First Lunar Occultation Results with the TIRCAM2 Near-Infrared Imager at the Devasthal 3.6-m Telescope

TL;DR

This paper reports the first lunar occultation observations using the TIRCAM2 near-infrared imager at the Devasthal 3.6-m telescope, demonstrating its capability for high-speed photometry and stellar measurements, with potential for extensive future observations.

Contribution

It introduces the use of TIRCAM2 for lunar occultation measurements, detailing the instrument setup, data analysis, and initial results including binary star and stellar diameter measurements.

Findings

Detected a small-separation binary star.

Measured two stellar angular diameters.

LO technique can detect sources down to K~9 mag with SNR=1.

Abstract

TIRCAM2 is the facility near-infrared Imager at the Devasthal 3.6-m telescope in northern India, equipped with an Aladdin III InSb array detector. We have pioneered the use of TIRCAM2 for very fast photometry, with the aim of recording Lunar Occultations (LO). This mode is now operational and publicly offered. In this paper we describe the relevant instrumental details, we provide references to the LO method and the underlying data analysis procedures, and we list the LO events recorded so far. Among the results, we highlight a few which have led to the measurement of one small-separation binary star and of two stellar angular diameters. We conclude with a brief outlook on further possible instrumental developments and an estimate of the scientific return. In particular, we find that the LO technique can detect sources down to K~ 9 mag with SNR=1 on the DOT telescope. Angular diameters larger than ~ 1 milliarcsecond (mas) could be measured with SNR above 10, or K~6 mag. These numbers are only an indication and will depend strongly on observing conditions such as lunar phase and rate of lunar limb motion. Based on statistics alone, there are several thousands LO events observable in principle with the given telescope and instrument every year.