Astronomy:Theta Cephei
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| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Cepheus[1] |
| Right ascension | 20h 29m 34.86518s[2] |
| Declination | +62° 59′ 38.6216″[2] |
| Apparent magnitude (V) | 4.22[3] |
| Characteristics | |
| Spectral type | A7 III[4] or kA7hF1mF2[5][6] |
| U−B color index | +0.16[3] |
| B−V color index | +0.20[3] |
| Astrometry | |
| Radial velocity (Rv) | −6.8[7] km/s |
| Proper motion (μ) | RA: 34.798[2] mas/yr Dec.: −13.904[2] mas/yr |
| Parallax (π) | 23.481 ± 0.6894[2] mas |
| Distance | 139 ± 4 ly (43 ± 1 pc) |
| Absolute magnitude (MV) | +1.12[1] |
| Orbit[8] | |
| Period (P) | 914.3±7.0 d |
| Eccentricity (e) | 0.377±0.006 |
| Periastron epoch (T) | 2456991.3±8.5 JD |
| Argument of periapsis (ω) (primary) | 48.8±1.1° |
| Semi-amplitude (K1) (primary) | 7.72±0.06 km/s |
| Details | |
| primary | |
| Mass | 2.75[9] M☉ |
| Radius | 3.09+0.36 −0.25[10] R☉ |
| Luminosity | 46.5[9] L☉ |
| Surface gravity (log g) | 3.74[4] cgs |
| Temperature | 7,375+307 −404[10] K |
| Metallicity [Fe/H] | +0.27±0.04[1] dex |
| Rotational velocity (v sin i) | 52.0[4] km/s |
| Age | 55[9] Myr |
| companion | |
| Mass | >0.62[8] M☉ |
| Radius | 0.654+0.044 −0.102[8] R☉ |
| Temperature | 4,070+340 −130[8] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Theta Cephei is a white-hued binary star system in the northern constellation of Cepheus. Its name is a Bayer designation that is Latinized from θ Cephei, and abbreviated Theta Cep or θ Cep. The system is visible to the naked eye as a point of light with an apparent visual magnitude of 4.22.[3] Based on parallax measurements, it is located at a distance of approximately 139 light-years (43 pc) from the Earth.
This is a spectroscopic binary star system with an orbital period of 2.5 years;[8] the eccentricity was long thought to be low, at 0.03,[12] but calculations published in 2020 have put it at a much higher 0.377.[8] They are separated by 4.16 astronomical unit|AU.[13]
The primary component has a Stellar classification of A7III,[4] displaying as a metallic-line Am star.[5] At an estimated age of 55 million years,[9] it is spinning with a projected rotational velocity of 52 km/s.[4] The star has 2.75[9] times the mass of the Sun and three times the Sun's radius.[10] It is radiating 46.5[9] times the luminosity of the Sun from its photosphere at an effective temperature of 7,375 K.[10] The companion star is calculated to be about 400 times fainter than the primary. It is completely invisible in the spectrum, but is estimated to be a K7 main sequence star.[9]
Shared with η Cep, this star system has the title Al Kidr.[14] In Chinese, 天鈎 (Tiān Gōu), meaning Celestial Hook, refers to an asterism consisting of 4 Cephei, HD 194298, η Cephei, α Cephei, ξ Cephei, 26 Cephei, ι Cephei and ο Cephei.[15] Consequently, the Chinese name for θ Cephei itself is 天鈎三 (Tiān Gōu sān, English: the Third Star of Celestial Hook.).[16]
References
- ↑ 1.0 1.1 1.2 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.
- ↑ 2.0 2.1 2.2 2.3 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.
- ↑ 3.0 3.1 3.2 3.3 Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99): 99, Bibcode: 1966CoLPL...4...99J.
- ↑ 4.0 4.1 4.2 4.3 4.4 Takeda, Yoichi et al. (April 2012), "Lithium, Sodium, and Potassium Abundances in Sharp-Lined A-Type Stars", Publications of the Astronomical Society of Japan 64 (2): 15, doi:10.1093/pasj/64.2.38, 38, Bibcode: 2012PASJ...64...38T
- ↑ 5.0 5.1 Abt, Helmut A.; Morrell, Nidia I. (1995), "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars", The Astrophysical Journal Supplement Series 99: 135, doi:10.1086/192182, Bibcode: 1995ApJS...99..135A.
- ↑ Skiff, B. A (2014), "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009-2016)", VizieR On-line Data Catalog: B/Mk. Originally Published in: Lowell Observatory (October 2014) 1, Bibcode: 2014yCat....1.2023S.
- ↑ Evans, D. S. (1967), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and Their Applications 30: 57, Bibcode: 1967IAUS...30...57E.
- ↑ 8.0 8.1 8.2 8.3 8.4 8.5 Bischoff, Richard et al. (2020), "Spectroscopic orbit determination of the long periodic binary system θ Cep", Astronomische Nachrichten 341 (10): 989, doi:10.1002/asna.202013850, Bibcode: 2020AN....341..989B.
- ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 Fouesneau, M. et al. (2022), "Astrophysical parameters from Gaia DR2, 2MASS, and AllWISE", Astronomy and Astrophysics 662: A125, doi:10.1051/0004-6361/202141828, Bibcode: 2022A&A...662A.125F.
- ↑ 10.0 10.1 10.2 10.3 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. [http://vizier.u-strasbg.fr/viz-bin/VizieR-S?Gaia%20DR2%20 2243479676058593152 Gaia DR2 record for this source] at VizieR.
- ↑ "tet Cep". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tet+Cep.
- ↑ Abt, Helmut A. (March 1961), "The Frequency of Binaries among Metallic-Line Stars", Astrophysical Journal Supplement 6: 37, doi:10.1086/190060, Bibcode: 1961ApJS....6...37A.
- ↑ Trilling, D. E. et al. (April 2007), "Debris disks in main-sequence binary systems", The Astrophysical Journal 658 (2): 1264–1288, doi:10.1086/511668, Bibcode: 2007ApJ...658.1289T.
- ↑ Allen, Richard Hinckley (2013), Star Names: Their Lore and Meaning, Dover Publications, p. 155, ISBN ((978-0486210797)), https://archive.org/details/starnamestheirlo00alle/page/155
- ↑ Script error: The function "in_lang" does not exist. 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- ↑ Script error: The function "in_lang" does not exist. AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 6 日
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