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

Abstract

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

arXiv comment20 pages, 4 figures, accepted for publication in the Astrophysical Journal

References in corpus (15)

• Color Transformations for the 2MASS Second Incremental Data Release
• A catalogue of symbiotic stars
• Early Science with SOFIA, the Stratospheric Observatory for Infrared Astronomy
• Dust formation in the oxygen-rich AGB star IK Tau
• Classification of 2.4-45.2 Micron Spectra from the ISO Short Wavelength Spectrometer
• The spectroscopic orbit and the geometry of R Aqr
• Large-scale environments of binary AGB stars probed by Herschel - I. Morphology statistics and case studies of R Aquarii and W Aquilae
• Accurate Parallax Measurement toward the Symbiotic Star R Aquarii
• Near-infrared spectro-interferometry of Mira variables and comparisons to 1D dynamic model atmospheres and 3D convection simulations
• Phase Lags in the Optical-Infrared Light Curves of AGB Stars
• High-resolution observations of the symbiotic system R Aqr. Direct imaging of the gravitational effects of the secondary on the stellar wind
• The bipolar jet of the symbiotic star R Aquarii: A study of its morphology using the high-resolution HST WFC3/UVIS camera
• New insights into the outflows from R Aquarii
• CO envelope of the symbiotic star R Aqr seen by ALMA
• CO observations of symbiotic stellar systems