Mid-infrared variations of R Coronae Borealis stars

Abstract

Mid-infrared (IR) photometry of R Coronae Borealis stars obtained from various satellites from Infrared Astronomical Satellite (IRAS) to Wide-field Infrared Survey Explorer (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 (Td) 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 ∝ T 4 d developed in the paper is satisfied, especially by those stars for which a single collection of clouds dominates the IR fluxes.