First Hubble Space Telescope Observations of Mira AB Wind-accreting Binary Systems

The Mira AB system belongs to a class of detached binaries in which a compact object accretes mass from the wind of a cool giant or supergiant. This system provides a unique laboratory for detailed study of the characteristics of the wind accretion processes because it can be spatially resolved with the Hubble Space Telescope (HST) and the components can be studied individually at UV and optical wavelengths.

We resolved the components of this binary using HST Faint Object Camera (FOC) images and obtained spectra of each component separately for the first time. The multiwavelength FOC images combined with the spectra provide a unique perspective on this accreting system and its components at wavelengths ranging from 150 to 550 nm. We determined the spectral energy distribution of each component unambiguously at UV and optical wavelengths and obtained the first high spatial resolution images of Mira A and Mira B at UV wavelengths. We detected significant asymmetries in the giant's atmosphere and found evidence for possible interaction with its companion.