Molecular maser radio emission in the environment of young stellar objects (Review)

A brief review of properties of molecular maser sources in star‐forming regions is given. Different types of sources, their structure and variability are discussed. The variability of H 2 O masers at a timescale of several days observed in the case of the Cep A maser source is difficult to explain in the model of energy diffusion inside a maser cloud. Another possibility is suggested and analysed. An H 2 O maser flare may be due to amplification of a strong nonthermal radio flare of the magnetically active central young star (possibly, of the T Tauri variability type) by an initially unsaturated H 2 O maser. An observational test is suggested.