Further milliarcsecond resolution results on cool giants and binary stars from lunar occultations at Devashtal

TL;DR

This study presents high-resolution lunar occultation observations of cool giants and binary stars, including first-time angular diameters and binary detections, using telescopes at Devasthal with near-infrared capabilities.

Contribution

First lunar occultation measurements of angular diameters for late-type giants and binary star separations using the TIRCAM2 camera at Devasthal.

Findings

First angular diameters for two late-type giants

Detection of a new binary star HR 1860

Upper limits as small as 1 milliarcsecond for unresolved sources

Abstract

We report on 26 lunar occultation events observed in the context of a program started at Devasthal in 2017. In addition to the customary observations with the 1.3-m telescope, we report here also the first attempts performed with the TIRCAM2 camera at the 3.6-m DOT telescope in the near-IR. The results consist in the first-time angular diameters for two late-type giants, in a measurement of the well-known AGB pulsating variable SW~Vir, and in the measurement of eight small separation binaries one of which is detected for the first time (HR~1860). We also measured the wider binaries SAO~94431 and 55~Tau (twice). The remaining sources were found to be unresolved with upper limits as small as 1~milliarcsecond. We plan to develop further the high-speed capability of the TIRCAM2 instrument, so as to include in our program also more near-infrared, highly extincted sources.