Theta Cephei

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Theta Cephei
Observation data
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 kA7hF1mF2[4][5]
U−B color index +0.16[2]
B−V color index +0.20[2]
Distance
127 ± 3 ly
(38.8 ± 0.9 pc)
Absolute magnitude (MV)+1.12[7]
Semi-amplitude
(K1)
(primary)		7.72±0.06 km/s
Details
primary
Myr
companion
Mass>0.62[8] M☉
Radius0.654+0.044
−0.102[8] R☉
Temperature4,070+340
−130[8] K
HR 7850, SAO 18897[10]
Database references
SIMBADdata

Theta Cephei,

spectroscopic binary system, located about 127 light-years from Earth. The pair have an orbital period of 2.5 years;[8] the eccentricity was long thought to be low, at 0.03,[11] but recent calculations have put it at a much higher 0.377.[8] They are separated by 4.16 AU.[12] 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

Chinese name for θ Cephei itself is 天鈎三 (Tiān Gōu sān, English: the Third Star of Celestial Hook.).[15]

References

  1. ^
    doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR
    .
  2. ^
    Bibcode:1966CoLPL...4...99J
    .
  3. ^
    doi:10.1093/pasj/64.2.38
    , 38
  4. ^
    doi:10.1086/192182
    .
  5. Bibcode:2014yCat....1.2023S
    .
  6. Bibcode:1967IAUS...30...57E
    .
  7. ^
    S2CID 119257644
    .
  8. ^
    S2CID 229394315
    .
  9. ^
    S2CID 245837778
    .
  10. ^ "tet Cep", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2017-05-06.
  11. doi:10.1086/190060
    .
  12. S2CID 14867168
    .
  13. ISBN 978-0486210797
  14. ISBN 978-986-7332-25-7
    .
  15. ^ (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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