Scaling relations of convective granulation noise across the HR diagram from 3D stellar atmosphere models

Abstract

Thanks to high precision photometric data from space missions, our understading of stellar granulation has vastly improved, since these observations have shown in great detail the stochastic brightness fluctuations of stars across the HR diagram. These fluctuations need to be quantified to detect and characterize exoplanets accurately. In this poster, I will present new scaling relations between granulation properties, such as the brightness fluctuation and characteristic timescale, with stellar parameters such as the peak frequency \(\nu_{max}\). This was achieved by using long time series of 3D stellar atmosphere models at different metallicities and across the HR diagram, generated with the STAGGER-code. To validate our results, we compared our theoretical granulation properties with the values of a large sample of <em>Kepler</em> stars from the literature, and analyzed selected stars with accurate stellar parameters as well. I will also show that, unlike previous studies, the brightness fluctuations of our 3D models reproduce very well the granulation noise from <em>Kepler</em> targets. Regarding the timescales, I will show that the 3D models reproduce the values obtained with the sample of <em>Kepler</em> stars with accurate stellar parameters, but did not fully reproduce the timescales provided for the larger sample in the literature, which might be due to the use of scaling relations in the determination of stellar parameters. Finally, I will also illustrate the role of metallicity in the granulation properties of our 3D models.