# Machine Learning on Difference Image Analysis: A comparison of methods for transient detection

## TL;DR

This paper compares various Difference Image Analysis techniques combined with Machine Learning algorithms for detecting optical transients related to gravitational wave events, evaluating their effectiveness across diverse observational scenarios.

## Contribution

It introduces a comprehensive comparison of DIA methods with ML, including the implementation of Zackay et al.'s technique in an open-source pipeline for transient detection.

## Key findings

- Zackay et al.'s subtraction method performs best among DIA techniques.
- ML algorithms significantly improve transient classification accuracy.
- An optimal combined strategy enhances detection performance.

## Abstract

We present a comparison of several Difference Image Analysis (DIA) techniques, in combination with Machine Learning (ML) algorithms, applied to the identification of optical transients associated with gravitational wave events. Each technique is assessed based on the scoring metrics of Precision, Recall, and their harmonic mean F1, measured on the DIA results as standalone techniques, and also in the results after the application of ML algorithms, on transient source injections over simulated and real data. This simulations cover a wide range of instrumental configurations, as well as a variety of scenarios of observation conditions, by exploring a multi dimensional set of relevant parameters, allowing us to extract general conclusions related to the identification of transient astrophysical events. The newest subtraction techniques, and particularly the methodology published in Zackay et al. (2016) are implemented in an Open Source Python package, named properimage, suitable for many other astronomical image analyses. This together with the ML libraries we describe, provides an effective transient detection software pipeline. Here we study the effects of the different ML techniques, and the relative feature importances for classification of transient candidates, and propose an optimal combined strategy. This constitutes the basic elements of pipelines that could be applied in searches of electromagnetic counterparts to GW sources.