METHANOL AND HYDROXYL MASER POSITIONS

The Australia Telescope Compact Array has been used to study more than 40 sites of 1.665-GHz hydroxyl masers and 36 sites of 6.668-GHz metha nol masers. Maser positions accurate to better than 1 arcsec have been derived. At each maser site both species are commonly present, and co mparisons have been made between the methanol and OH. In 28 of the 29 cases where we have accurate measurements of both species, the methano l and OH coincide to within the errors, with nominal separations of le ss than 1.4 arcsec. In only one case do the two species apparently ari se from different sites, the separation in this instance exceeding 3 a rcsec. 1.665-GHz OH masers are known to be excellent indicators of the sites of ultracompact H II regions which envelop recently formed mass ive stars; our results confirm with high accuracy that masers of 1.665 -GHz OH and 6.6-GHz methanol generally pinpoint identical H II regions . Thus the same evolutionary phase of the H II region is conducive to both OH and methanol maser emission. We briefly discuss the precise di stribution of the masing molecules relative to the embedded star and i ts H II region, but this requires further study.