Sigma Cassiopeiae

Sigma Cassiopeiae (σ Cas, σ Cassiopeiae) is a binary star in the constellation Cassiopeia. It is approximately 5000 light years from Earth[1] and has a combined apparent magnitude of +4.88.

σ Cassiopeiae

σ Cassiopeiae in optical light
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cassiopeia
Right ascension  23h 59m 00.538s[1]
Declination +55° 45′ 17.74″[1]
Apparent magnitude (V) +4.88[2] (5.01 + 7.24[3])
Characteristics
Spectral type B2 IV + B3 V[4]
U−B color index −0.82
B−V color index −0.07
Variable type β Cep?[5]
Astrometry
Radial velocity (Rv)−12.6[6] km/s
Proper motion (μ) RA: 8.14 ± 0.34[1] mas/yr
Dec.: −5.01 ± 0.32[1] mas/yr
Parallax (π)0.72 ± 0.43[1] mas
Distanceapprox. 5,000 ly
(approx. 1,400 pc)
Absolute magnitude (MV)−3.90[5] + −1.7[4]
Details[5]
A
Mass12 M☉
Radius11.3 R☉
Luminosity25,000 L☉
Surface gravity (log g)3.6 cgs
Temperature21,000 K
Rotational velocity (v sin i)170 km/s
Age15.8 Myr
Other designations
8 Cassiopeiae, HR 9071, HD 224572, BD+54°3082, HIP 118243, SAO 35947, ADS 17140, CCDM J23591+5546
Database references
SIMBADdata
Map of the Bayer-designated stars in Cassiopeia. Sigma Cassiopeiae is circled.

The primary component, σ Cassiopeiae A, is a B2 subgiant with an apparent magnitude of +5.0. Its companion, σ Cassiopeiae B, is a B5 main sequence dwarf with an apparent magnitude of +7.1. The two stars are three arcseconds apart.[7]

Naming

In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent, refers to an asterism consisting of σ Cassiopeiae, α Lacertae, 4 Lacertae, π2 Cygni, π1 Cygni, HD 206267, ε Cephei, β Lacertae, ρ Cassiopeiae, τ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, λ Andromedae, κ Andromedae, ι Andromedae, and ψ Andromedae. Consequently, the Chinese name for σ Cassiopeiae itself is 螣蛇十一 (Téng Shé shíyī, English: the Eleventh Star of Flying Serpent).[8]

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References
  1. 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.Vizier catalog entry
  2. Nicolet, B. (1978). "Catalogue of homogeneous data in the UBV photoelectric photometric system". Astronomy and Astrophysics. 34: 1. Bibcode:1978A&AS...34....1N.
  3. 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.
  4. Abt, H. A.; Cardona, O. (1983). "Confirmation among visual multiples of an increase of AP stars with age". Astrophysical Journal. 272: 182. Bibcode:1983ApJ...272..182A. doi:10.1086/161276.
  5. Catanzaro, G.; Ventura, R.; Ferrara, F.; Paternò, L. (2010). "Spectroscopic analysis of the candidate β Cephei star σ Cas: Atmospheric characterization and line-profile variability". New Astronomy. 15: 39. Bibcode:2010NewA...15...39C. doi:10.1016/j.newast.2009.05.001.
  6. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  7. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  8. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 7 日
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