Searching for cataclysmic variable stars in unidentified X-ray sources

TL;DR

This study searches for new cataclysmic variable stars in unidentified X-ray sources using photometric data, identifying several candidates and highlighting the potential for missed CVs with X-ray emission lacking frequent outbursts.

Contribution

The paper introduces a method combining Gaia data with light curves from multiple surveys to identify new CV candidates, including eclipsing and polar systems, expanding the known population.

Findings

Identified 8 CV candidates, 6 of which are new.

Discovered two eclipsing systems linked to X-ray sources.

Found potential polar candidates within the period gap.

Abstract

We carry out a photometric search for new cataclysmic variable stars (CVs), with the goal of identification for candidates of AR~Scorpii-type binary systems. We select GAIA sources that are likely associated with unidentified X-ray sources, and analyze the light curves taken by the Zwicky Transient Facility, Transiting Exoplanet Survey Satellite, and Lulin One-meter Telescope in Taiwan. We investigate eight sources as candidates for CVs, among which six sources are new identifications. Another two sources have been recognized as CVs in previous studies, but no detailed investigations have been done. We identify two eclipsing systems that are associated with an unidentified XMM-Newton or Swift source, and one promising candidate for polar associated with an unidentified ASKA source. Two polar candidates may locate in the so-called period gap of a CV, and the other six candidates have an orbital period shorter than that of the period gap. Although we do not identify a promising candidate for AR~Scorpii-type binary systems, our study suggests that CV systems that have X-ray emission and do not show frequent outbursts may have been missed in previous surveys.