Title: Measuring precise radial velocities and cross-correlation function line-profile variations using a skew normal density
Authors: Umberto Simola - University of Helsinki (Finland) [presenting]
Jessi Cisewski - Yale University (United States)
Xavier Dumusque - Branco Weiss Fellow--Society in Science (Switzerland)
Abstract: Stellar activity is one of the primary limitations to the detection of low-mass exoplanets using the radial velocity technique. Stellar activity can be probed by measuring time dependent variations in the shape of the cross-correlation function (CCF), often estimated using different parameters of the modelled CCF. A novel approach is to estimate the parameters of the CCF by fitting a skew normal density which, unlike the commonly employed normal density, includes a skewness parameter to capture the asymmetry of the CCF induced by stellar activity and also the natural asymmetry induced by convective blueshift. The performance of the proposed method is compared to the commonly employed normal density, using both simulations and real observations, with different levels of activity and signal-to-noise ratio levels. To use of the skew normal density results helpful to retrieve the different parameters of the CCF, since the correlations used to probe stellar activity are stronger than the ones retrieved by the common approach and because the uncertainties associated to the RV and the asymmetry of the CCF are both smaller than the ones retrieved by the commonly employed strategies.