Astron. Astrophys. Suppl. Ser. 147, 181-185

New detections of OH sources towards the 6.7 GHz methanol masers

M. Szymczak - A.J. Kus

Send offprint request: M. Szymczak

Torun Centre for Astronomy, Nicolaus Copernicus University, ul. Gagarina 11, PL-87100 Torun, Poland

Received May 29; accepted September 14, 2000

Abstract:

A sample of 6.7 GHz methanol masers has been searched for OH maser emission at 1665 and 1667 MHz using the 32 m Torun radio telescope. Eight new OH sources were detected. They are generally weak at radio and infrared wavelengths. In the northern hemisphere sample of 68 methanol sources the OH maser emission is associated with 49 sources. Generally OH masers do not arise in weak FIR sources. The ratio of OH to CH₃OH maser flux densities increases for objects with blue FIR colour and probably reflects evolutionary changes in the star-forming regions.

Key words: masers -- surveys -- stars: formation -- ISM: molecules -- radio lines: ISM -- HII regions