Candidate microlensing events from M31 observations with the Loiano telescope

TL;DR

This paper reports on a pixel lensing campaign towards M31 using the Loiano telescope, presenting the second year's results, an automatic detection pipeline, and candidate events consistent with expected self-lensing rates.

Contribution

It introduces an automated pipeline for microlensing detection in M31 and provides the first detailed simulation and efficiency analysis for this observational campaign.

Findings

Detected 1-2 candidate microlensing events

Results align with expected M31 self-lensing rates

Statistics are too low for definitive MACHO conclusions

Abstract

Microlensing observations towards M31 are a powerful tool for the study of the dark matter population in the form of MACHOs both in the Galaxy and the M31 halos, a still unresolved issue, as well as for the analysis of the characteristics of the M31 luminous populations. In this work we present the second year results of our pixel lensing campaign carried out towards M31 using the 152 cm Cassini telescope in Loiano. We have established an automatic pipeline for the detection and the characterisation of microlensing variations. We have carried out a complete simulation of the experiment and evaluated the expected signal, including an analysis of the efficiency of our pipeline. As a result, we select 1-2 candidate microlensing events (according to different selection criteria). This output is in agreement with the expected rate of M31 self-lensing events. However, the statistics are still too low to draw definitive conclusions on MACHO lensing.