Astronomy:Delta2 Lyrae
  | |
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Lyra |
| Right ascension | 18h 54m 30.28269s[1] |
| Declination | +36° 53′ 55.0317″[1] |
| Apparent magnitude (V) | 4.22 – 4.33[2] |
| Characteristics | |
| Evolutionary stage | AGB[3] |
| 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 km/s |
| Proper motion (μ) | RA: −6.598[1] mas/yr Dec.: 1.953[1] mas/yr |
| Parallax (π) | 4.2352 ± 0.2951[1] mas |
| Distance | 770+68 −42 ly (237+21 −13 pc) |
| Absolute magnitude (MV) | −3.3[4] |
| Details | |
| Mass | 4.5±1[5] M☉ |
| Radius | 293+19 −22[6] R☉ |
| Luminosity | 10,248±1,500[6] L☉ |
| Surface gravity (log g) | 0[7] cgs |
| Temperature | 3,394±32[6] K |
| Age | 75[8][lower-alpha 1] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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]
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
δ2 Lyrae is a variable star, probably a semiregular variable. It has a magnitude range of 4.22 to 4.33.[2]
Companion stars
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
- ↑ For a mass of 6 solar masses.
References
- ↑ 1.0 1.1 1.2 1.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 2.0 2.1 2.2 2.3 Samus, N. N. 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.
- ↑ Ragland, S.; Traub, W. A.; Berger, J. -P.; Danchi, W. C.; Monnier, J. D.; Willson, L. A.; Carleton, N. P.; Lacasse, M. G. et al. (2006). "First Surface-resolved Results with the Infrared Optical Telescope Array Imaging Interferometer: Detection of Asymmetries in Asymptotic Giant Branch Stars". The Astrophysical Journal 652 (1): 650. doi:10.1086/507453. Bibcode: 2006ApJ...652..650R.
- ↑ 4.0 4.1 Eggen, O. J. (April 1968). "Photometric evidence for the existence of a delta Lyrae cluster". Astrophysical Journal 152: 77. doi:10.1086/149525. Bibcode: 1968ApJ...152...77E.
- ↑ 5.0 5.1 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. doi:10.1093/mnras/stv1141. Bibcode: 2015MNRAS.451.2957H.
- ↑ 6.0 6.1 6.2 6.3 Baines, Ellyn K.; Thomas Armstrong, J.; Clark, James H.; Gorney, Jim; Hutter, Donald J.; Jorgensen, Anders M.; Kyte, Casey; Mozurkewich, David et al. (2021). "Angular Diameters and Fundamental Parameters of Forty-four Stars from the Navy Precision Optical Interferometer". The Astronomical Journal 162 (5): 198. doi:10.3847/1538-3881/ac2431. Bibcode: 2021AJ....162..198B.
- ↑ 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. doi:10.1086/430901. Bibcode: 2005ApJ...628..973L.
- ↑ 8.0 8.1 8.2 Kaler, Jim. "DELTA-2 LYR (Delta-2 Lyrae).". http://stars.astro.illinois.edu/sow/delta2lyr.html.
- ↑ Garcia, B. (1989). "A list of MK standard stars". Bulletin d'Information du Centre de Données Stellaires 36: 27. Bibcode: 1989BICDS..36...27G.
- ↑ "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html.
- ↑ Stephenson, C. B. (1959). "A Possible New Galactic Cluster Involving δ Lyrae". Publications of the Astronomical Society of the Pacific 71 (419): 145. doi:10.1086/127349. Bibcode: 1959PASP...71..145S.
- ↑ "/ftp/cats/more/HIP/cdroms/cats". Strasbourg astronomical Data Center. https://cdsarc.cds.unistra.fr/viz-bin/ftp-index?/ftp/cats/more/HIP/cdroms/cats.
Cite error: <ref> tag with name "b-j" defined in <references> is not used in prior text.
<ref> tag with name "wds" defined in <references> is not used in prior text.
 |  |
