What is the Difference? Blazhko and Non-Blazhko RRab Stars and the Special Case of V123 in M3

Jurcsik, Johanna and Smitola, Péter József and Hajdu, Gergely and Pilachowski, C. and Kolenberg, K. and Sódor, Ádám and Fűrész, Gábor and Moór, Attila and Kun, Emma and Saha, A. and Prakash, P. and Blum, P. and Tóth, Imre (2013) What is the Difference? Blazhko and Non-Blazhko RRab Stars and the Special Case of V123 in M3. ASTROPHYSICAL JOURNAL LETTERS, 778 (2). ISSN 2041-8205

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Abstract

In an extended photometric campaign of RR Lyrae variables of the globular cluster M3, an aberrant-light-curve, non-Blazhko RRab star, V123, was detected. Based on its brightness, colors and radial velocity curve, V123 is a bona fide member of M3. The light curve of V123 exhibits neither a bump preceding light minimum, nor a hump on the rising branch, and has a longer than normal rise time, with a convex shape. Similar shape characterizes the mean light curves of some large-modulation-amplitude Blazhko stars, but none of the regular RRab variables with similar pulsation periods. This peculiar object thus mimics Blazhko variables without showing any evidence of periodic amplitude and/or phase modulation. We cannot find any fully convincing answer to the peculiar behavior of V123, however, the phenomenon raises again the possibility that rotation and aspect angle might play a role in the explanation of the Blazhko phenomenon, and some source of inhomogeneity acts (magnetic field, chemical inhomogeneity) that deforms the radial pulsation of Blazhko stars during the modulation.

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