Period Changes of the Algol-type Eclipsing Binary LS Persei (Abstract)

Volume 35 number 1 (2007)

Gary Billings

Abstract

(Abstract only) Archival observations using the Harvard College Observatory Photographic Plate Collection have provided 251 magnitude estimates, yielding eighteen timings of minima for LS Persei back to 1889. Data from 1889–1935 (I series plates) and 1931–1950 (RH series plates) show different periods, which are different again from the GCVS (1960s and 1970s) and later periods. In addition, two CCD times of minima were obtained in late 2005 that confirm a period increase, suggested by 1990s visual timings, of about 0.003% since 1990. Overall, the period of LS Per has decreased by 0.025% between 1889 and 2005. The O–C data can be fit by assuming intervals of constant period separated by abrupt period changes. Alternatively, if continuous period decrease is assumed, the residuals show cyclic variations of alternating sign. Possible mechanisms for this will be discussed.