AGAPEROS: Searching for variable stars in the LMC Bar with the Pixel Method. I. Detection, astrometry and cross-identification

TL;DR

This paper applies the Pixel Method to identify and catalog 632 variable stars in the LMC Bar, significantly expanding the known sample of long-term variables by a factor of ten, using a comprehensive, non-periodic selection approach.

Contribution

It introduces an optimized, extensive selection process for variable stars in the LMC Bar, increasing the known sample size and providing detailed catalog data.

Findings

Discovered 632 variable objects, 90% previously undetected.

Expanded the known long-term variable star sample by a factor of 10.

Provided detailed catalog with positions, magnitudes, and blending indicators.

Abstract

We extend the work developed in previous papers on microlensing with a selection of variable stars. We use the Pixel Method to select variable stars on a set of 2.5 x 10**6 pixel light curves in the LMC Bar presented elsewhere. The previous treatment was done in order to optimise the detection of long timescale variations (larger than a few days) and we further optimise our analysis for the selection of Long Timescale and Long Period Variables (LT&LPV). We choose to perform a selection of variable objects as comprehensive as possible, independent of periodicity and of their position on the colour magnitude diagram. We detail the different thresholds successively applied to the light curves, which allow to produce a catalogue of 632 variable objects. We present a table with the coordinate of each variable, its EROS magnitudes at one epoch and an indicator of blending in both colours, together with a finding chart. A cross-correlation with various catalogues shows that 90% of those variable objects were undetected before, thus enlarging the sample of LT&LPV previously known in this area by a factor of 10. Due to the limitations of both the Pixel Method and the data set, additional data -- namely a longer baseline and near infrared photometry -- are required to further characterise these variable stars, as will be addressed in subsequent papers.