The Cluster AgeS Experiment (CASE). Detecting Photometric Variability with the Friends of Friends Algorithm

TL;DR

This paper adapts the friends of friends algorithm to analyze light curves for transient phenomena, demonstrating high detection efficiency and discovering new variable stars in a globular cluster.

Contribution

It introduces a novel application of the friends of friends algorithm to photometric light curve analysis for variable star detection.

Findings

Achieved up to 100% detection efficiency for dwarf novae

Narrowed search to 1% of data with 90% efficiency

Discovered 28 new variables in globular cluster M22

Abstract

We adapt the friends of friends algorithm to the analysis of light curves, and show that it can be successfully applied to searches for transient phenomena in large photometric databases. As a test case we search OGLE-III light curves for known dwarf novae. A single combination of control parameters allows to narrow the search to 1% of the data while reaching a $\sim$90% detection efficiency. A search involving $\sim$2% of the data and three combinations of control parameters can be significantly more effective - in our case a 100% efficiency is reached. The method can also quite efficiently detect semi-regular or strictly periodic variability. We report 28 new variables found in the field of the globular cluster M22, which was examined earlier with the help of periodicity-searching algorithms