Monitoring the Dust Emission from R Aqr with SOFIA: Eclipse and Periastron Passage

Abstract We present infrared (IR) spectra from our monitoring of the symbiotic Mira, R Aquarii, using the Stratospheric Observatory for Infrared Astronomy. New mid-IR photometric and spectroscopic observations using the FORCAST instrument were obtained in 2022 September, when the system was well into the eclipse phase. The 10 μ m silicate feature has increased in strength since the previous observations, obtained in 2019 October. Radiative transfer models of the emission show that the dust density has increased by a factor of about 2 in this period. Three epochs of far-IR photometric observations obtained with the HAWC+ instrument between 2018 July and 2020 September are also presented here. The emission at the sampled wavelength bands ranging from 53 to 214 μ m does not vary significantly, in contrast to the mid-IR silicate dust emission that shows large variations. The models suggest that the far-IR emission arises much further out in the circumstellar dust shell and is not affected by the dynamics in the inner regions that impact the mid-IR emission.