Sigma Cassiopeiae

Sigma Cassiopeiae (σ Cas, σ Cassiopeiae) is a binary star in the constellation Cassiopeia. It is 1,200 to 1,400 light years from Earth and has a combined apparent magnitude of +4.88.[7]

Not to be confused with S Cassiopeiae.
σ Cassiopeiae
Location of σ Cassiopeiae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cassiopeia
σ Cas A
Right ascension 23h 59m 00.538s[1]
Declination +55° 45′ 17.75″[1]
Apparent magnitude (V) 5.01[2]
σ Cas B
Right ascension 23h 59m 00.331s[3]
Declination +55° 45′ 20.37″[3]
Apparent magnitude (V) 7.24[2]
Characteristics
σ Cas A
Spectral type B2 IV[4]
U−B color index −0.82
B−V color index −0.07
Variable type β Cep?[5]
σ Cas B
Spectral type B3 V[4]
Astrometry
σ Cas A
Radial velocity (Rv)−12.6[6] km/s
Proper motion (μ) RA: +9.956[1] mas/yr
Dec.: −4.492[1] mas/yr
Parallax (π)2.7419 ± 0.1491 mas[1]
Distance1,190 ± 60 ly
(360 ± 20 pc)
Absolute magnitude (MV)−3.90[5]
Radial velocity (Rv)−5.0[6] km/s
Proper motion (μ) RA: +8.651[3] mas/yr
Dec.: −3.739[3] mas/yr
Parallax (π)2.2572 ± 0.0558 mas[3]
Distance1,440 ± 40 ly
(440 ± 10 pc)
Absolute magnitude (MV)−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
σ Cassiopeiae in optical light

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.[8]

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).[9]

References
  1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. 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.
  3. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  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 (1): 39. Bibcode:2010NewA...15...39C. doi:10.1016/j.newast.2009.05.001.
  6. Kharchenko, N.V.; Scholz, R.-D.; Piskunov, A.E.; Röser, S.; Schilbach, E. (November 2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889–896. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. eISSN 1521-3994. ISSN 0004-6337. S2CID 119323941.
  7. Nicolet, B. (1978). "Catalogue of homogeneous data in the UBV photoelectric photometric system". Astronomy and Astrophysics. 34: 1. Bibcode:1978A&AS...34....1N.
  8. 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.
  9. (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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