12 Comae Berenices

12 Comae Berenices is a binary star system in the northern constellation of Coma Berenices. It is the brightest member of the Coma Cluster and is visible to the naked eye with an apparent visual magnitude of 4.80.[2] Although listed as a suspected variable star, there is no photometric evidence of it being variable in luminosity. However, the radial velocity was found to be variable, as announced by W. W. Campbell in 1910. The first orbital solution was published by Vinter Hansen in the 1940s.[2] It is a double-lined spectroscopic binary with an orbital period of 396.5 days and an eccentricity of 0.566.[6]

12 Comae Berenices

12 Comae Berenices in optical light
Observation data Epoch 2000.0      Equinox 2000.0
Constellation	Coma Berenices
Right ascension	12^h 22^m 30.31076^s[1]
Declination	+25° 50′ 46.1896″[1]
Apparent magnitude (V)	4.80[2]
Characteristics
Spectral type	F6 III + A3 V[3]
U−B color index	0.47/0.09[2]
B−V color index	0.82/0.11[2]
Astrometry
Radial velocity (Rv)	+0.5±0.9[4] km/s
Proper motion (μ)	RA: −10.847[1] mas/yr Dec.: −9.546[1] mas/yr
Parallax (π)	11.8280 ± 0.2353[1] mas
Distance	276 ± 5 ly (85 ± 2 pc)
Absolute magnitude (MV)	0.55±0.06 / 1.05±0.06[2]
Orbit[5][6]
Period (P)	396.54±0.12 d
Eccentricity (e)	0.566±0.050
Inclination (i)	66±2[2]°
Periastron epoch (T)	2444502.4±8.0 JD
Argument of periastron (ω) (secondary)	95.5±3.5°
Semi-amplitude (K1) (primary)	22.42±2.22 km/s
Details[2]
12 Com A
Mass	2.6±0.2 M☉
Radius	8.9±0.8 R☉
Luminosity	56.2+2.7 −2.5 L☉
Temperature	5,300±200 K
Age	670 Myr
12 Com B
Mass	2.05±0.2 M☉
Radius	2.5±0.3 R☉
Luminosity	30.2+2.2 −2.2 L☉
Temperature	8,500±500 K
Other designations
12 Com, NSV 5581, BD+26°2337, FK5 1318, HD 107700, HIP 60351, HR 4707, SAO 82273, WDS J12225+2551A[7]
Database references
SIMBAD	data

This system consists of two stars, an evolved F-type giant star and a smaller but higher temperature A-type main-sequence star.[3] Griffin and Griffin (2011) suggested that the secondary component may have begun its evolution away from the main sequence, and instead assigned it a luminosity class of IV. The primary, designated component A, has 2.6 times the mass of the Sun and has expanded to 8.9 times the Sun's radius. It is radiating 56 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,300 K. Its companion, component B, has double the Sun's mass and 2.5 times the radius. It shines with 30 times the luminosity of the Sun at 8,500 K.[2]

References

1. 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.
2. Griffin, R. E. M.; Griffin, R. F. (February 2011), "Composite spectra: XVII. 12 Comae, a member of the Coma open cluster", Astronomische Nachrichten, 332 (2): 105–115, Bibcode:2011AN....332..105G, doi:10.1002/asna.201011514
3. Abt, Helmut A. (2008). "Visual Multiples. IX. MK Spectral Types". The Astrophysical Journal Supplement Series. 176: 216–217. Bibcode:2008ApJS..176..216A. doi:10.1086/525529.
4. Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. 30. University of Toronto: International Astronomical Union. p. 57. Bibcode:1967IAUS...30...57E.
5. Pourbaix, D.; et al. (2004). "S_B⁹: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213.
6. Mermilliod, J. -C; et al. (2007). "Red giants in open clusters. XIII. Orbital elements of 156 spectroscopic binaries". Astronomy and Astrophysics. 473 (3): 829. Bibcode:2007A&A...473..829M. doi:10.1051/0004-6361:20078007.
7. "12 Com". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved December 30, 2018.