An unusually powerful and long-lasting water maser flare phenomenon in IRAS 16293-2422

¹ Radio Astronomy Laboratory of Crimean Astrophysical Observatory, Katsively, RT-22, Crimea  
e-mail: volvach@meta.ua
² Astro Space Center, Lebedev Physical Institute, Russian Academy of Sciences, Profsoyuznaya ul. 84/32, Moscow 117997, Russia

Received: 19 May 2022
Accepted: 8 March 2023

Abstract

Aims. Our goal is to obtain new detailed observational data on the water maser flare phenomenon, unprecedented in power and duration, that occurred in IRAS 16293-2422 and determine the physical characteristics of the individual flares.

Methods. We used the ground-based 22 m radio telescope to conduct long-term observations of the water maser features near – 1.5 km s⁻¹ in IRAS 16293-2422. The movement of the radio telescope, collection of observational data, and processing were performed automatically. We used spectral-temporal data analysis to identify water maser flares in a complex flare phenomenon and determine their physical parameters.

Results. The detected maser emission came from the largest structure of maser spots, the high density of which resulted in their partial overlap in time. There were a total of ten individual powerful flares in the phenomenon. The existence of such a complex configuration of emitting maser spots with very similar radial velocities has been confirmed for the first time. We were able to determine that masers of the powerful flares were in an unsaturated state due to a cascade pumping of radiation from several masers located in the observer’s line of sight. We obtained new important physical parameters of maser flares: the detailed shape of flares, the state of the water maser during flares, the H₂O kinetic temperature, the density of the medium, the degree of ionization, and the velocities of the maser spots responsible for the flares.