Pi Cephei
Pi Cephei (π Cephei) is a trinary star located in the constellation Cepheus.[6] With a combined apparent magnitude of about 4.4,[2] the system is faintly visible to the naked eye. The inner pair of stars orbits in 1.5 years while the outer companion completes one orbit in about 160 years.[6]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 23h 07m 53.854s[1] |
| Declination | +75° 23′ 15.00″[1] |
| Apparent magnitude (V) | 4.419[2] 4.61[3] + 6.75[4]) |
| Characteristics | |
| Spectral type | G7III[5] / F5V[5] / A7V-A9V[6] |
| U−B color index | -0.46 |
| B−V color index | 0.8 |
| Astrometry | |
| Radial velocity (Rv) | -18.6 ± 0.9 km/s |
| Proper motion (μ) | RA: 6.81 ± 1.05[1] mas/yr Dec.: -34.06 ± 0.88[1] mas/yr |
| Parallax (π) | 13.8 ± 0.41[6] mas |
| Distance | 236 ± 7 ly (72 ± 2 pc) |
| Absolute magnitude (MV) | 0.24 |
| Orbit[5] | |
| Primary | π Cep Aa |
| Companion | π Cep Ab |
| Period (P) | 556.72 ± 0.05 d |
| Semi-major axis (a) | 39.0 ± 3.9 mas[6] |
| Eccentricity (e) | 0.297 ± 0.006 |
| Inclination (i) | 99.0 ± 2.5[6]° |
| Longitude of the node (Ω) | 109.2 ± 3.5[6]° |
| Periastron epoch (T) | 2,439,172.9 ± 1.6 |
| Argument of periastron (ω) (secondary) | 7.6 ± 1.2° |
| Semi-amplitude (K1) (primary) | 24.18 ± 0.15 km/s |
| Orbit[7] | |
| Primary | π Cephei A (Aa + Ab) |
| Companion | π Cephei B |
| Period (P) | 162.8 ± 2.8 yr |
| Semi-major axis (a) | 0.810 ± 0.050″ |
| Eccentricity (e) | 0.5968 ± 0.0067 |
| Inclination (i) | 30.0 ± 3.0° |
| Longitude of the node (Ω) | 90.3 ± 4.9° |
| Periastron epoch (T) | B 1934.573 ± 0.35 |
| Argument of periastron (ω) (secondary) | 90.0 ± 4.4° |
| Details[6] | |
| π Cep Aa | |
| Mass | 3.63 ± 0.53 M☉ |
| Surface gravity (log g) | 3.05±0.11[8] cgs |
| Temperature | 5,226±92[8] K |
| Metallicity [Fe/H] | 0.29±0.05[8] dex |
| Age | 100[8] Myr |
| π Cep Ab | |
| Mass | 3.27 ± 0.48 M☉ |
| π Cep B | |
| Mass | 1.93 ± 0.23 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
Pi Cephei was found to have a visual companion star by Otto Wilhelm von Struve in 1843.[6] That the primary is itself a spectroscopic binary was first noticed by William Wallace Campbell in 1901 using photographic plates taken at Lick Observatory.[10]
References
- van Leeuwen, F. (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. Vizier catalog entry
- Hauck, B.; Mermilliod, M. (1998). "Uvbybeta photoelectric photometric catalogue". Astronomy and Astrophysics Supplement. 129 (3): 431–433. Bibcode:1998A&AS..129..431H. doi:10.1051/aas:1998195.Vizier catalog entry
- Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H.
- Fabricius, C.; Høg, E.; Makarov, V. V.; Mason, B. D.; Wycoff, G. L.; Urban, S. E. (2002). "The Tycho double star catalogue". Astronomy and Astrophysics. 384: 180–189. Bibcode:2002A&A...384..180F. doi:10.1051/0004-6361:20011822.
- Scarfe, C. D.; et al. (1983). "Revised orbits for 105 Herculis and Pi Cephei A and a model for the Pi Cephei system". Monthly Notices of the Royal Astronomical Society. 203: 103–116. Bibcode:1983MNRAS.203..103S. doi:10.1093/mnras/203.1.103.
- Gatewood, George; et al. (2001). "Hipparcos and MAP Studies of the Triple Star π Cephei". The Astrophysical Journal. 549 (2): 1145–1150. Bibcode:2001ApJ...549.1145G. doi:10.1086/319458.
- "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Retrieved 3 June 2017.
- Feuillet, Diane K.; Bovy, Jo; Holtzman, Jon; Girardi, Léo; MacDonald, Nick; Majewski, Steven R.; Nidever, David L. (2016). "Determining Ages of APOGEE Giants with Known Distances". The Astrophysical Journal. 817 (1): 40. arXiv:1511.04088. Bibcode:2016ApJ...817...40F. doi:10.3847/0004-637X/817/1/40. S2CID 118675933.
- "* pi. Cep". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2013-09-01.
- Campbell, William Wallace (1901). "Some recent results secured with the Mills spectrograph". Lick Observatory Bulletin. 1 (4): 22–25. Bibcode:1901LicOB...1...22C. doi:10.5479/ADS/bib/1901LicOB.1.22C.
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