Lunar Occultations of Eighteen Stellar Sources from the 2.4-m Thai National Telescope

TL;DR

This study reports lunar occultation observations of 18 stars using the Thai National Telescope, detecting four angular diameters and two binary stars, with many measurements being first-time determinations and high angular resolution achieved.

Contribution

First-time lunar occultation measurements of stellar diameters and binaries using the 2.4-m Thai National Telescope with high angular resolution.

Findings

Detected four stellar angular diameters and two binary stars.

Achieved resolution of angular diameters as small as 2 mas.

Identified a new secondary in o Psc and refined orbital parameters for 31 Ari.

Abstract

We report further results from the program of lunar occultation (LO) observations started at the 2.4-m Thai National Telescope (TNT) in 2014. We have recorded LO events of 18 stellar sources, leading to the detection of four angular diameters and two binary stars. With two exceptions, these are first-time determinations. We could resolve angular diameters as small as 2 milliarcseconds (mas) and projected separations as small as 4mas. We discuss the individual results, in the context of previous observations when available. The first-time angular diameters for o Psc, HR 6196 and 75 Leo are in good agreement with expected values, while that of Pi Leo agrees with the average of previous determinations but has a higher accuracy. We find a new secondary in o Psc, as previously suspected from Hipparcos data. We also obtain an accuratemeasurement of the companion in 31 Ari, revealing inconsistencies in the currently available orbital parameters. The TNT, equipped with the fast ULTRASPEC imager, is the leading facility in Southeast Asia for high time resolution observations. The LO technique at this telescope achieves a sensitivity of i up to 10mag, with a potential to detect several hundreds of LO events per year.