Poster Open Access

Detecting sub-stellar companions using the stellar pulsation timing method

Mackebrandt, Felix; Schuh, Sonja

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We investigate variations in the arrival time of coherent stellar pulsations due to the light travel time effect to test for the presence of sub-stellar companions. This timing method is particularly sensitive to planets at large distances and complementary to other exoplanet detection methods which are not efficient for systems with small transit probabilities or high intrinsic radial velocity noise and thus enhances the diversity of potential exoplanet host stars that can be probed with PLATO.

First, we apply this method to subdwarf B stars (sdB). Companions are the key to the possible formation scenario of apparently single sdB stars. During the RGB the star would develop a common envelope with a giant planet that leads to the loss of the envelope and leaves a helium burning sdB star.
We investigate the extensive set of ground based observations the four large amplitude p-mode pulsators DW Lyn, V1636 Ori, QQ Vir and V541 Hya from the EXOTIME project and can derive upper limits on sub-stellar companion masses from the observations.

Second, we probe pulsating evolved main-sequence A stars as exoplanet host stars. The mostly uninterrupted observations of space missions provide a large sample of such delta Scuti observations. Planet occurrence rates predict a maximum for host stars with masses close to the mass of delta Scuti stars. However, actual planet detections are affected by observational selection effects, effecting especially retired A stars. We confirm previously detected exoplanets orbiting delta Scuti stars, using Kepler data.

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