Theta Cephei

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Theta Cephei
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cepheus
Right ascension 20h 29m 34.86518s[1]
Declination +62° 59′ 38.6216″[1]
Apparent magnitude (V) 4.22[2]
Characteristics
Spectral type A7 III[3] or Am (A7/F1/F2)[4]
U−B color index +0.16[2]
B−V color index +0.20[2]
Astrometry
Radial velocity (Rv)−6.8[5] km/s
Proper motion (μ) RA: 52.416[1] mas/yr
Dec.: −2.544[1] mas/yr
Parallax (π)25.7611 ± 0.5808[1] mas
Distance127 ± 3 ly
(38.8 ± 0.9 pc)
Absolute magnitude (MV)+1.12[6]
Orbit[7]
Period (P)914.3±7.0 d
Eccentricity (e)0.377 ± 0.006
Periastron epoch (T)2456991.3 ± 8.5 JD
Argument of periastron (ω)
(primary)		48.8 ± 1.1°
Semi-amplitude (K1)
(primary)		7.72 ± 0.06 km/s
Details
θ Cep A
Radius3.09+0.36
−0.25[1] R☉
Luminosity25.37±0.66[1] L☉
Surface gravity (log g)3.74[3] cgs
Temperature7,375+307
−404[1] K
Metallicity [Fe/H]+0.27±0.04[6] dex
Rotational velocity (v sin i)52.0[3] km/s
Other designations
θ Cep, 2 Cep, BD+62° 1821, FK5 767, HD 195725, HIP 101093, HR 7850, SAO 18897[8]
Database references
SIMBADdata

Theta Cephei, Latinized from θ Cephei, is a stellar class A7, fourth-magnitude star in the constellation Cepheus. This displays at a metallic-line Am star.[4] It is a white-hued, single-lined spectroscopic binary system, located about 127 light-years from Earth. The pair have an orbital period of 2.5 years;[7] the eccentricity was long thought to be low, at 0.03,[9] but recent calculations have put it at a much higher 0.377.[7] They are separated by 4.16 AU.[10]

Shared with η Cep, this star system has the title Al Kidr,[11] although the meaning of this name is unknown. In Chinese, 天鈎 (Tiān Gōu), meaning Celestial Hook, refers to an asterism consisting of , , η Cephei, α Cephei, ξ Cephei, , ι Cephei and ο Cephei.[12] Consequently, the Chinese name for θ Cephei itself is 天鈎三 (Tiān Gōu sān, English: the Third Star of Celestial Hook.).[13]

References[]

  1. ^ a b c d e f g h Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. ^ a b c 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.
  3. ^ a b c 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, arXiv:1111.1603, Bibcode:2012PASJ...64...38T, doi:10.1093/pasj/64.2.38, 38
  4. ^ a b 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, Bibcode:1995ApJS...99..135A, doi:10.1086/192182.
  5. ^ 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.
  6. ^ a b 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, S2CID 119257644.
  7. ^ a b c Bischoff, Richard; Mugrauer, Markus; Lux, Oliver; Zehe, Tamara; Heyne, Therese; Wagner, Daniel; Geymeier, Michael (2020). "Spectroscopic orbit determination of the long‐periodic binary system θ Cep". Astronomische Nachrichten. 341 (10): 989–995. doi:10.1002/asna.202013850. S2CID 229394315.
  8. ^ "tet Cep". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-05-06.CS1 maint: postscript (link)
  9. ^ Abt, Helmut A. (March 1961), "The Frequency of Binaries among Metallic-Line Stars", Astrophysical Journal Supplement, 6: 37, Bibcode:1961ApJS....6...37A, doi:10.1086/190060.
  10. ^ Trilling, D. E.; et al. (April 2007), "Debris disks in main-sequence binary systems", The Astrophysical Journal, 658 (2): 1264–1288, arXiv:astro-ph/0612029, Bibcode:2007ApJ...658.1289T, doi:10.1086/511668, S2CID 14867168
  11. ^ Allen, Richard Hinckley (1963-06-01). Star Names: Their Lore and Meaning. Dover Publications. p. 155. ISBN 978-0486210797.
  12. ^ (in Chinese) 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.
  13. ^ (in Chinese) 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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