Searching for the orbital period of the ultraluminous X-ray source NGC 1313 X-2

TL;DR

This study investigates the potential 6-day orbital period of the ultraluminous X-ray source NGC 1313 X-2 using extensive photometric data, but finds only marginal evidence for this periodicity.

Contribution

The paper provides a detailed analysis of long-term photometric data to search for orbital modulation in NGC 1313 X-2, highlighting the challenges in confirming such periodicity.

Findings

Detected a ~6 day periodicity with >3 sigma significance in B band

No significant periodicity detected in V band

The periodicity detection is 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 day 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.