SOFIA/FORCAST Monitoring of the Dust Emission from R Aqr: Start of the Eclipse

Abstract We present mid-infrared (mid-IR) spectra from our continued monitoring of R Aquarii, the nearest symbiotic Mira, using Stratospheric Observatory for Infrared Astronomy (SOFIA). New photometric and spectroscipic data were obtained with Faint Object infraRed CAmera SOFIA Telescope in 2018 2019 after system had started its “eclipse,” during which it became two magnitudes fainter visual. The mid-IR flux, particular 10 μ m silicate feature, has strengthened compared previous cycles. Radiative transfer models circumstellar dust emission calculated new spectra, recalculated those previously more appropriate values near-IR to constrain properties asymptotic giant branch heating dust. modeling shows that luminosity dependence on pulsation phase is not affected by onset eclipse, increase flux due a higher density. also confirm earlier results micron-size grains are present, no changes grain composition required explain variations spectra.