White-Light Flares on Close Binaries Observed with Kepler
(Feb 25, 2016)Abstract
Based on Kepler data, we present the results of a search for white-light
flares on 1049 close binaries. We identify 234 flare binaries, on which 6818
flares are detected. We compare the flare-binary fraction in different binary
morphologies ("detachedness"). The result shows that the fractions in
over-contact and ellipsoidal binaries are approximately 10-20 percent lower
than those in detached and semi-detached systems. We calculate the binary
flares activity level (AL) of all the flare binaries, and discuss its
variations along the orbital period (P\_orb) and rotation period (P\_rot,
calculated for only detached binaries). We find that AL increases with
decreasing P\_orb or P\_rot up to the critical values at P\_orb near 3 days or
P\_rot near 1.5 days, thereafter, the AL starts decreasing no matter how fast
the stars rotate. We examine the flaring rate as a function of orbital phase in
2 eclipsing binaries on which a large number of flares are detected. It appears
that there is no correlation between flaring rate and orbital phase in these 2
binaries. In contrast, when we examine the function with 203 flares on 20
non-eclipse ellipsoidal binaries, bimodal distribution of amplitude weighted
flare numbers shows up at orbital phase 0.25 and 0.75. Such variation could be
larger than what is expected from the cross-section modification.