ИСТИНА

We present the review of the results on Class I methanol masers detected in low-mass star forming regions (LMSFRs). These masers, called further LMMIs, are associated with postshock gas in the lobes of chemically active outflows in LMSFRs NGC1333, NGC2023, HH25, and L1157. LMMI luminosities at 44 GHz match the relation "maser luminosity–protostar luminosity", established earlier for high- and intermediate-mass protostars. No variability of LMMIs have been found in 2004–2011. VLA observations of NGC1333I4A, HH25MMS, and L1157 at 44 GHz demonstrate that the maser images consist of compact spots, unresolved or barely resolved with a spatial resolution of 0.2 arcsec. The brightness temperatures of the strongest spots are hundreds of thousands Kelvins. Many spots consist of two spatial components and exhibit double spectral lines. Some spots demonstrate broad (3-5 km/s) spectral lines with the brightness temperatures about 1000 K. Thus, in spite of large linewidths, these objects could be weak masers. We believe that turbulence plays an important role in forming the image and the spectrum of maser emission. However, LMMI properties cannot be explained within the frames of already published models of methanol masers in turbulent medium. Therefore some additional factors are required in order to explain the observed LMMI properties.