Contemporaneous photometric and spectroscopic stellar granulation signals seen by CHEOPS and ESPRESSO

Stellar granulation generates fluctuations in both photometric and spectroscopic data with properties that depend on the type of the star, its composition, and its evolutionary state. Characterizing precisely these properties is key for the understanding of stellar atmospheres, but also for exoplanet detection where this stellar signal acts as a significant noise source.

In this talk, we present the first analysis of spectroscopic and photometric signatures of stellar granulation for a G0V and an F7V bright star with high precision observations taken contemporaneously with CHEOPS and ESPRESSO.
We first describe how we characterize this stellar signal from both datasets. We infer its statistical properties and compare them with the Sun, main-sequence stars observed by Kepler, and hydrodynamical simulations. We find consistent properties, which highlight the capability of both instruments to study this low amplitude stellar signal on short duration observations. These datasets also allow us to invalidate several relations that were empirically derived from past low precision surveys linking the photometric and spectroscopic observables while validating others.

In the context of the upcoming PLATO mission and its dedicated RV follow-up, we then conclude by presenting the impact of this stellar signal on both detection and characterization of long orbital period exoplanets and some new avenues to mitigate it.