PERIODIC BEHAVIOUR OF STARS IN THE GEOS RR LYRAE DATABASE PAPER 2: LONG-TERM STABILITY OF THE BLAZHKO PERIOD IN AR HER

摘要

The GEOS database of 0 — C values for RR Lyrae stars has been used to investigate 104 years' of data for the RRab-type variable star AR Her. The pulsation period of the star has changed at least three times during that time. The star is known to have a lazhko period of about 31.6 days, but it has been found to have changed from 31 544 ± 0.037 days to 31918 ± 0.058 days between the early and later data. There are other long-term vari ations in the 0 — C diagram which represent slow changes in the pulsation period of the star on a time scale of tens of years. The shape of the Blazhko 0 — C phase diagrams has remained the same over the whole 104 years despite the changes in the pulsation period of the star and the other long-term changes in the pulsation period.