Investigating the properties of granulation in the red giants observed by Kepler

TL;DR

This study analyzes the granulation properties of over 1000 red giants observed by Kepler, revealing correlations with stellar parameters and comparing results with 3D convection models.

Contribution

It provides a comprehensive analysis of granulation in red giants using Kepler data and compares observational results with theoretical 3D models.

Findings

Anti-correlation between granulation timescale/amplitude and acoustic mode power

Correlation of granulation parameters with stellar radius

Agreement of results with convection theory and models

Abstract

More than 1000 red giants have been observed by NASA/Kepler mission during a nearly continuous period of ~ 13 months. The resulting high-frequency resolution (< 0.03 muHz) allows us to study the granulation parameters of these stars. The granulation pattern results from the convection motions leading to upward flows of hot plasma and downward flows of cooler plasma. We fitted Harvey-like functions to the power spectra, to retrieve the timescale and amplitude of granulation. We show that there is an anti-correlation between both of these parameters and the position of maximum power of acoustic modes, while we also find a correlation with the radius, which agrees with the theory. We finally compare our results with 3D models of the convection.