Name/Affiliation: Raphaelle D. Haywood (University of St Andrews)
Understanding the Sunís activity to improve exoplanet radial-velocity detections
The detection and characterisation of low-mass exoplanets through radial-velocity (RV) surveys is predominantly limited by the intrinsic variability of the stars themselves. In order to understand and model the effects of stellar activity on RV observations, we use the Sun as a test case for study. Using HARPS spectra of sunlight reflected off the bright asteroid Vesta, we have obtained the Sunís activity-driven RV variations over two solar rotations. Combining these results with high spatial resolution images from SDO/HMI allows us to deduce the RV signature of individual photospheric structures such as spots, faculae/plage, and surface granulation. We model the activity-induced RV variations of the Sun in terms of the continuum lightcurve, the chromospheric Ca II H&K emission and the line-profile distortions produced by spots drifting across the solar disk. The aim of this work is to identify photometric and spectroscopic proxies that will be key to disentangling planetary orbits from stellar activity.