Betelgeuse fainter in the sub-millimetre too: an analysis of JCMT and APEX monitoring during the recent optical minimum

TL;DR

This study reports a 20% dimming of Betelgeuse in sub-millimetre wavelengths during its recent optical minimum, suggesting changes in the star's photosphere rather than its dust environment.

Contribution

The paper provides a 13-year submillimetre monitoring of Betelgeuse, revealing correlated dimming and proposing a photospheric origin for the observed variability.

Findings

Betelgeuse dimmed by ~20% at sub-millimetre wavelengths during optical minimum.

Dimming likely caused by changes in the star's photosphere, not surrounding dust.

Radiative-transfer models support photospheric luminosity variations as the cause.

Abstract

Betelgeuse is the nearest Red Supergiant star and it underwent an unusually deep minimum at optical wavelengths during its most recent pulsation cycle. We present submillimetre observations taken by the James Clerk Maxwell Telescope and Atacama Pathfinder Experiment over a time span of 13 years including the optical dimming. We find that Betelgeuse has also dimmed by \sim20\% at these longer wavelengths during this optical minimum. Using radiative-transfer models, we show that this is likely due to changes in the photosphere (luminosity) of the star as opposed to the surrounding dust as was previously suggested in the literature.