U Cephei
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 01h 02m 18.4440s[1] |
| Declination | +81° 52′ 32.082″[1] |
| Apparent magnitude (V) | 6.92[2] |
| Characteristics | |
| Spectral type | B7/8V + G5/8III-IV[3] |
| Variable type | Eclipsing binary |
| Astrometry | |
| Radial velocity (Rv) | 5.0[4] km/s |
| Proper motion (μ) | RA: 23.811[1] mas/yr Dec.: −4.381[1] mas/yr |
| Parallax (π) | 5.1939±0.0238 mas[1] |
| Distance | 628 ± 3 ly (192.5 ± 0.9 pc) |
| Orbit[3] | |
| Primary | U Cep A (B-type star) |
| Companion | U Cep B (G-type star) |
| Period (P) | 2.4928 d |
| Semi-major axis (a) | 14.7 R☉ |
| Eccentricity (e) | 0 |
| Inclination (i) | 83° |
| Semi-amplitude (K1) (primary) | 120 km/s |
| Semi-amplitude (K2) (secondary) | 180 km/s |
| Details[3] | |
| U Cep A (B-type star) | |
| Mass | 4.2 M☉ |
| Radius | 2.9 R☉ |
| Temperature | 13600 K |
| U Cep B (G-type star) | |
| Mass | 2.8 M☉ |
| Radius | 4.7 R☉ |
| Temperature | 4950 K |
| Other designations | |
| Database references | |
| SIMBAD | data |
U Cephei is an eclipsing binary star discovered in 1880.[5][6] It consists of a blue-white main sequence star of spectral type B7/8V that is eclipsed every two and a half days by a less bright giant of type G5/8III-IV.[3] The drop in brightness lasts 4 hours and the system sees its apparent magnitude increase from 6.7 to 9.2. The total eclipse then lasts 2 hours before an increase in brightness for 4 hours. The two stars, separated by less than 10,000,000 kilometres (6,200,000 mi), exchange matter. This transfer towards the blue giant caused the system's orbital period to lengthen by 4 minutes during the 20th century. U Cephei is one of the brightest eclipsing binaries. Located near the north celestial pole, it can be monitored continuously with a 60 millimeter telescope.[7]
The system has two visual companions listed in the double and multiple star catalogs. U Cephei B is a twelfth magnitude star that, as of 2016, was located at an angular distance of 13.9 arcseconds and at a position angle of 63° from U Cephei A. It exhibits a common proper motion with the system, which indicates that it is physically linked to it. U Cephei C is another twelfth magnitude star, but it is only a purely optical double and its proximity to the system is a coincidence.[9]
See also
[edit]References
[edit]- ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
- ^ a b "V* U Cep". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2025-02-22.
- ^ a b c d Tupa, Peter R.; Deleo, Gary G.; McCluskey, George E.; Kondo, Yoji; Sahade, Jorge; Giménez, Alvaro; Caton, Daniel B. (2013). "Ultraviolet Spectroscopic Analysis of Transient Mass Flow Outburst in U Cephei". The Astrophysical Journal. 775 (1): 46. Bibcode:2013ApJ...775...46T. doi:10.1088/0004-637X/775/1/46.
- ^ Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication. Bibcode:1953GCRV..C......0W.
- ^ "U Cephei | astronomy | Britannica". www.britannica.com. Retrieved 2024-09-27.
- ^ Gimenez, A.; Guinan, E. F.; Gonzalez-Riestra, R. (1993-01-01). "UV and X-ray emission in the interacting binary U Cephei". Astronomy and Astrophysics Supplement Series. 97 (1): 261. Bibcode:1993A&AS...97..261G. ISSN 0365-0138.
- ^ "U Cephei Star Facts - Universe Guide". www.universeguide.com. January 25, 2015. Retrieved 2024-09-27.
- ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 1 October 2024.
- ^ Knott, George (June 9, 1882). "On the Variable Star U Cephei". Monthly Notices of the Royal Astronomical Society. 42 (8): 384–385. doi:10.1093/mnras/42.8.384a. Retrieved September 27, 2024.
