Radial-velocity Precision of ESPRESSO Through the Analysis of the Solar Twin HIP 11915

Abstract Different stellar phenomena affect radial velocities (RVs), causing variations large enough to make it difficult identify planet signals from the variability. RV caused by oscillations and granulation can be reduced through some methods, but impact of rotationally modulated magnetic activity on RV, due active regions, is harder correct. New instrumentation promises an improvement in precision one order magnitude, about 1 m s −1 10 cm . In this context, we report our first results 24 spectroscopic Echelle SPectrograph for Rocky Exoplanets Stable Spectroscopic Observations (ESPRESSO)/Very-Large Telescope observations solar twin star HIP 11915, spread over 60 nights. We used a Gaussian Process approach found 11915 residual rms scatter 20 , representing upper limit performance ESPRESSO.