Editing Variable star (section)

=====FK Comae Berenices variables=====
[[File:FKComLightCurve.png|thumb|right|[[Light curve]]s for FK Comae Berenices. The main plot shows the short term variability plotted from [[Transiting Exoplanet Survey Satellite|''TESS'']] data;<ref name=MAST/> the inset, adapted from Panov and Dimitrov (2007),<ref name="Panov"/> shows the long term variability.]]
These stars rotate extremely rapidly (~100&nbsp;km/s at the [[equator]]); hence they are [[ellipsoidal]] in shape. They are (apparently) single giant stars with [[spectral type]]s G and K and show strong [[chromosphere|chromospheric]] [[emission line]]s. Examples are [[FK Comae Berenices|FK Com]], [[V1794 Cygni]] and [[UZ Librae]]. A possible explanation for the rapid rotation of FK Comae stars is that they are the result of the merger of a [[contact binary|(contact) binary]].<ref name=Livio_Stoker_1988>{{cite journal
 | title=The Common Envelope Phase in the Evolution of Binary Stars
 | last1=Livio | first1=Mario | last2=Soker | first2=Noam
 | journal=Astrophysical Journal | volume=329 | page=764
 | date=June 1988 | doi=10.1086/166419 | bibcode=1988ApJ...329..764L
}}</ref><!-- Ref. for last statement. -->