First quintuplet frequency solution of a Blazhko variable: light curve analysis of RV UMa

RV UMa is one of the RRab stars showing regular large amplitude light curve modulation. Extended photoelectric observations of RV UMa obtained at the Konkoly Observatory were published by Kanyo (1976). The analysis of the data was published by Kovacs (1995). After detecting an error in the reduction procedure of the published Konkoly data, corrected photometric data are presented with additional, previously unpublished measurements. The reanalysis of the combination of the corrected Konkoly data supplemented with Preston & Spinrad's (1967) observations has led to the discovery that the adequate mathematical model of the light curve is, in fact, a quintuplet, instead of a triplet frequency solution. This finding has crucial importance in the interpretation of the Blazhko phenomenon, as triplet (doublet) is the preferred structure in the resonance models, quintuplet in the magnetic models. Period changes of both the pulsation and the modulation light variations of RV UMa have been detected based on its century long photometric observations. An overall anticorrelation between the pulsation and the modulation period changes can be defined with dP_{Bl} / dP_0 = -8.6 pm 10^4 gradient, i.e., the modulation period is longer if the pulsation period is shorter. Between 1946 and 1975 the pulsation and modulation periods showed, however, parallel changes, which points to that there is no strict relation between the changes in the periods of the pulsation and the modulation.