31 Comae Berenices

31 Comae Berenices (31 Com) is a yellow giant star in the constellation Coma Berenices. Its apparent magnitude is about 4.9 and slightly variable. It is visible to the naked eye. In 1997, Klaus G. Strassmeier et al. announced their discovery that the star is a variable star.^[1] It was given its variable star designation, LS Comae Berenices, in 2003.^[7] It is a rare FK Comae Berenices variable, a variable star that spins rapidly and has large starspots on its surface.^[6] It is currently in the Hertzsprung gap and its outer envelope has just begun convection.^[4] In 1989 it was given as a spectral standard for the class G0IIIp.^[8]

31 Comae Berenices

A visual band light curve for 31 Comae Berenices, adapted from Strassmeier et al. (1997).[1] The red line shows the linear least squares fit to the data.
Observation data Epoch J2000      Equinox J2000
Constellation	Coma Berenices
Right ascension	12h 51m 41.91900s[2]
Declination	+27° 32′ 26.5683″[2]
Apparent magnitude (V)	4.87 - 4.97[3]
Characteristics
Evolutionary stage	Hertzsprung gap[4]
Spectral type	G0III[5]
Variable type	FK Com[3]
Astrometry
Proper motion (μ)	RA: −10.990[2] mas/yr Dec.: −8.313[2] mas/yr
Parallax (π)	11.4933 ± 0.1828 mas[2]
Distance	284 ± 5 ly (87 ± 1 pc)
Details[5]
Radius	8.9 R☉
Luminosity	74 L☉
Surface gravity (log g)	3.51 cgs
Temperature	5,660 K
Metallicity [Fe/H]	−0.15 dex
Rotation	6.8 d
Rotational velocity (v sin i)	67 km/s
Other designations
31 Com, LS Comae Berenices, BD+28°2156, FK5 1332, HD 111812, HIP 62763, HR 4883, SAO 82537[6]
Database references
SIMBAD	data

31 Com is the north galactic pole star, and occasionally goes by the informal name Polaris Galacticum Borealis, coined by Jim Kaler.^[9]

In Chinese astronomy, 31 Comae Berenices is called 郎將, Pinyin: Lángjiāng, meaning Captain of the Bodyguards, because this star is marking itself and stand alone in Captain of the Bodyguards asterism, Supreme Palace enclosure mansion (see : Chinese constellation).^[10]

References

1. Strassmeier, K. G.; Bartus, J.; Cutispoto, G.; Rodono, M. (October 1997). "Starspot photometry with robotic telescopes: Continuous UBV and V(RI)_C photometry of 23 stars in 1991-1996" (PDF). Astronomy & Astrophysics Supplement Series. 125: 11–63. Bibcode:1997A&AS..125...11S. doi:10.1051/aas:1997369. Retrieved 29 January 2025.
2. 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.
3. Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
4. Strassmeier, K. G.; et al. (September 2010), "Rotation and magnetic activity of the Hertzsprung-gap giant 31 Comae", Astronomy and Astrophysics, 520: 14, Bibcode:2010A&A...520A..52S, doi:10.1051/0004-6361/201015023, A52.
5. Aurière, M.; et al. (February 2015), "The magnetic fields at the surface of active single G-K giants", Astronomy & Astrophysics, 574: 30, arXiv:1411.6230, Bibcode:2015A&A...574A..90A, doi:10.1051/0004-6361/201424579, S2CID 118504829, A90.
6. "31 Com". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 13, 2018.
7. Kazarovets, E. V.; Kireeva, N. N.; Samus, N. N.; Durlevich, O. V. (May 2003). "The 77th Name-List of Variable Stars" (PDF). Information Bulletin on Variable Stars. 5422: 1–56. Bibcode:2003IBVS.5422....1K. Retrieved 29 January 2025.
8. Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins Catalog of Revised MK Types for the Cooler Stars", The Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373
9. "Polaris Galacticum Borealis". Retrieved 2015-12-02.
10. Ian Ridpath's Startales - Coma Berenices the Berenice's Hair