First Lunar Occultation Results from the 2.4 m Thai National Telescope equipped with ULTRASPEC

TL;DR

This paper reports the first lunar occultation observations from the 2.4m Thai National Telescope with ULTRASPEC, demonstrating high time resolution imaging and providing new constraints on stellar companions, thus extending lunar occultation research in Southeast Asia.

Contribution

First lunar occultation results from the Thai National Telescope using ULTRASPEC, showcasing high-speed imaging capabilities and new measurements of stellar binaries in Southeast Asia.

Findings

Stringent limits on the binary companion of α Cnc (<0.003 arcsec, Δm > 5)

Extended coverage and measurements of the binary HR 7072

Assessment of ULTRASPEC's performance for lunar occultation observations

Abstract

The recently inaugurated 2.4\,m Thai National Telescope (TNT) is equipped, among other instruments, with the ULTRASPEC low-noise, frame-transfer EMCCD camera. At the end of its first official observing season, we report on the use of this facility to record high time resolution imaging using small detector subarrays with sampling as fast as several $10^2$\,Hz. In particular, we have recorded lunar occultations of several stars which represent the first contribution to this area of research made from South-East Asia with a telescope of this class. Among the results, we discuss an accurate measurement of $\alpha $~Cnc, which has been reported previously as a suspected close binary. Attempts to resolve this star by several authors have so far met with a lack of unambiguous confirmation. With our observation we are able to place stringent limits on the projected angular separation ($<0\farcs003$) and brightness ($\Delta{\rm m} > 5$) of a putative companion. We also present a measurement of the binary {HR~7072}, which extends considerably the time coverage available for its yet undetermined orbit. We discuss our precise determination of the flux ratio and projected separation in the context of other available data. We conclude by providing an estimate of the performance of ULTRASPEC at TNT for lunar occultation work. This facility can help to extend the lunar occultation technique in a geographical area where no comparable resources were available until now.