The Blazhko behaviour of RR Geminorum II ^*

Long-term photometric results

Konkoly Observatory of the Hungarian Academy of Sciences, PO Box 67, 1525 Budapest, Hungary e-mail: sodor,szeidl,jurcsik@konkoly.hu

Received: 6 December 2006
Accepted: 30 March 2007

Abstract

Context.RR Gem is one of the few Blazhko RR Lyrae that has photometric observations available extended enough to study the long-term courses of its pulsation and modulation properties in detail.

Aims.We investigate the pulsation and modulation properties and the relations between them in RR Gem using photometric observations from the past 70 years in order to gain further insight into the nature of the Blazhko modulation.

Methods.We studied the photographic, photoelectric, and CCD light curves obtained at the Konkoly Observatory and other authors' published maxima observations. Detailed analysis of the light curves, maximum brightness, and O–C data are carried out.

Results.RR Gem showed modulation most of the time it was observed. The modulation amplitude showed strong variations from the undetectable level (less than 0.04 mag in maximum brightness) to about 0.20 mag. The amplitudes of the amplitude and phase modulations showed parallel changes, thus the total “power” of the modulation have changed during the past 70 years. Parallel changes in the pulsation and modulation periods occur with a = 1.6 ± 0.8 10³ ratio. We also detected mag changes in the mean maximum brightness and mean pulsation amplitude.