PERIODIC BEHAVIOUR OF STARS IN THE GEOS RR LYRAE DATABASE PAPER 4: THE LONG-TERM BEHAVIOUR OF BLAZHKO'S STAR, RW DRA

摘要

The GEOS database on RR Lyr variable stars has been used to analyse 68o times of maximum obtained over IO4 years for the star RW Dra, Blazhko's star. Between approximately 1914 and 1938 the pulsation period of the star went through four large changes, including three occasions when the pulsation period changed by a significant fraction of one per cent over a few hundred cycles. These rapid period changes stopped in about 194o. From approximately 194o until 1959 the pulsation period was longer than average and slightly variable. This was followed by about twelve years when the pulsation period was shorter than average. Since approximately 1968 the period has probably been constant. The Blazhko period of the star has varied over the 104 years between values of approximately 41·3 days and 42 days.