The Pulsational Behavior of the High Amplitude delta Scuti Star RS Gruis

Volume 40 number 1 (2012)

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Jaime García

Instituto Copérnico, Gutiérrez 4500, 5603 Rama Caída, Mendoza, Argentina��; jgarcia@institutocopernico.org

Abstract

RS Gruis is a high–amplitude d Scuti–type variable star with a mean amplitude of almost half a magnitude in V and a period of almost 3.5 hours. The most recent study of this star by Derekas et al. (2009) suggests the presence of a low–mass dwarf star companion close to the variable star with a period of 11.5 days. Rodriguez et al. (1995) have also shown a decreasing rate of the period of dP/Pdt = –10.6 × 10–8 / y. Using an extended dataset comprising BVIc CCD observations acquired at the Astronomical Observatory of the Instituto Copérnico, data from ASAS and HIPPARCOS, and the existing CCD observations in the AAVSO International Database, we have performed an extensive periodgram and times of maximum analysis looking for long term variations. As a preliminary result, we confirmed that the period varies, but, since 1995, instead of decreasing, it has increased. We also found a small peak in the power spectrum in good agreement with the period suggested for the binary companion.