Delta2 Lyrae

For other stars with this Bayer designation, see δ Lyrae.
δ2 Lyrae
Location of δ2 Lyrae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Lyra
Right ascension 18h 54m 30.282689s[1]
Declination +36° 53′ 55.03167″[1]
Apparent magnitude (V) 4.22 – 4.33[2]
Characteristics
Spectral type M4 II[2]
U−B color index +1.65
B−V color index +1.68
Variable type SRc?[2]
Astrometry
Radial velocity (Rv)−25.55[citation needed] km/s
Proper motion (μ) RA: −6.598 mas/yr[1]
Dec.: 1.953 mas/yr[1]
Parallax (π)4.2352 ± 0.2951 mas[1]
Distance773+69
−39 ly
(237+21
−13 pc)[3]
Absolute magnitude (MV)−3.3[4]
Details
Mass4.5±1[5] M☉
Radius293+19
−22[6] R☉
Luminosity10,248±1,500[6] L☉
Surface gravity (log g)0[7] cgs
Temperature3,394±32[6] K
Age75[8][a] Myr
Other designations
Delta2 Lyrae, 12 Lyrae, HR 7139, BD+36°3319, HD 175588, SAO 67559, HIP 92791, GC 25959, CCDM J18545+3654, WDS J18545+3654
Database references
SIMBADdata

Delta2 Lyrae (δ2 Lyr) is a 4th magnitude star in the constellation Lyra, approximately 770 light years away from Earth. It is visible to the naked eye. It is one of the M4II spectral standard stars.[9]

Characteristics

It began life as a hot blue main sequence star, but now is a large cool asymptotic giant branch star with a degenerate carbon-oxygen core. It is a semi-regular variable star that has its brightness change by 0.2 magnitudes over an ill-defined period.[8] Delta2 Lyrae was a 5.0 M☉ star when still in the main sequence, but due to stellar mass loss it has lost 0.5 solar masses.[5] The star's photosphere has expanded to 290 times the size of the Sun, and is now radiating 10,200 times the luminosity of the Sun. It has cooled to 3,394 K (3,121 °C),[6] giving Delta2 Lyrae a reddish hue typical of M-type stars.[10]

Lyra with the δ Lyrae pair and surrounding cluster stars left of centre

It is the brightest member of the scattered open cluster Stephenson 1, also known as the δ Lyrae Cluster. Other known members include δ1 Lyrae, a handful of 8th-9th magnitudes stars, and at least thirty other stars down to 14th magnitude.[11][4]

Variability

A light curve for Delta2 Lyrae, plotted from Hipparcos data[12]

δ2 Lyrae is a variable star, probably a semiregular variable. It has a magnitude range of 4.22 to 4.33.[2]

Companion stars

Multiple star catalogues list several companions to δ2 Lyrae, with designations such as ADS 11825. Two of them are a close pair of 10th magnitude stars about 87" from δ2, designated components B and C.[13] The spectral type of the pair suggests that they are at the same distance as Delta2 Lyrae, which could mean that the three stars form a triple star system. In this case, the ADS 11825BC pair would be 24,000 AU away from δ2 Lyrae, and it would take 24,000 years for it to make an orbit. The two stars in the BC system take at least 10,500 years to make an orbit and are separated by 600 AU.[citation needed]

Delta2 Lyrae was once thought to form a visual binary with the star Delta1 Lyrae, but it does not, only appearing to do so if seen from Earth's direction.[8]

Notes

  1. ^ For a mass of 6 solar masses.

References

  1. ^ a b c d Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b c d 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.
  3. ^ Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021-03-01). "Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3". The Astronomical Journal. 161 (3): 147. arXiv:2012.05220. Bibcode:2021AJ....161..147B. doi:10.3847/1538-3881/abd806. ISSN 0004-6256. Data about this star can be seen here.
  4. ^ a b Eggen, O. J. (April 1968). "Photometric evidence for the existence of a delta Lyrae cluster". Astrophysical Journal. 152: 77. Bibcode:1968ApJ...152...77E. doi:10.1086/149525.
  5. ^ a b Halabi, Ghina M.; Eid, Mounib El (2015). "Exploring masses and CNO surface abundances of red giant stars". Monthly Notices of the Royal Astronomical Society. 451 (3): 2957. arXiv:1507.01517. Bibcode:2015MNRAS.451.2957H. doi:10.1093/mnras/stv1141. S2CID 118707332.
  6. ^ a b c d Baines, Ellyn K.; Thomas Armstrong, J.; Clark, James H.; Gorney, Jim; Hutter, Donald J.; Jorgensen, Anders M.; Kyte, Casey; Mozurkewich, David; Nisley, Ishara; Sanborn, Jason; Schmitt, Henrique R.; Van Belle, Gerard T. (2021). "Angular Diameters and Fundamental Parameters of Forty-four Stars from the Navy Precision Optical Interferometer". The Astronomical Journal. 162 (5): 198. arXiv:2211.09030. Bibcode:2021AJ....162..198B. doi:10.3847/1538-3881/ac2431.
  7. ^ Levesque, E. M.; Massey, P.; Olsen, K. A. G.; Plez, B.; Josselin, E.; Maeder, A.; Meynet, G. (2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not as Cool as We Thought". The Astrophysical Journal. 628 (2): 973–985. arXiv:astro-ph/0504337. Bibcode:2005ApJ...628..973L. doi:10.1086/430901. S2CID 15109583.
  8. ^ a b c Kaler, Jim. "DELTA-2 LYR (Delta-2 Lyrae)". stars.astro.illinois.edu.
  9. ^ Garcia, B. (1989). "A list of MK standard stars". Bulletin d'Information du Centre de Données Stellaires. 36: 27. Bibcode:1989BICDS..36...27G.
  10. ^ "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. Archived from the original on December 3, 2013. Retrieved 2012-01-16.
  11. ^ Stephenson, C. B. (1959). "A Possible New Galactic Cluster Involving δ Lyrae". Publications of the Astronomical Society of the Pacific. 71 (419): 145. Bibcode:1959PASP...71..145S. doi:10.1086/127349.
  12. ^ "/ftp/cats/more/HIP/cdroms/cats". Centre de Données astronomiques de Strasbourg. Strasbourg astronomical Data Center. Retrieved 15 October 2022.
  13. ^ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.