Khaled Al Moulla (University of Geneva): Roadblocks to Detect Earth-like Exoplanets: Solar-type Activity in Radial Velocities

Thursday 21 Mar 2024, 14:00 → 15:00 Europe/Stockholm

80101

Title: Roadblocks to Detect Earth-like Exoplanets: Solar-type Activity in Radial Velocities
Speaker: Khaled Al Moulla
Affiliation: University of Geneva
Time: Thursday 21st March 2024, 1400 to 1500
Location: 80101 Å

Abstract: 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.