Optical variability of the ultraluminous X-ray source NGC 1313 X-2

TL;DR

This study investigates optical variability in the ultraluminous X-ray source NGC 1313 X-2, finding a tentative 6-day periodicity in B band data with limited statistical significance and no V band detection.

Contribution

It provides the longest phase-connected photometric analysis of NGC 1313 X-2, assessing the presence of a previously reported 6-day modulation.

Findings

Possible 6-day periodicity in B band with >3 sigma significance

No significant detection of the modulation in V band

The periodicity detection remains uncertain due to low significance

Abstract

We analyzed the longest phase-connected photometric dataset available for NGC 1313 X-2, looking for the ~6 day modulation reported by Liu et al. (2009). The folded B band light curve shows a 6 days periodicity with a significance slightly larger than 3 sigma. The low statistical significance of this modulation, along with the lack of detection in the V band, make its identification uncertain.