astronomy & Astrophysics. 580: A23. arXiv:1506.04568. Bibcode:2015A&A...580A..23P. doi:10.1051/0004-6361/201526413.
  8. ^ Fabricius, C.; Høg, E.; Makarov, V. V.; Mason, B. D.; Wycoff, G. L.; Urban, S. E. (2002). "The Tycho double star catalogue". Astronomy and Astrophysics. 384: 180. Bibcode:2002A&A...384..180F. doi:10.1051/0004-6361:20011822.
  9. ^ Malkov, O. Yu.; Oblak, E.; Snegireva, E. A.; Torra, J. (2006). "A catalogue of eclipsing variables". Astronomy and Astrophysics. 446 (2): 785. Bibcode:2006A&A...446..785M. doi:10.1051/0004-6361:20053137.

See also[edit]