Blazhko-type fundamental-mode RR Lyrae stars in the globular cluster M3

Jurcsik, Johanna (2019) Blazhko-type fundamental-mode RR Lyrae stars in the globular cluster M3. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 490 (1). pp. 80-95. ISSN 0035-8711

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Abstract

Blazhko stars from the extended BVIC time series of RRab stars in the globular cluster M3 are analysed. This is the larges sample of Blazhko stars with full details of their Blazhko properties i a homogeneous stellar system. Blazhko periods and light-curve solution are determined/estimated for 83 fundamental-mode variables. The lack o phase modulation in Oosterhoff type II stars and the diminishin relative strength of the modulation in long-period Oosterhoff type stars are regular tendencies found between the pulsation and modulatio properties of Blazko stars. Similarly to previous results, no modulatio of the longest-period stars is detected. The onset of modulation in previously regular RRab star and the similar distribution of modulate and non-modulated stars imply that the modulation is a temporal propert of RR Lyrae (RRL) stars, which may occur at any time in any RRab sta except the coolest ones. Comparing the modulation periods in M3 and i other samples of Blazhko stars, the mean log(Pmod) value i found to depend on the metallicity of the system. The separation o temperature- and radius-change induced variations supports our previou finding that the photometric radius variation does not show an modulation. The pulsation-averaged mean brightness and temperature o Blazhko stars are found to be larger in the large-amplitude phase of th modulation than in the small-amplitude phase. The larger the amplitud of the modulation, the larger the changes of the mean parameter detected.

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