FK Comae 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
Spectral type G4 III[5]
Variable type FK Com[4]
Astrometry
Radial velocity (Rv)−21.0±5.8[5] 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]
Distance707 ± 7 ly
(217 ± 2 pc)
Absolute magnitude (MV)1.2[6]
Details
Mass1.1[7] M☉
Radius6.99[3] R☉
Luminosity26.8[3] L☉
Surface gravity (log g)2.359[8] cgs
Temperature4,966[3] K
Metallicity [Fe/H]−0.89[7] dex
Rotation2.4 days[9]
Rotational velocity (v sin i)160[10] km/s
Other designations
BD+24°2592, HD 117555, HIP 65915, SAO 82867[11]
Database references
SIMBADdata

FK Comae Berenices is a variable star that varies in apparent magnitude between 8.14 and 8.33 over a period of 2.4 days. It is the prototype for the FK Comae Berenices (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.

The spectral class of FK Comae Berenices is G4 III, although it is considered unusual in having very broad absorption lines as well as some emission lines. The broadened spectral lines are due to rapid rotation.[10]

The rotation rate of FK Comae Berenices is unusually fast for a cool 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 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.[9]

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 star.[12]

  1. ^ Cite error: The named reference MAST was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference Panov was invoked but never defined (see the help page).
  3. ^ a b c d e f g h Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference gcvs was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Strassmeier2009 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference korhonen1999 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference starhorse was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference mcdonald2017 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference hackman2013 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Ayres2016 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference wds was invoked but never defined (see the help page).