Long-term monitoring and interpretation of flares in the H2O maser emission of IRAS 16293–2422

Abstract

The results of a study of the H2O and OH maser emission from the cool IR source IRAS 16293−2422 are presented. The observations analyzed were obtained in H2O lines with the 22-m telescope of the Pushchino Radio Astronomy Observatory during 1999–2015 and in OH lines with the Nanc¸ ay radio telescope (France). A large number of very strong flares of the H2O maser were detected, reaching fluxes of tens of thousands of Jansky. Individual features can form organized structures resembling chains ∼2 AU in length with a radial-velocity gradient along them. The observed drift of the H2O emission (2003–2004) in space and velocity (from 4.3 to 5.3 km/s) is not due solely to proper motion of the features. The other origin of the drift is a drift of the emission maximum during a flare as the shock consecutively excites spatially separated features in the structure in the form of a chain. The OH-line observations at 18 cm show that the emission remains unpolarized and thermal, with a line width of 0.7 km/s, which corresponds to a cloud temperature of ∼30 K.