CHARA/MIRC observations of two M supergiants in Perseus OB1: temperature, Bayesian modeling, and compressed sensing imaging

TL;DR

This study uses advanced interferometric and statistical techniques to analyze red supergiants RS Per and T Per, revealing surface asymmetries, spots, and temperature estimates that support hotter temperature scales.

Contribution

Developed new Bayesian and compressed sensing methods for analyzing asymmetric stellar surfaces in interferometric data.

Findings

Detected near-infrared spots covering 3-5% of stellar flux.

Confirmed departure from circular symmetry in stellar surfaces.

Supported hotter temperature scales for red supergiants.

Abstract

Two red supergiants of the Per OB1 association, RS Per and T Per, have been observed in H band using the MIRC instrument at the CHARA array. The data show clear evidence of departure from circular symmetry. We present here new techniques specially developed to analyze such cases, based on state-of-the-art statistical frameworks. The stellar surfaces are first modeled as limb-darkened discs based on SATLAS models that fit both MIRC interferometric data and publicly available spectrophotometric data. Bayesian model selection is then used to determine the most probable number of spots. The effective surface temperatures are also determined and give further support to the recently derived hotter temperature scales of red su- pergiants. The stellar surfaces are reconstructed by our model-independent imaging code SQUEEZE, making use of its novel regularizer based on Compressed Sensing theory. We find excellent agreement between the model-selection results and the reconstructions. Our results provide evidence for the presence of near-infrared spots representing about 3-5% of the stellar flux.