The Blazhko behaviour of RR Geminorum II -- long-term photometric results

TL;DR

This study analyzes 70 years of photometric data of RR Gem to understand its long-term pulsation and Blazhko modulation behavior, revealing significant amplitude variations, period correlations, and brightness changes.

Contribution

It provides the first detailed long-term analysis of RR Gem's pulsation and modulation properties, highlighting their correlated variations over decades.

Findings

Modulation amplitude varies from undetectable to 0.20 mag.

Parallel changes in pulsation and modulation periods with a ratio of about 1600.

Detected brightness and amplitude changes over 70 years.

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 d P_mod / d P_puls = 1.6 +/- 0.8 * 10^3 ratio. We also detected 0.05-0.1 mag changes in the mean maximum brightness and mean pulsation amplitude.