2013MNRAS.434..552C

We present a first detailed atmospheric dynamics study of 11 RRab stars: six Blazhko stars - RR Lyr, AS Vir, BS Aps, CD Vel, UV Oct and V1645 Sgr, and five non-Blazhko stars - DT Hya, WY Ant, XZ Aps, Z Mic and RV Oct. 32 hundred high-resolution spectra of these RRab stars were collected, during their pulsation periods and the Blazhko cycles, with the du Pont 2.5-m telescope at the Las Campanas Observatory and the 1.5-m telescope at the Haute Provence Observatory. We derived the dynamical parameters: dynamical accelerations, radius variations, rise time, shock amplitudes, full width at half-maximum (FWHM) and their variation during the Blazhko modulation. We find that, rise time excepted, these dynamical parameters are anticorrelated with change in instantaneous pulsation period during the Blazhko cycle. We detected a new bulge phenomenon in the radial velocity curve of Blazhko and non-Blazhko stars of our sample and we discuss newly detected redshifted Hα emission and its evolution during declining light. A new bump in the light curve is also detected: the lump. We associate the bulge phenomenon, lump and the redshifted emission with a new post-maximum shock wave ShPM. The bulge phenomenon and lump vary from star to star and with phase during Blazhko cycles of individual stars. We suspect but cannot prove irregularity from cycle to cycle in the radial velocity and FWHM curves of non-Blazhko stars. Finally, we discuss the origin of the Blazhko effect, giving a new empirical side for further theoretical models.