First Antarctica light curve - PAIX monitoring of the Blazhko RR?Lyrae star: S?Arae

摘要

Context. In the context of long and continuous time-seriesphotometry and after the MOST, CoRoT, KEPLER space missions and largegeographic longitude ground-based networks, a new method is offered bythe polar location helping to cope with the problem associated with theEarth's day-night cycle. Aims. We present the first long time -series photometry from Dome Charlie in the heart of Antarctica and analyze 4400 photometric measurements of RRLyrae star SArae obtained in July and August 2007. Methods. The 40-cm telescope and Photometer AntarctIcaeXtinction named PAIX were used for long photometric measurements withhigh time resolution and a duty cycle of 65%. The Fourier technique wasused for the frequency analysis. New high-precision spectroscopicobservations of SArae were also collected using HARPS over onepulsation cycle of SArae. Results. We confirm the known radial fundamental period of0.452day. The high order of its harmonics shows the nonlinearnature of the radial mode. The Blazhko modulation is directly detectedin the spectrum and shows a value around 48d. Together with theBlazhko frequency we also detected triplet structure components up to15th order showing a nonlinear behavior of the Blazhko modulation.Thus, we conclude that SArae is a bona fide Blazhko star. Thedata reveal that there are irregular changes in the SAraeatmosphere during the Blazhko cycle. A residual scatter phenomenon isdetected and is more intense where the nonlinear effects are strongest.Therefore, the connection between temporal hydrodynamic phenomena andsuch modulation has to be taken into account in Blazhko models. Conclusions. High-precision CCD photometry with a very good timeresolution can be undertaken at Dome Charlie in Antarctica, and ithelps to complete astrophysical measurement time-series. Key words: techniques: spectroscopic - methods: data analysis -techniques: photometric - shock waves - stars: variables: RR Lyrae -stars: atmospheres