On a Long-term Variability of the Asynchronous Polar BY Cam

A long-term monitoring of the asynchronous polar BY Cam has been carried out by several groups of observers in a total over the years 1988-2012. Apart from the 3.3-hr periodicity related to the orbital variation and similar to 15 d periodicity caused by the the spin-orbital asynchronizm, BY Cam displays the brightness variation on the much longer time scale of hundreds and thousands of days. Basing on our 8-year interval of photometric observations from 2004 to 2012, we examined the existence of 100-150 d precession of the white dwarf spin axes suggested by Piirola et al. (1994) and similar to 5 year quasi-period found by Honeycutt and Kafka (2005) in brightness variations. We did not find any convincing evidence of the similar to 145 d period observed by Honeycutt and Kafka (2005). Instead we found the existence of similar to the 4.1-year variations in the years 2004-2012 and present their sine-like profile. The possible connection of these variations with similar to 5 year quasi-period as well as its interpretation is considered.