DOI

https://doi.org/10.48717/tz6t-ke53

Project

EN015

Title

Mapping the circumstellar OH masers of NSV17351

Abstract

We propose a single-epoch VLBI observation of 1612MHz OH maser in the circumstellar envelope (CSE) of an extreme-OH/IR star NSV17351. After detection of OH maser 46 years ago, we could not find any detection of the masers. Interestingly, we found an acceleration in the spectrum of H2O maser around the same star over 40 years, whose terminal velocity is comparable to that of the OH masers found in 1978. We interpret this result as indicating that H2O gas has been accelerated to a terminal velocity and transported to the outermost region of stellar envelope. It is predicted that the H2O molecules in the transported gas will soon be photodissociated, and the OH maser will be brightened again. As expected, in 15 May 2024, we detected 1612 MHz OH maser (~400 mJy) in a TNRT 40m single-dish observation. Purpose of this EVN proposal is to obtain morphology of the detected OH maser and to compare their positions with those of the H2O masers to confirm the proposed scenario of CSE mass transfer and acceleration. Since the source has a time variability and we are at or near the OH maser maximum, early VLBI observation is preferred.