Roadblocks to Detect Earth-like Exoplanets: Solar-type Activity in Radial Velocities

by Mr Khaled Al Moulla (University of Geneva)

Friday 22 Mar 2024, 10:30 → 11:30 Europe/Stockholm

FC61 (AlbaNova Main Building)

The radial velocity (RV) technique for detecting exoplanets has in recent years been limited in its applicability to search for Earth-mass planets due to their small semi-amplitudes relative to the intrinsic variability of their host stars. In this talk, I will present the signatures of stellar activity in high-resolution optical and near-infrared (NIR) spectral time series of the Sun and solar-type stars, observed with the HARPS, HARPS-N and NIRPS spectrographs. I will talk about a novel, physically motivated method of RV extraction based on the average formation temperature of spectral segments, in order to demonstrate the differential effect of stellar activity signals as a function of photospheric depth, enabling the separation of temperature-dependent stellar activity from constant Keplerian signals. Additionally, I compare the chromaticity of unsigned magnetic field proxies in the optical versus NIR to evaluate their usefulness as activity indicators with which the stellar signals can be mitigated.

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