DOI

https://doi.org/10.48717/e1mn-s874

Project

EA067

Title

Imaging variable sources from Irbene monitoring program

Abstract

We propose follow-up observations of three methanol maser sources at the 6.7 GHz methanol maser transition, which have been monitored with two Irbene radio telescopes. In the last EVN project (EA063), we obtained phase-referenced images and studied the milliarcsecond structures in detail. Two sources (G90.925+1.486 and G94.602-1.796) showed elongated structures with velocity gradients suggesting rotational discs. The third target, G78.122+3.633, was studied by VLBI earlier, and we could study the variability of single maser cloudlets over 15 yrs. The variability is caused by variance in pumping rate, and maser cloudlets located in the disc are more variable in short and long time scales compared to cloudlets related physically to the disk-jet interface region. Since mid-2021, Irbene monitoring has shown a rapid variability increase in G78. We ask for more data also for this target during the source activity phase in order to constrain possible scenarios of variability. In this project, we aim: i) to study single cloudlet proper motions, ii) to identify cloudlets responsible for the observed variability, and iii) to search for continuum emission.