Title: Towards understanding stellar variability at the sub m/s level
Speaker: Cis Lagae
Affiliation: University of Warwick
Time: Thursday 11 December 2025, 1400 to 1500
Location: Å80121
Abstract:
Since the detection of the first planet orbiting another star than the Sun, the number of known exoplanets has increased significantly. Still, one of the major challenges in exoplanet astronomy remains to find an analogue of our own earth. Space missions such as PLATO are expected to detect several earth-like exoplanets orbiting in the habitable zone of Sun-like stars. However, confirmation of these detections will require extremely precise radial-velocity measurements of the stellar system. For an earth-mass exoplanet orbiting a Solar-like star, the Doppler shift is of the order of ~10 cm/s.
Currently, radial velocity noise from the exoplanet hosting star, originating from stellar activity such as faculae and granulation, hampers the detection and characterization of earth-mass exoplanets. A profound understanding of how spectral lines behave in the presence of these stellar components is necessary to eliminate such radial velocity noise from observations. In this context, we have build a framework that isolates and characterizes the radial velocity signature due to granulation for individual, synthetic, spectral lines computed from 3D stellar models. Building on this, we expanded the method to larger spectral regions, including tens of spectral lines, with the goal of mimicking real disk-integrated stellar observations. Using this method, we have quantified how granulation affects the properties and radial velocities of spectral lines differentially, from disk centre to the stellar limb. This work will enable us to identify key granulation noise diagnostics across the optical spectrum that can be used to reduce the granulation-induces radial velocity noise from observations.