Beta Comae Berenices
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 Location of β Coma Bernices (upper left) |
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| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Coma Berenices |
| Right ascension | 13h 11m 52.39379s[1] |
| Declination | +27° 52′ 41.4535″[1] |
| Apparent magnitude (V) | 4.26 |
| Characteristics | |
| Spectral type | G0V[2] |
| U−B color index | 0.07 |
| B−V color index | 0.57[3] |
| Variable type | None |
| Astrometry | |
| Radial velocity (Rv) | +6.1[4] km/s |
| Proper motion (μ) | RA: -801.44[1] mas/yr Dec.: 882.04[1] mas/yr |
| Parallax (π) | 109.54 ± 0.17[1] mas |
| Distance | 29.78 ± 0.05 ly (9.13 ± 0.01 pc) |
| Absolute magnitude (MV) | 4.45 |
| Details | |
| Mass | 1.15[5] M☉ |
| Radius | 1.09[5] R☉ |
| Surface gravity (log g) | 4.38[3] |
| Temperature | 6,029[3] K |
| Metallicity [Fe/H] | +0.07[3] dex |
| Rotational velocity (v sin i) | 4.10 ± 0.06[6] km/s |
| Age | 1.5–2.5[7] Gyr |
| Other designations | |
Beta Comae Berenices (β Comae Berenices, β Com) is a main sequence dwarf star in the constellation of Coma Berenices. It is located at a distance of about 30 light years. The Greek letter beta (β) usually indicates that the star has the second highest visual magnitude in the constellation. However, this star is slightly brighter than α Comae Berenices.
This star is similar to our own Sun, being only slightly larger and brighter in absolute magnitude. Observations of short term variations in the chromatic activity suggest that the star undergoes differential rotation,[8] with a rotation period of about 11–13 days.[6] Its surface has a measured activity cycle of 16.6 years, compared to 11 years on our Sun. It may also have a secondary activity cycle of 9.6 years.[9] At one time it was thought that this star might have a spectroscopic companion. However, this was ruled out by means of more accurate radial velocity measurements. No planets have yet been detected around it, and there is no evidence of a dusty disk.
[edit] References
- ^ a b c d e van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752v1, Bibcode 2007A&A...474..653V, doi:10.1051/0004-6361:20078357 Note: see VizieR catalogue I/311.
- ^ Gray, R. O.; Napier, M. G.; Winkler, L. I. (April 2001), "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars", The Astronomical Journal 121 (4): 2148–2158, Bibcode 2001AJ....121.2148G, doi:10.1086/319956
- ^ a b c d Mallik, Sushma V. (October 1998). "Chromospheric activity in cool stars and the lithium abundance". Astronomy and Astrophysics 338: 623–636. Bibcode 1998A&A...338..623M.
- ^ Wilson, Ralph Elmer (1953). General Catalogue of Stellar Radial Velocities. Washington: Carnegie Institution of Washington. Bibcode 1953QB901.W495......
- ^ a b Takeda, G. et al. (2007). "Stellar parameters of nearby cool stars. II. Physical properties of ~1000 cool stars from the SPOCS catalog". Astrophysical Journal Supplement Series 168: 297–318. Bibcode 2008yCat..21680297T. Note: see VizieR catalogue J/ApJS/168/297.
- ^ a b Gray, David F.; Baliunas, Sallie L. (January 1997), "The Rotation of the G0 Dwarf beta Comae", Astrophysical Journal 475: 303–312, Bibcode 1997ApJ...475..303G, doi:10.1086/303522
- ^ Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008). "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics". The Astrophysical Journal 687 (2): 1264–1293. Bibcode 2008ApJ...687.1264M. doi:10.1086/591785.
- ^ Donahue, Robert A.; Baliunas, Sallie L. (July 1992), "Evidence of differential surface rotation in the solar-type star HD 114710", Astrophysical Journal, Part 2 - Letters 393 (2): L63-L66, Bibcode 1992ApJ...393L..63D, doi:10.1086/186452
- ^ Baliunas, S. L. et al. (January 1995), "Chromospheric variations in main-sequence stars", Astrophysical Journal, Part 1 438 (1): 269–287, Bibcode 1995ApJ...438..269B, doi:10.1086/175072 See appendix A.
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