A search for SiO masers in Orion-like regions

A sensitive search for SiO maser emission toward objects possessing high-velocity flows and/or disk geometries has revealed no Orion-like sources. The ratios of the luminosity limits reported here to the Orion SiO maser luminosity range from 0.04 to 0.0002, indicating that the Orion masers are associated with a unique set of physical conditions and not any widespread phenomena, even at a weak level. The authors report detection of a new SiO maser toward the reflection nebula OH231.8+4.2, exhibiting characteristics typical of the SiO masers seen toward late-type stars.