FIRST QUINTUPLET FREQUENCY SOLUTION OF A BLAZHKO VARIABLE: LIGHT CURVE ANALYSIS OF RV UMa

Abstract

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 Kany?, and the data were analysed by Kov?cs. After detecting an error in the reduction procedure of the published Konkoly data, corrected photometric data are presented with additional, previously unpublished measurements. The re-analysis of the combination of the corrected Konkoly data supplemented by Preston & Spinrad's observations has led to the discovery that the appropriate mathematical model of the light curve is, in fact, a quintuplet frequency solution, rather than, a triplet. This finding has crucial importance in the interpretation of the Blazhko phenomenon, as a triplet (doublet) is the preferred structure in resonance models, quintuplet in magnetic models. Period changes of both the pulsation and modulation light variations of RV UMa have been detected based on its century-long photometric observations. An overall anticorrelation between the pulsation and modulation period changes can be defined by dPBl /dP 0 = ?8.6 ? 104 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 the fact that there is no strict relation between the changes in the periods of the pulsation and modulation.