Finding the Brightest Galactic Bulge Microlensing Events with a Small Aperture Telescope and Image Subtraction

TL;DR

This study demonstrates that small aperture telescopes combined with image subtraction can effectively detect bright microlensing events in the Galactic bulge, offering a cost-effective monitoring method.

Contribution

It introduces a feasible approach using small telescopes and image subtraction to monitor bright microlensing events, filling a niche in existing survey methods.

Findings

Successfully matched 7 microlensing events from OGLE archives.

Detected several candidate microlensing-like light curves.

Approximately 50% of variable stars found are new discoveries.

Abstract

Following the suggestion of Gould and Depoy (1998) we investigate the feasibility of studying the brightest microlensing events towards the Galactic bulge using a small aperture (~10 cm) telescope. We used one of the HAT telescopes to obtain 151 exposures spanning 88 nights in 2005 of an 8.4x8.4 square degree FOV centered on (l,b) = (2.85, -5.00). We reduced the data using image subtraction software. We find that such a search method can effectively contribute to monitoring bright microlensing events, as was advocated. Comparing this search method to the existing ones we find a dedicated bulge photometric survey of this nature would fulfill a significant niche at excellent performance and rather low cost. We obtain matches to 7 microlensing events listed in the 2005 OGLE archives. We find several other light curves whose fits closely resemble microlensing events. Unsurprisingly, many periodic variables and miscellaneous variables are also detected in our data, and we estimate approximately 50% of these are new discoveries. We conclude by briefly proposing Small Aperture Microlensing Survey, which would monitor the Galactic bulge around the clock to provide dense coverage of the highest magnification microlensing events.