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Towards understanding stellar variability at the sub m/s level: granulation-induced variability across the optical spectrum

arxiv.org · 8,701 words · saved by 1 readers

Detecting the radial velocity signal of Earth-mass exoplanets requires the characterisation and removal of granulation-induced radial velocity variability from spectroscopic observations. By coupling state-of-the-art three-dimensional (3D) hydrodynamic (HD) simulations to a radiative transfer code, we can isolate and study the effect of granulation on stellar lines. In this study we isolated the impact of granulation on spectral line shapes and shifts for the largest and most diverse synthetic spectral line sample to date. Our aims were twofold. First, we quantified how granulation affects the temporal evolution of shapes and shifts of 72 unblended spectral lines in two wavelength regions: 5500 − 5600 Å and 6100 − 6200 Å, from disc centre to the stellar limb. Second, we investigated if spectral lines behave coherently in their line shape variability and, if so, can lines be grouped together that behave similarly. We find that weak lines show the largest radial-velocity variability

2026Towards understanding stellar variability at the sub m/s level: granulation-induced variability across the optical spectrum–19 Cis Lagae, Ginger Frame, Heather M. Cegla, Veronika Witzke, René Holzreuter, Sergiy Shelyag, Christopher Watson, Alexander Shapiro, ††thanks: E-mail: cis.lagae@warwick.ac.uk Affiliation: Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK Affiliation: Centre for Exoplanets and Habitability, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK Affiliation: University of Graz, Institute of Physics, Universitätsplatz 5,…

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