Astronomy:VW Cephei
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Cepheus[2] |
| Right ascension | 20h 37m 21.5439s[3] |
| Declination | +75° 36′ 01.467″[3] |
| Apparent magnitude (V) | 7.30 – 7.84[4] |
| Characteristics | |
| A | |
| Spectral type | G8V[5] |
| B | |
| Spectral type | K0V[5] |
| Astrometry | |
| Proper motion (μ) | RA: +308.71[3] mas/yr Dec.: +540.86[3] mas/yr |
| Parallax (π) | 36.25 ± 0.58[3] mas |
| Distance | 91.00 ± 0.95 ly (27.90±0.29 pc) |
| Details | |
| A | |
| Mass | 1.13[4] M☉ |
| Radius | 0.99[4] R☉ |
| Temperature | 5,050[4] K |
| Age | 9.029[6] Gyr |
| B | |
| Mass | 0.34[4] M☉ |
| Radius | 0.57[4] R☉ |
| Temperature | 5,342±15[4] K |
| Age | 9.029[6] Gyr |
| C | |
| Mass | 0.74±0.07[7] M☉ |
| Orbit[4] | |
| Primary | A |
| Companion | B |
| Period (P) | 0.278315349(12)[7] days |
| Semi-major axis (a) | (1.412±0.010)×106 km (2.030±0.014 R☉) |
| Inclination (i) | 62.86±0.04° |
| Orbit[7] | |
| Primary | AB |
| Companion | C |
| Period (P) | 29.79±0.08 years |
| Semi-major axis (a) | 4.33±0.20 astronomical unit|AU |
| Eccentricity (e) | 0.633±0.007 |
| Inclination (i) | 33.6±1.2° |
| Longitude of the node (Ω) | 17.7±3.1° |
| Argument of periastron (ω) (secondary) | 239.28±2.88° |
| Other designations | |
| Database references | |
| SIMBAD | data |
VW Cephei (VW Cep) is a triple star in the constellation Cepheus, located roughly at 90.6 light years from the Sun.
The two inner components form an eclipsing contact binary of W Ursae Majoris-type, whose two component stars share a common outer layer. Both are main-sequence stars smaller than the Sun. They take 0.2783 days (roughly 6.7 hours) to revolve around a common barycentre.[6] Jan Schilt discovered that the star is an eclipsing variable, in 1926.[8]
The third component has been detected by analysing the difference between the observed and the predicted time of eclipses, which is caused by the light-time effect of its orbital motion around the pair, and has been independently detected by astrometry.[7][4] It has an orbital period of 29.79 years around the inner pair.[4] A fourth component has also been proposed to explain additional changes in eclipse timing, but it was later found that the period variations are more likely caused by mass transfer between components via the Applegate mechanism, rather than the presence of a fourth companion.[4]
References
- ↑ Kreiner, J. M.; Winiarski, M. (January 1981). "Photoelectric observations and light curve variations of VW Cephei". Acta Astronomica 31 (3): 351–361. Bibcode: 1981AcA....31..351K. https://ui.adsabs.harvard.edu/abs/1981AcA....31..351K. Retrieved 7 December 2021.
- ↑ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A XHIP record for this object at VizieR.
- ↑ 3.0 3.1 3.2 3.3 van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode: 2007A&A...474..653V.
- ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 Mitnyan, T.; Bódi, A.; Szalai, T.; Vinkó, J.; Szatmáry, K.; Borkovits, T.; Bíró, B. I.; Hegedüs, T. et al. (2018-04-01). "The contact binary VW Cephei revisited: surface activity and period variation" (in en). Astronomy & Astrophysics 612: A91. doi:10.1051/0004-6361/201731402. ISSN 0004-6361. Bibcode: 2018A&A...612A..91M.
- ↑ 5.0 5.1 Yang, Yuan-Gui (February 2011). "A photometric study of the K-type contact binary EI CVn" (in en). Research in Astronomy and Astrophysics 11 (2): 181–190. doi:10.1088/1674-4527/11/2/006. ISSN 1674-4527. Bibcode: 2011RAA....11..181Y.
- ↑ 6.0 6.1 6.2 Latković, Olivera; Čeki, Atila; Lazarević, Sanja (May 2021). "Statistics of 700 Individually Studied W UMa Stars" (in en). The Astrophysical Journal Supplement Series 254 (1): 10. doi:10.3847/1538-4365/abeb23. ISSN 0067-0049. Bibcode: 2021ApJS..254...10L.
- ↑ 7.0 7.1 7.2 7.3 Zasche; Wolf, M. (2007). "Combining astrometry with the light-time effect: The case of VW Cep, zeta Phe and HT Vir". Astronomische Nachrichten 328 (9): 928–938. doi:10.1002/asna.200710828. Bibcode: 2007AN....328..928Z.
- ↑ Schilt, J. (November 1926). "Two new variables stars of the type of W Ursae Majoris". Astrophysical Journal 64: 215–224. doi:10.1086/143006. Bibcode: 1926ApJ....64..215S. https://articles.adsabs.harvard.edu/pdf/1926ApJ....64..215S. Retrieved 23 January 2025.
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