|Spectroscopic Microvariability Induced by Convective Motions
|448, 16th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun
|Porter, L.; Asplund, M.
|Convection reaches the atmospheres of cool stars creating detectable variability in the photometry and
spectrum of the star. Current 3D hydro-dynamical models of dwarfs and red giants simulate only a small representative volume of the
stellar atmosphere, typically covering some 10 granules horizontally. To derive observable quantities it is necessary to
integrate these ‘Box-in-a-star’ models over the stellar disk. The disk-integrated variability caused by convective
motions can be constrained using the statistical properties of spatial and temporal fluctuations from a time-series
of these models. Previously suggested for white light and photometric centroid (Ludwig 2006), we extend this method to spectral
lines, including the effects of stellar rotation. We believe a better characterisation of this convective microvariability
would benefit velocity diagnostics for helioseismology, eg NiI 6768 Å, used by SOHO MDI (Jones 1989)
and could be used to remove the ‘noise’ induced by convective motions in radial velocity planet searches.