Nowak, G., Niedzielski, A., Wolszczan, A., Zieliński, P., Adamów, M., Gettel, S.
Red giants represent late phases of evolution of the main sequence stars. The planet induced Doppler shifts are easy to detect in radial velocity measurements of these stars, because they have cooler effective temperatures and lower rotational velocities compared to their main sequence progenitors. This offers a way to search for planets around stars that are significantly more massive than the Sun. However, when searching for planets around red giant stars with the radial velocity technique one has to take into account the effects of their atmospheric activity, pulsation, and spots that can mimic planetary signatures in radial velocity measurements. In this work, we discuss methods employed in the Pennsylvania-Toruń Planet Search (PTPS) to discriminate between the effects on radial velocity measurements caused by the Keplerian dynamics and those produced by the stellar atmospheric phenomena. In particular, we present the analysis of an atmospheric activity in several stars with possible planetary companions detected by the PTPS.
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