Searching for Rotational and Activity Signals in M Dwarf Stars

Abstract

We search for signals coming from M dwarf stars through variations caused by stellar surface activity. The aims of this work are to find the stellar rotation period of M dwarf stars and check them against known planetary signals. We used photometric ASAS data for 36 M dwarf stars with literature rotation periods. We used our own noise filtering code and the Systemic Console program to identify the significant signals. In addition, we investigate the correlation between the M dwarf rotation and chromospheric emission, represented by H and CaII H&K lines. This research has provided valuable information regarding how to identify correct stellar rotation periods. We show a good agreement between our photometric rotation periods and corresponding photometric periods in the literature. On the other hand we only find agreement for 8 out of 20 targets where a spectroscopic rotation periods is in the literature. We confirm that several planetary signals of candidate planets reported in the literature are very different to the stellar rotation periods of host stars. For early M dwarfs with periods of less than 40 days we find a relationship between the level of activity as measured by H and CaII H&K lines and the photometric rotation period.