Microlensing and Variability in the Bulge of M31

TL;DR

This paper discusses the development of an automatic pipeline for detecting microlensing events in the Andromeda galaxy's bulge, even amidst variable star activity, and presents initial findings from the Angstrom Project.

Contribution

It introduces a novel automatic candidate selection method capable of identifying microlensing events blended with variable stars, enhancing detection capabilities.

Findings

Successful development of an automatic candidate selection pipeline.

Identification and characterization of variable stars in M31.

Detection of a notably short-duration microlensing event.

Abstract

For the past five seasons, the Angstrom Project, an international microlensing collaboration, has been making observations of the central bulge of M31, the Andromeda galaxy, searching for microlensing events. This thesis describes the work that has been done to develop an automatic candidate selection pipeline which enables lensing candidates to be found even if they are blended with periodic variable baseline, something which has never been attempted before in the same way. As a by-product of this process, many variable stars are found and their properties are investigated and characterised. The results of the investigations to date are presented. The final selection of microlensing candidates selected from the most recent Angstrom lightcurve data set is shown, and a separate more detailed investigation into one particularly interesting microlensing candidate of very short duration is described.