Evolution of superflares of H2O maser emission in IRAS 16293–2422

Abstract

The aim of this work was to continue the monitoring of the H2O maser emission in IRAS 16293–2422 to detect superflares. We have been observing H2O maser emission at a wavelength of 1.35 cm towards the source IRAS 16293–2422 since 1999. The observations have been carried out with the 22-m radio telescope of the Pushchino Radio Astronomy Observatory (Russia). In 2007–2018, we also conducted several sessions of observations in OH lines at a wavelength of 18 cm in both circular polarizations with the Nançay Radio Telescope (France). Between 1997 and 2021, we observed three cycles of high activity of the H2O maser with a period of 8 yr. This variability could be related to the changing activity of the protostar in the tight binary system of IRAS 16293–2422 in the process of its formation. This variability could be related to an increase in the activity of the tight binary protostar IRAS 16293–2422 A, first seen in 2002. The H2O maser variation in flux density and radial velocity suggests that disturbances are propagating through organized structures in the form of chains ∼3.5 au long, with monotonic velocity gradients in the direction of propagation. The 18-cm OH emission in the main and satellite lines is thermal.