Swift J201424.9+152930: discovery of a new deeply eclipsing binary with 491 s and 3.4 h modulations

TL;DR

This paper reports the discovery of a new deeply eclipsing binary system, Swift J201424.9+152930, with 491-second pulsations and a 3.4-hour orbital period, identified as an intermediate polar cataclysmic variable through multi-wavelength observations.

Contribution

The paper presents the first identification of a deeply eclipsing intermediate polar cataclysmic variable with detailed timing and spectral analysis, expanding the known diversity of such systems.

Findings

Discovery of a new deeply eclipsing intermediate polar

Detection of 491 s X-ray pulsations and 3.4 h orbital period

Optical and X-ray spectral analysis supports the white dwarf accretor model

Abstract

We report on the discovery of a new X-ray pulsator, Swift J201424.9+152930 (Sw J2014). Owing to its X-ray modulation at 491 s, it was discovered in a systematic search for coherent signals in the archival data of the Swift X-ray Telescope. To investigate the nature of Sw J2014, we performed multi-wavelength follow-up observations with space-borne (Swift and XMM-Newton) and ground-based (the 1.5-m Loiano Telescope and the 3.6-m Telescopio Nazionale Galileo) instruments. The X-ray spectrum of Sw J2014 can be described by a hard and highly absorbed power law. The optical observations made it possible to single out the optical counterpart to this source, which displays several variable emission lines and total eclipses lasting ~20 min. Total eclipses of similar length were observed also in X-rays. The study of the eclipses, allowed us to infer a second periodicity of 3.44 h, which we interpret as the orbital period of a close binary system. We also found that the period has not significantly changed over a ~7 yr timespan. Based on the timing signatures of Sw J2014, and its optical and X-ray spectral properties, we suggest that it is a close binary hosting an accreting magnetic white dwarf. The system is therefore a cataclysmic variable of the intermediate polar type and one of the very few showing deep eclipses.