DETECTION OF FORMALDEHYDE MASER EMISSION NEAR THE ULTRACOMPACT H-II REGION G29.96-0.02

Using the VLA we have discovered the third Galactic source showing mas er emission in the 6 cm transition of H2CO toward the molecular enviro nment of the cometary ultracompact H II region G29.96-0.02. The maser appears projected against a dense, hot core traced by high-excitation ammonia emission that also has associated water masers. The luminosity of the new maser is comparable to the values found for the H2CO maser s in the Sgr B2 region. High-sensitivity observations toward seven oth er star-forming regions did not reveal any additional maser, confirmin g that H2CO maser emission is indeed a rare phenomenon.