| We describe highly sensitive searches for 1612-MHz OH and 22 335-MHz H2O maser emission from symbiotic Mira variables, otherwise known as D(usty)-type symbiotic stars. Only two objects were detected, namely H1-36 and R Aqr, which are discussed in detail elsewhere. Here, we focus on a comparison between symbiotic and isolated Miras, and show that there is a statistically significant deficiency in maser emission in the symbiotics, provided that comparisons are made within the same range of IR colour. We propose a mechanism for the deficiency, in which a powerful wind from the hot companion sweeps much of the volume of the dusty Mira wind away from the hot companion, thus exposing the Mira to UV emission. The UV emission then photodissociates molecules responsible for all known masers. Dissociation even occurs on the side away from the hot companion as a consequence of Rayleigh scattering of UV photons by the inner region of the Mira wind. The absence of masers in symbiotics thus has the potential to contribute to the understanding of the symbiotic phenomenon in Mira variables. |
Comments:
Upper limit for non-detections: 0.075 Jy (3σ)
Detected sources H1-36 and R Aqr were not included. They are discussed in IVI94.
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