CHARA/MIRC interferometry of red supergiants: diameters, effective temperatures and surface features

TL;DR

This study uses H-band interferometry to measure red supergiants' diameters, temperatures, and surface features, revealing hotspots and supporting a hotter temperature scale, with implications for mass-loss processes.

Contribution

First detection of surface hotspots in H-band on red supergiants, linking surface features to mass-loss and confirming a revised hotter temperature scale.

Findings

Detection of hotspots on all observed stars.

Support for the hotter temperature scale of RSGs.

Possible correlation between surface spots and circumstellar dust emission.

Abstract

We have obtained H-band interferometric observations of three galactic red supergiant stars using the MIRC instrument on the CHARA array. The targets include AZ Cyg, a field RSG and two members of the Per OB1 association, RS Per and T Per. We find evidence of departures from circular symmetry in all cases, which can be modelled with the presence of hotspots. This is the first detection of these features in the $H$-band. The measured mean diameters and the spectral energy distributions were combined to determine effective temperatures. The results give further support to the recently derived hotter temperature scale of red supergiant stars by Levesque et al. (2005), which has been evoked to reconcile the empirically determined physical parameters and stellar evolutionary theories. We see a possible correlation between spottedness and mid-IR emission of the circumstellar dust, suggesting a connection between mass-loss and the mechanism that generates the spots.