A survey of the 6.7 GHz methanol maser emission from IRAS sources. I. Data

We report the first results of a search for 6.7 GHz methanol masers in the direction of 1399 IRAS objects: north of declination -20 degrees with the flux densities greater than 100 Jy at 60 mu m and the flux density ratio F-60/F-25 > 1. Observations were made with the sensitivity of 1.7 Jy and the velocity resolution of 0.04 km s(-1) using the 32-m Torun radio telescope. Maser emission was found in 182 sources, including 70 new detections. 32 new sources were identified with objects of radio emission associated with star-forming regions. Comparison of the present data set with other observations suggests that about 65% of methanol masers exhibit moderate or strong variations on time-scales of about 4 and 8 years.