Mid-Infrared Variations of R Coronae Borealis Stars

TL;DR

This study analyzes three decades of mid-infrared data from satellites like IRAS and WISE to understand dust cloud evolution around R Coronae Borealis stars, revealing a key temperature-coverage relation and correlations with stellar properties.

Contribution

It introduces a predictive relation R ∝ T_d^4 for dust cloud coverage and temperature, enhancing understanding of dust evolution in R Coronae Borealis stars.

Findings

The R ∝ T_d^4 relation is confirmed for stars with dominant dust clouds.

Correlations between dust coverage and stellar luminosity are identified.

Variations in dust temperature and coverage over decades are characterized.

Abstract

Mid-infrared photometry of R Coronae Borealis stars obtained from various satellites from IRAS to WISE has been utilized in studying the variations of the circumstellar dust's contributions to the spectral energy distribution of these stars. The variation of the fractional coverage (R) of dust clouds and their blackbody temperatures (T$_d$) have been used in trying to understand the dust cloud evolution over the three decades spanned by the satellite observations. In particular, it is shown that a prediction R $ \propto T_d^4$ developed in this paper is satisfied, especially by those stars for which a single collection of cloud dominates the IR fluxes. Correlations of R with photospheric abundance and luminosity of the stars are explored.