Radio and infrared observations of the OH maser source OH 351.78-0.54

Abstract

Observations of the region associated with the highly variable maser source OH 351.78--0.54 at several radio and infrared wavelengths are reported. Strong emission from water vapor and carbon monoxide was detected at nearly the same velocity as the hydroxyl maser emission. An H ii region was detected 12'' from the OH maser position, and another, weaker, radio continuum object, at the position of the OH masers. Strong, extended near-IR emission was also found. Synoptic monitoring of the OH maser flux density during the period 1980.6 to 1981.4 revealed little change in peak flux, which may indicate that the masers have become saturated. VLBI observations of the OH maser emission indicate a relatively large angular size, which is interpreted as evidence for interstellar scattering. The observations suggest a region of active star formation associated with a giant molecular cloud at a distance of approximately 6.5 kpc. The H/sub 2/O/OH maser site is likely associated with an OB star in an early evolutionary state.