VW Cephei
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| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| 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 mas/yr[3] Dec.: +540.86 mas/yr[3] |
| Parallax (π) | 36.25±0.58 mas[3] |
| Distance | 91.00 ± 0.95 ly (27.90±0.29 pc)[6] |
| Details[4] | |
| A | |
| Mass | 1.13 M☉ |
| Radius | 0.99 R☉ |
| Temperature | 5,050 K |
| Age | 9.029[7] Gyr |
| B | |
| Mass | 0.34 M☉ |
| Radius | 0.57 R☉ |
| Temperature | 5,342±15 K |
| Age | 9.029[7] Gyr |
| Orbit[4] | |
| Primary | A |
| Companion | B |
| Period (P) | 0.2783146[7] days |
| Semi-major axis (a) | (1.412±0.010)×106 km (2.030±0.014 R☉) |
| Inclination (i) | 62.86±0.04° |
| Other designations | |
| VW Cep, LHS 3565, SAO 9828, LTT 16039, BD+75 752, GJ 1255, GJ 9703, HD 197433, HIP 101750 | |
| Database references | |
| SIMBAD | data |
VW Cephei (VW Cep) is an eclipsing contact binary of W Ursae Majoris-type located roughly at 90.6 light years from the Sun, whose two component stars share a common outer layer. Because the two components share their outer layers, as the components of W Ursae Majoris do, they have the same stellar classification, and are classified as yellow G-type main sequence dwarfs. The components take 0.2783 days (roughly 6.7 hours) to revolve around a common barycentre.[7]
Jan Schilt discovered that the star is an eclipsing variable, in 1926.[8]
Possible companion(s)
[edit]The orbital period of VW Cephei show variations, which was long thought to be likely caused by the presence of one more perturbing unseen object around the eclipsing binary.[6] Several publications have tried to set constrains to putative orbital period and minimum mass for unseen component. The most recent article proposes an orbital period of 29.8 years for a stellar object with roughly three fourths the Sun's mass and a high orbital eccentricity (e=0.66).[6] Nevertheless, hints of an additional body in the system still subsist and the authors infer a period of 77.46 years and eccentricity of 0.54 for unseen fourth component. The minimum mass is unclear, tentatively assumed being as small as 0.19 solar masses according to Pribulla et al. (2007).[9] In any case orbital solutions are still blurry and further calculations are needed to provide a more robust model.
A more recent analysis suggest that the period variations are more likely caused by mass transfer between components via the Applegate mechanism, rather than the presence of unseen companions.[4]
References
[edit]- ^ 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. Retrieved 7 December 2021.
- ^ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
- ^ a b c d van Leeuwen, F. (November 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. S2CID 18759600.
- ^ a b c d Mitnyan, T.; Bódi, A.; Szalai, T.; Vinkó, J.; Szatmáry, K.; Borkovits, T.; Bíró, B. I.; Hegedüs, T.; Vida, K.; Pál, A. (2018-04-01). "The contact binary VW Cephei revisited: surface activity and period variation". Astronomy & Astrophysics. 612: A91. arXiv:1801.06036. Bibcode:2018A&A...612A..91M. doi:10.1051/0004-6361/201731402. ISSN 0004-6361.
- ^ a b Yang, Yuan-Gui (February 2011). "A photometric study of the K-type contact binary EI CVn". Research in Astronomy and Astrophysics. 11 (2): 181–190. Bibcode:2011RAA....11..181Y. doi:10.1088/1674-4527/11/2/006. ISSN 1674-4527.
- ^ a b c 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. arXiv:0711.3980. Bibcode:2007AN....328..928Z. doi:10.1002/asna.200710828. S2CID 14956926.
- ^ a b c d Latković, Olivera; Čeki, Atila; Lazarević, Sanja (May 2021). "Statistics of 700 Individually Studied W UMa Stars". The Astrophysical Journal Supplement Series. 254 (1): 10. arXiv:2103.06693. Bibcode:2021ApJS..254...10L. doi:10.3847/1538-4365/abeb23. ISSN 0067-0049.
- ^ Schilt, J. (November 1926). "Two new variables stars of the type of W Ursae Majoris". Astrophysical Journal. 64: 215–224. Bibcode:1926ApJ....64..215S. doi:10.1086/143006. Retrieved 23 January 2025.
- ^ Pribulla; Chochol, D.; Tremko, J.; Parimucha, S.; Vanko, M.; Kreiner, J. M. (2007). "Period study of the contact system VW Cep". Contributions of the Astronomical Observatory Skalnate Pleso. 30 (2): 117–139. arXiv:0711.3980. Bibcode:2000CoSka..30..117P. doi:10.1002/asna.200710828. S2CID 14956926.
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