ИСТИНА

We report the results of our long-term monitoring of the H2O and OH masers toward ``cold’’ IRAS sources in dark molecular clouds. The observations were carried out in 1980-2015 on the 22-metre radio telescope of the Pushchino Radio Astronomy Observatory (Russia) and in 1991-2015 on the radio telescope of the Nançay Radio Astronomy Station (France). Here we discuss the results for 4 sources: IRAS 06308+0402, IRAS 18265-1517, IRAS 18277-1516, and IRAS 20126+4104. We present selected spectra and line parameters. Cyclic variability of the H2O maser emission of the sources on timescales from 1.8 to 5.5 years was detected. We consider models of the H2O maser sources. Strong variability of the OH maser in IRAS 20126+4104 was observed. From the magnitude of the OH line Zeeman splitting the line-of-sight component of the magnetic field was estimated to be 1.3 mG in IRAS 18265-1517 (2008) and 10 mG in IRAS 20126+4104 (2014). In the latter case the magnetic field was found to be variable. In both sources appreciable emission in the 1667 MHz OH line was detected, which is not typical of OH masers in star-forming regions. This requires a revision of the existing OH maser model, i.e., correction of the physical parameters such as gas density and temperature in the OH masering regions.