2 Observations

The observational data were taken between 1999 October and December with the 32 m Torun telescope equipped with a cooled HEMT dual-channel 1.6 GHz receiver. At this frequency the half-power beam width of the antenna was $22^{\prime}$. The system temperature at the zenith was about 35 K. The observations were made in the total-power position switching mode with a 2¹⁴-channel autocorrelator as spectrometre. The autocorrelator was divided into 4 banks of 4096-channel each to observe both left and right circular polarizations at 1665 and 1667 MHz simultaneously. The observing bandwidth of 1 MHz provided the velocity extent of $\pm 80$ km s^-1 relative to the LSR. The band-centre velocities were the same as the central velocities of the methanol emission observed during the Torun survey (Szymczak et al. 2000). The resulting velocity resolution was 0.1 km s^-1 after Hanning weighting.

The spectra were obtained alternating every 5 minutes between the source position and the offset position displaced by $60^{\prime}$ in right ascension. Several scans made for each source were carefully inspected for the possible occurrence of radio interferences and edited if necessary. Unfortunately, some scans had to be discarded as they were corrupted by strong interferences. A typical integration time of 2 hours on source yielded the rms noise level of 0.2 Jy. The data were calibrated using a reference noise diode, whose value was determined by comparison observations of W12, assuming unpolarized flux densities of 12.2 and 15.1 Jy at 1665 and 1667 MHz respectively. The absolute flux density calibration is accurate within 20%. All newly discovered sources were reobserved to exclude false detection caused by interferences from satellites or the local ones.

In making up the target list we relied upon our own survey of the 6.7 GHz methanol masers (Szymczak et al. 2000). The sample was confined to the objects with $\delta > 0^{\circ}$. All new methanol sources and already known ones with no OH observations reported in the literature were searched for. Some known OH sources were observed as well.