A search for photometric variability towards the globular cluster M3 with the TWenty Inch Survey Telescope

TL;DR

This study showcases the capabilities of the TWIST telescope in conducting high-cadence photometric monitoring of globular cluster M3, discovering new variable stars, refining known star measurements, and evaluating the system's performance for time-domain astronomy.

Contribution

The paper introduces the TWIST observatory's first scientific results, including new variable star discoveries, improved measurements of known variables, and a novel flat-field correction technique.

Findings

Discovered four new SX Phoenicis variables in M3.

Updated periods and amplitudes for numerous RR Lyrae stars.

Assessed the observatory's photometric performance and feasibility for microlensing detection.

Abstract

We present the commissioning results and first scientific observations from the newly installed TWIST observatory - a 50 cm telescope equipped with an sCMOS camera providing a $36.1\times24.1$ arcmin$^2$ field of view - housed in the former SuperWASP-North enclosure. We conducted a 67-night, 199-day baseline white-light monitoring campaign centred on the globular cluster M3 aimed at characterizing stellar variability within the cluster while also assessing the photometric performance of the newly commissioned system. We report the discovery of four new SX Phoenicis variables (V301-304), confirm their cluster membership, and identify fundamental-mode pulsation in one, allowing an independent period-luminosity-based distance estimate to M3. We revisited 231 previously known RR Lyrae stars, providing updated period measurements for 203 and white-light amplitudes for 198. We detected Blazhko-like modulation in 53 stars and characterized the modulation parameters for 28. Notably, we measure periods and amplitudes for the unclassified variables V286 and V287 for the first time. We also identify three foreground flaring M dwarfs, and assess the feasibility of detecting microlensing events in M3, concluding that expected rates are negligible. Alongside the scientific results, we introduce a new correction technique for flat-field images affected by scattered light and present a full characterization of the observatory's photometric capabilities. These results demonstrate the scientific utility of TWIST for high-cadence time-domain surveys using modest-aperture instrumentation.