Granulation in Red Supergiants: The Scaling Relations

Abstract

AbstractThe evolution of granulation is an important mechanism of the light variations of red supergiants (RSGs). Based on pure and complete samples of RSGs in the Magellanic Clouds, the mechanisms and characteristics of the granulation of RSGs are investigated based on time-series data. As predicted by the basic physical process of granulation and previous works, there are tight relations between granulation and stellar parameters of RSGs (i.e., the scaling relations). The scaling relations of RSGs provide a new method to infer stellar parameters by using the characteristic timescale and amplitude of granulations. Some faint sources deviate from the scaling relations, which may be due to the difference in the properties of the granulation of the RSGs before and after the blue loop or contamination by Mira variables. However, both of these possibilities suggest that the scaling relations of granulation is different among different types of stars.