A SEARCH FOR SIO MASER EMISSION FROM SYMBIOTIC MIRAS

A sample of 29 dusty symbiotics, mostly containing Mira primaries, has been observed in the 86GHz, v=1, J=2-1 transition of SiO, to look for maser emission. Apart from R Aqr, a known maser source, no objects we re detected. By comparing our results with those previously obtained o n normal Miras and LPVs, we find that in symbiotics the masers are gen erally underluminous, or absent. By considering the possible influence of the UV radiation and tidal effects of the compact companion on the maser sites, we conclude that the likely reason for the lack of SiO m aser emission from symbiotics whose orbits are not too wide is tidal d isruption of the stationary or deeper layers in the Mira atmosphere. F or probable wide orbit systems like RX Pup the mechanism inhibiting th e SiO maser emission is still unknown. We present and discuss a time s eries of maser spectra of R Aqr.