Abstract
An H \({}_{2}\) O maser flare detected in July 2023 in the star-forming region DR21OH when monitoring the continuum emission in DR21 with PRAO RT22 is reported. These observations were part of a program to study the characteristics of the antenna and the atmospheric absorption at a wavelength of 1.35 cm. Subsequent access to archival data and new measurements have shown that the detected flare in 2023 was not the only one in the source, and DR21OH is highly variable in the H \({}_{2}\) O line at 22 GHz with a rather unpredictable character. Based on continuum measurements in DR21, we have estimated the effective area of RT22.
