# FK Comae Berenices

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Star in the constellation of Coma Berenices

FK Comae Berenices Light curves for FK Comae Berenices. The main plot shows the short term variability plotted from TESS data;[1] the inset, adapted from Panov and Dimitrov (2007),[2] shows the long term variability. Observation data Epoch J2000 Equinox J2000 Constellation Coma Berenices Right ascension 13h 30m 46.79937s[3] Declination +24° 13′ 57.7862″[3] Apparent magnitude (V) 8.14 – 8.33[4] Characteristics Evolutionary stage red giant branch[5] Spectral type G4 III[6] Variable type FK Com[4] Astrometry Radial velocity (Rv) −21.0±5.8[6] km/s Proper motion (μ) RA: −51.969[3] mas/yr Dec.: −22.262[3] mas/yr Parallax (π) 4.6102±0.0446 mas[3] Distance 707 ± 7 ly (217 ± 2 pc) Absolute magnitude (MV) 1.2[7] Details Mass 1.1[8] M☉ Radius 6.99[3] R☉ Luminosity 26.8[3] L☉ Surface gravity (log g) 2.359[9] cgs Temperature 4,966[3] K Metallicity [Fe/H] −0.89[8] dex Rotation 2.4 days[10] Rotational velocity (v sin i) 160[11] km/s Other designations BD+24°2592, HD 117555, HIP 65915, SAO 82867[12] Database references SIMBAD data

**FK Comae Berenices** is a [variable star](/source/Variable_star) that varies in [apparent magnitude](/source/Apparent_magnitude) between 8.14 and 8.33 over a period of 2.4 days. In 1966, Pavel Fedorovich Chugainov discovered that the star, then called HD 117555, varied in brightness.[13] It was given its [variable star designation](/source/Variable_star_designation), FK Comae Berenices, in 1968.[14] It is the prototype for the [FK Comae Berenices](/source/Variable_star#FK_Comae_Berenices_variables) (FK Com) class of variable stars. The variability of FK Com stars may be caused by large, cool spots on the rotating surfaces of the stars. This star is thought to be the result of a recent binary merger, resulting in a high rate of both spin and [magnetic activity](/source/Magnetic_activity).

The spectral class of FK Comae Berenices is G4 III, although it is considered unusual in having very broad [absorption lines](/source/Absorption_line) as well as some [emission lines](/source/Emission_line). The broadened spectral lines are due to rapid rotation.[11]

The rotation rate of FK Comae Berenices is unusually fast for a cool [giant star](/source/Giant_star). It is speculated that this is due to the merger of a contact binary pair of stars into a single star. The rotation produces extremely strong magnetic fields which are expected to [brake](/source/Magnetic_braking_(astronomy)) the star to a slower rotation rate. Analysis of variability due to star spots on the surface show that the star rotates at different speeds at different latitudes.[10]

FK Comae Berenices is listed as a companion to the slightly brighter HD 117567. The two are not thought to be physically associated, with HD 117567 being a much closer F2 [main sequence](/source/Main_sequence) star.[15]

## References

1. **[^](#cite_ref-MAST_1-0)** ["MAST: Barbara A. Mikulski Archive for Space Telescopes"](https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html). Space Telescope Science Institute. Retrieved 8 December 2021.

1. **[^](#cite_ref-Panov_2-0)** Panov, K.; Dimitrov, D. (May 2007). ["Long-term photometric study of FK Comae Berenices and HD 199178"](https://doi.org/10.1051%2F0004-6361%3A20065596). *Astronomy and Astrophysics*. **467**: 229–235. [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20065596](https://doi.org/10.1051%2F0004-6361%3A20065596).

1. ^ [***a***](#cite_ref-GaiaDR2_3-0) [***b***](#cite_ref-GaiaDR2_3-1) [***c***](#cite_ref-GaiaDR2_3-2) [***d***](#cite_ref-GaiaDR2_3-3) [***e***](#cite_ref-GaiaDR2_3-4) [***f***](#cite_ref-GaiaDR2_3-5) [***g***](#cite_ref-GaiaDR2_3-6) [***h***](#cite_ref-GaiaDR2_3-7) [Brown, A. G. A.](/source/Anthony_Brown_(scientist)); et al. ([Gaia collaboration](/source/Data_Processing_and_Analysis_Consortium)) (August 2018). ["*Gaia* Data Release 2: Summary of the contents and survey properties"](https://doi.org/10.1051%2F0004-6361%2F201833051). *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. **616**. A1. [arXiv](/source/ArXiv_(identifier)):[1804.09365](https://arxiv.org/abs/1804.09365). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...616A...1G](https://ui.adsabs.harvard.edu/abs/2018A&A...616A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201833051](https://doi.org/10.1051%2F0004-6361%2F201833051). [Gaia DR2 record for this source](https://vizier.u-strasbg.fr/viz-bin/VizieR-S?Gaia%20DR2%203937690377058804480) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-gcvs_4-0) [***b***](#cite_ref-gcvs_4-1) Samus, N. N.; Durlevich, O. V.; et al. (2009), "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)", *VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S*, **1**: B/GCVS, [Bibcode](/source/Bibcode_(identifier)):[2009yCat....102025S](https://ui.adsabs.harvard.edu/abs/2009yCat....102025S).

1. **[^](#cite_ref-gondoin2002_5-0)** Gondoin, P.; Erd, C.; Lumb, D. (2002). "Structure and evolution of FK Comae corona". *Astronomy and Astrophysics*. **383** (3): 919. [Bibcode](/source/Bibcode_(identifier)):[2002A&A...383..919G](https://ui.adsabs.harvard.edu/abs/2002A&A...383..919G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20011810](https://doi.org/10.1051%2F0004-6361%3A20011810).

1. ^ [***a***](#cite_ref-Strassmeier2009_6-0) [***b***](#cite_ref-Strassmeier2009_6-1) Strassmeier, Klaus G. (September 2009), "Starspots", *[The Astronomy and Astrophysics Review](/source/The_Astronomy_and_Astrophysics_Review)*, **17** (3): 251–308, [Bibcode](/source/Bibcode_(identifier)):[2009A&ARv..17..251S](https://ui.adsabs.harvard.edu/abs/2009A&ARv..17..251S), [doi](/source/Doi_(identifier)):[10.1007/s00159-009-0020-6](https://doi.org/10.1007%2Fs00159-009-0020-6).

1. **[^](#cite_ref-korhonen1999_7-0)** Korhonen, H.; Berdyugina, S. V.; Hackman, T.; Duemmler, R.; Ilyin, I. V.; Tuominen, I. (1999), "Study of FK Comae Berenices. I. Surface images for 1994 and 1995", *[Astronomy and Astrophysics](/source/Astronomy_and_Astrophysics)*, **346**: 103, [Bibcode](/source/Bibcode_(identifier)):[1999A&A...346..101K](https://ui.adsabs.harvard.edu/abs/1999A&A...346..101K).

1. ^ [***a***](#cite_ref-starhorse_8-0) [***b***](#cite_ref-starhorse_8-1) Anders, F.; Khalatyan, A.; Chiappini, C.; Queiroz, A. B.; Santiago, B. X.; Jordi, C.; Girardi, L.; Brown, A. G. A.; Matijevič, G.; Monari, G.; Cantat-Gaudin, T.; Weiler, M.; Khan, S.; Miglio, A.; Carrillo, I.; Romero-Gómez, M.; Minchev, I.; De Jong, R. S.; Antoja, T.; Ramos, P.; Steinmetz, M.; Enke, H. (2019), "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18", *Astronomy and Astrophysics*, **628**: A94, [arXiv](/source/ArXiv_(identifier)):[1904.11302](https://arxiv.org/abs/1904.11302), [Bibcode](/source/Bibcode_(identifier)):[2019A&A...628A..94A](https://ui.adsabs.harvard.edu/abs/2019A&A...628A..94A), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201935765](https://doi.org/10.1051%2F0004-6361%2F201935765), [S2CID](/source/S2CID_(identifier)) [131780028](https://api.semanticscholar.org/CorpusID:131780028).

1. **[^](#cite_ref-mcdonald2017_9-0)** McDonald, I.; Zijlstra, A. A.; Watson, R. A. (2017), "Fundamental parameters and infrared excesses of Tycho–Gaia stars", *Monthly Notices of the Royal Astronomical Society*, **471** (1): 770–791, [arXiv](/source/ArXiv_(identifier)):[1706.02208](https://arxiv.org/abs/1706.02208), [Bibcode](/source/Bibcode_(identifier)):[2017MNRAS.471..770M](https://ui.adsabs.harvard.edu/abs/2017MNRAS.471..770M), [doi](/source/Doi_(identifier)):[10.1093/mnras/stx1433](https://doi.org/10.1093%2Fmnras%2Fstx1433).

1. ^ [***a***](#cite_ref-hackman2013_10-0) [***b***](#cite_ref-hackman2013_10-1) Hackman, T.; Pelt, J.; Mantere, M. J.; Jetsu, L.; Korhonen, H.; Granzer, T.; Kajatkari, P.; Lehtinen, J.; Strassmeier, K. G. (2013), "Flip-flops of FK Comae Berenices", *Astronomy & Astrophysics*, **553**: A40, [arXiv](/source/ArXiv_(identifier)):[1211.0914](https://arxiv.org/abs/1211.0914), [Bibcode](/source/Bibcode_(identifier)):[2013A&A...553A..40H](https://ui.adsabs.harvard.edu/abs/2013A&A...553A..40H), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201220690](https://doi.org/10.1051%2F0004-6361%2F201220690), [S2CID](/source/S2CID_(identifier)) [118705220](https://api.semanticscholar.org/CorpusID:118705220).

1. ^ [***a***](#cite_ref-Ayres2016_11-0) [***b***](#cite_ref-Ayres2016_11-1) Ayres, Thomas R.; et al. (March 2016), "FK Comae Berenices, King of Spin: The COCOA-PUFS Project", *[The Astrophysical Journal Supplement Series](/source/The_Astrophysical_Journal_Supplement_Series)*, **223** (1): 30, [arXiv](/source/ArXiv_(identifier)):[1601.03305](https://arxiv.org/abs/1601.03305), [Bibcode](/source/Bibcode_(identifier)):[2016ApJS..223....5A](https://ui.adsabs.harvard.edu/abs/2016ApJS..223....5A), [doi](/source/Doi_(identifier)):[10.3847/0067-0049/223/1/5](https://doi.org/10.3847%2F0067-0049%2F223%2F1%2F5), [S2CID](/source/S2CID_(identifier)) [118501523](https://api.semanticscholar.org/CorpusID:118501523), 5.

1. **[^](#cite_ref-SIMBAD_12-0)** ["FK Com"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=FK+Com). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2019-01-06.

1. **[^](#cite_ref-Chugainov1966_13-0)** Chugainov, P. F. (December 1966). ["New Microvariable HD 117555"](https://ibvs.konkoly.hu/pub/ibvs/0101/0172.pdf) (PDF). *Information Bulletin on Variable Stars*. **172**: 1–2. [Bibcode](/source/Bibcode_(identifier)):[1966IBVS..172....1C](https://ui.adsabs.harvard.edu/abs/1966IBVS..172....1C). Retrieved 28 January 2025.

1. **[^](#cite_ref-Kukarkin1968_14-0)** Kukarkin, B. V.; Efremov, Yu. N.; Frolov, M. S.; Medvedeva, G. I.; Kholopov, P. N.; Kurochkin, N. E.; Kukarkina, N. P.; Perova, N. B.; Fedorovich, V. P. (November 1968). ["Identification List of the New Variable Stars Nominated in 1968"](https://ibvs.konkoly.hu/pub/ibvs/0301/0311.pdf) (PDF). *Information Bulletin on Variable Stars*. **311**. [Bibcode](/source/Bibcode_(identifier)):[1968IBVS..311....1K](https://ui.adsabs.harvard.edu/abs/1968IBVS..311....1K). Retrieved 28 January 2025.

1. **[^](#cite_ref-wds_15-0)** 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](/source/Bibcode_(identifier)):[2001AJ....122.3466M](https://ui.adsabs.harvard.edu/abs/2001AJ....122.3466M), [doi](/source/Doi_(identifier)):[10.1086/323920](https://doi.org/10.1086%2F323920).

## External links

- [FK Coma Berenices](http://jumk.de/astronomie/special-stars/fk-comae-berenices.shtml)

v t e Constellation of Coma Berenices List of stars in Coma Berenices Coma Berenices in Chinese astronomy Stars Bayer α (Diadem) β γ Flamsteed 7 11 12 13 14 16 17 21 23 (Phyllon Kissinou) 24 31 35 36 37 41 Variable FK GP IN LW HR 4668 HD 107146 108863 108874 110067 114762 b 115404 116029 Other 2MASS J12195156+3128497 KELT-6 WASP-56 WISE 1217+1626 Exoplanets HD 108874 b c KELT-6b Star clusters Coma Star Cluster Messier 53 NGC 4147 NGC 5053 Nebulae LoTr 5 Galaxies Messier 64 (Black Eye Galaxy) 85 88 91 98 99 100 NGC 4014 4015 4017 4053 4056 4060 4061 4065 4066 4070 4072 4074 4076 4084 4086 4089 4090 4091 4092 4093 4095 4098 4136 4146 4150 4162 4185 4189 4203 4211 4212 4213 4222 4237 4245 4253 4262 4274 4278 4293 4298 4302 4308 4310 4312 4314 4323 4328 4340 4359 4375 4383 4393 4394 4414 4419 4448 4450 4455 4459 4468 4473 4474 4475 4477 4479 4489 4494 4495 4498 4502 4506 4515 4516 4523 4525 4540 4555 4556 4558 4559 4561 4565 4571 4585 4595 4611 4614 4615 4633 4634 4651 4659 4670 4673 4676 (Mice Galaxies) 4689 4692 4710 4712 4725 4747 4839 4848 4860 4869 4871 4872 4873 4874 4875 4876 4881 4883 4886 4889 4892 4895 4907 4911 4919 4921 4944 5000 5004 5012 5032 5056 5172 Other 3C 275.1 3C 287 Arp 60 Coma Berenices Dragonfly 44 IC 755 (NGC 4019) IC 831 IC 860 IC 3505 IC 3528 IC 4040 IC 4051 IOK-1 IRAS F12032+1707 LEDA 83677 M85-HCC1 Malin 1 PGC 44691 PKS 1155+251 PKS 1222+216 VIRGOHI21 ZwCl 1305.4+2941 BCG Galaxy clusters Abell 1413 Coma I Coma Cluster Coma Supercluster M94 Group NGC 4065 Group NGC 4631 Group Astronomical events GRB 050509B iPTF14atg SN 1940B SN 1979C SN 2005ap SN 2006X SN 2020oi Category

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Adapted from the Wikipedia article [FK Comae Berenices](https://en.wikipedia.org/wiki/FK_Comae_Berenices) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/FK_Comae_Berenices?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.