2007MNRAS.378..757P

We present 31 bright eclipsing contact and semidetached binaries that showed high period change rates (HPCRs) in a 5-yr interval in observations by the All-Sky Automated Survey. The time-scales of these changes range from only 50 up to 400 kyr. The orbital periods of 10 binaries are increasing and of 21 are decreasing, and even a larger excess is seen in contact binaries, where the numbers are 5 and 17, respectively. Period change has previously been noticed for only two of these binaries; our observations confirmed a secular period drift for SV Cen and period oscillations for VY Cet. The spectroscopic quadruple system V1084 Sco shows both period change and brightness modulation. According to our results, the incidence of asymmetry in the brightness at maximum light in the HPCR domain may be different from the incidence in the general population. All investigated binaries were selected from a sample of 1711 (1135 contact and 576 semidetached) that fulfilled all criteria of data quality. We also introduce a `branch' test to check if luminosity changes on part of the binary's photosphere have led to a spurious or poorly characterized period change detection.