17th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun

Type: Poster

Topic: Cool Stars as Exoplanet Hosts

Abstract
Space-based, photometric transit surveys have moved us into a new era of exoplanet discovery, identifying thousands of planetary candidates. However, radial velocity (RV) follow-up is mandatory for most systems to measure the candidate’s mass and thereby confirm its planetary nature. To do this for low-mass planets typically requires cm s$^{-1}$ RV precision. Unfortunately, astrophysical noise sources (or stellar jitter) due to spots, plages, granulation and stellar oscillations, for example, become an issue at the m s$^{-1}$ level. These phenomena alter the shape of the stellar absorption lines, injecting spurious or systematic RV signals that may mask or mimic planetary signals. As such, active stars are not ideal candidates for RV follow-up and are thus often left out of planet surveys. Unfortunately, even `quiet' stars (those with little or no activity) exhibit jitter due to granulation and stellar oscillations. For this small-scale jitter, the currently implemented removal technique rests on adapting observational strategies to average out such noise. However, this technique is observationally intensive and does not provide information on the nature of jitter. We present our techniques to explore stellar jitter due to granulation through the use of sophisticated 3D magnetohydrodynamical simulations of the Sun. In addition, we also present the identification of an entirely new source of stellar jitter that has been hitherto unrecognised and that could impact the RV follow up and confirmation of low-mass terrestrial planets and Earth-like worlds.