Distances of Stars by mean of the Phase-lag Method

TL;DR

This paper refines distance measurements of variable OH/IR stars using the phase-lag method, combining long-term radio monitoring and high-resolution mapping to improve understanding of their distribution in different environments.

Contribution

It updates and enhances the phase-lag distance determination technique for AGB stars with circumstellar envelopes, integrating new observational data.

Findings

Refined distances for several OH/IR stars.

Improved constraints on star distribution in the Galaxy and Magellanic Clouds.

Enhanced accuracy of circumstellar envelope measurements.

Abstract

Variable OH/IR stars are Asymptotic Giant Branch (AGB) stars with an optically thick circumstellar envelope that emit strong OH 1612 MHz emission. They are commonly observed throughout the Galaxy but also in the LMC and SMC. Hence, the precise inference of the distances of these stars will ultimately result in better constraints on their mass range in different metallicity environments. Through a multi-year long-term monitoring program at the Nancay Radio telescope (NRT) and a complementary high-sensitivity mapping campaign at the eMERLIN and JVLA to measure precisely the angular diameter of the envelopes, we have been re-exploring distance determination through the phase-lag method for a sample of stars, in order to refine the poorly-constrained distances of some and infer the currently unknown distances of others. We present here an update of this project.