 Map of the Bayer-designated stars in Cassiopeia. Upsilon Cassiopeiae is circled. | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cassiopeia |
| Right ascension | 00 56 39.90413 |
| Declination | +59° 10′ 51.8006″ |
| Apparent magnitude (V) | +4.62 |
| Characteristics | |
| Evolutionary stage | horizontal branch |
| Spectral type | G8 IIIb Fe−0.5 |
| U−B color index | +0.68 |
| B−V color index | +0.96 |
| Astrometry | |
| Radial velocity (Rv) | −47.73±0.12 km/s |
| Proper motion (μ) | RA: −92.085 mas/yr Dec.: −45.079 mas/yr |
| Parallax (π) | 17.2875 ± 0.1880 mas |
| Distance | 189 ± 2 ly (57.8 ± 0.6 pc) |
| Absolute magnitude (MV) | +0.62 |
| Details | |
| Mass | 1.44±0.16 M☉ |
| Radius | 10.44+0.24 −0.50 R☉ |
| Luminosity | 55.3±0.7 L☉ |
| Surface gravity (log g) | 2.75±0.19 cgs |
| Temperature | 4,937±14 K |
| Metallicity | −0.35±0.03 dex |
| Rotational velocity (v sin i) | 0.54±0.38 km/s |
| Age | 2.20±0.62 Gyr |
| Other designations | |
| Castula, υ Cas, 28 Cassiopeiae, BD+58° 138, HD 5395, HIP 4422, HR 265, SAO 21855 | |
| Database references | |
| SIMBAD | data |
Upsilon Cassiopeiae, Latinised from υ Cassiopeiae, is a solitary star in the constellation of Cassiopeia, a few degrees to the south of Gamma Cassiopeiae. It has the proper name Castula /ˈkæstjʊlə/, which has been officially adopted by the IAU. The star has a yellow hue and is faintly visible to the naked eye with an apparent visual magnitude of +4.62. Based upon parallax measurements, it is located at a distance of approximately 189 light years from the Sun. The star is drifting closer with a radial velocity of −48 km/s.
This is an aging giant star with a stellar classification of G8 IIIb Fe−0.5, where the suffix notation indicates a mild underabundance of iron in the spectrum. With the supply of core hydrogen exhausted, this star has cooled and expanded off the main sequence – at present it has 10 times the girth of the Sun. It is a red clump giant, which means it is on the horizontal branch undergoing core helium fusion.
Upsilon Cassiopeiae is a barium star, showing an excess of the element barium in its spectrum. This can occur from mass transfer from a more-evolved companion star that later became a white dwarf, although no companion has been detected. It is 2.2 billion years old with 1.44 times the mass of the Sun. The star is radiating 55 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,937 K.
Nomenclature
υ Cassiopeiae is the star's Bayer designation. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name Castula for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.
References
- ^ 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.
- ^ Argue, A. N. (1966), "UBV photometry of 550 F, G and K type stars", Monthly Notices of the Royal Astronomical Society, 133 (4): 475, Bibcode:1966MNRAS.133..475A, doi:10.1093/mnras/133.4.475.
- ^ Puzeras, E.; et al. (October 2010), "High-resolution spectroscopic study of red clump stars in the Galaxy: iron-group elements", Monthly Notices of the Royal Astronomical Society, 408 (2): 1225–1232, arXiv:1006.3857, Bibcode:2010MNRAS.408.1225P, doi:10.1111/j.1365-2966.2010.17195.x, S2CID 44228180.
- ^ Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
- ^ Jofré, E.; et al. (2015), "Stellar parameters and chemical abundances of 223 evolved stars with and without planets", Astronomy & Astrophysics, 574: A50, arXiv:1410.6422, Bibcode:2015A&A...574A..50J, doi:10.1051/0004-6361/201424474, S2CID 53666931.
- ^ Bergeat, J.; Knapik, A. (May 1997), "The barium stars in the Hertzsprung-Russel diagram.", Astronomy and Astrophysics, 321: L9, Bibcode:1997A&A...321L...9B.
- ^ Naming Stars, IAU.org, retrieved 16 December 2017
- IAU Working Group on Star Names (WGSN), IAU.org, retrieved 22 May 2016
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