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 • with the flux densities greater than 100 Jy at 60 µm 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 Toruń 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 timescales of about 4 and 8 years.

Abstract. We report the results of an unbiased survey for 6.7 GHz methanol maser emission of a ∼21 deg 2 strip of the Galactic plane carried out with the 32 m Toruń radio telescope. An area at 20• ≤ l ≤ 40• , |b| ≤ 0.• 52 was surveyed in an equilateral triangular grid with a sensitivity limit of about 1.6 Jy. We detected a total of 100 sources, 26 of which are new detections. All the new sources are of moderate intensity and their peak flux densities have median value of 6.5 Jy, i.e. about half that of previously known sources in the sample. About 80% of maser sources have IR counterpart candidates within a 1 radius but not all the IRAS counterparts of methanol masers have colours typical of ultracompact HII regions. An excess of masers unassociated with IR sources occurs at 30• because of incompleteness of IR catalogues due to strong confusion near the tangential region of the spiral arm. Our unbiased survey doubled the number of detections as compared to IRAS-based observations. Within the positional uncertainty of 1 about one third of the methanol sources have radio continuum counterparts at 5 GHz of a flux density greater than 2.5-10 mJy. The distribution of methanol sources appears to be consistent with a clustered mode of formation of massive stars.

We report observations of the 4765‐MHz maser transition of OH (2Π1/2, J=1/2, F=1→0) towards 57 star‐forming regions, taken with the 32‐m Toruń telescope. Nine maser sources were detected, of which two had not been reported previously. The newly discovered sources in W75N and Cep A and four previously known sources were monitored over periods ranging from a few weeks to six months. Significant variations of the maser intensity occurred on time‐scales of one week to two months. The relationships between the flux density and the linewidth for the new sources, established during the rise and fall phases of bursts that lasted 6–8 weeks, are consistent with a model of saturated masers.

A sample of 174 methanol sources has been observed with the 32 m Torun radio telescope at four or five epochs separated by 3-7 months. Observations of the 6.7 GHz maser line revealed that about 80% of sources are variable. 20% of sources showed strong variations of the integrated flux density usually on time-scales of 5-12 months. These variations were associated with strong changes in the relative intensities of maser features. Methanol emission from five sources disappeared. The time-scales of variability were longer than 12 months for only 23% of variable sources. It is suggested that the variability of methanol emission is related to the dynamics of the maser regions.

A blind survey for 6.7 GHz methanol maser emission has been made with the 32 m Toruri radio telescope. The survey consists of 4,800 spectra on an equilateral triangular grid pattern with each grid point separated by 4~4 covering a field of rv21 deg 2 at galactic longitudes 20 0to 40 0and galactic latitudes ±0~52. The average sensitivity was 1.6 Jy and the spectral resolution was 0.04 km s-l. A total of 99 sources were detected, 28 of which were not found during previous searches of IRASselected ultracompact HII regions. The peak flux density of new detections is usually lower than 30 Jy. About half of the methanol masers have no IRAS counterparts within a radius of 2'. The nature of these sources is unclear.