Swift J0525.6+2416 and IGR J04571+4527: two new hard X-ray selected magnetic cataclysmic variables identified with XMM-Newton

TL;DR

This study presents detailed X-ray timing and spectral analysis of two hard X-ray sources, confirming their classification as magnetic cataclysmic variables of the Intermediate Polar type and providing new insights into their white dwarf properties.

Contribution

First high signal-to-noise soft X-ray observations of these sources, enabling precise measurement of white dwarf spin periods and spectral modeling to confirm their IP classification.

Findings

White dwarf spin periods identified: 226.28 s and 1222.6 s.

Spectral fits indicate multi-temperature optically thin emission.

White dwarf masses estimated at approximately 1.1 and 1.0 solar masses.

Abstract

IGR J04571+4527 and Swift J0525.6+2416 are two hard X-ray sources detected in the Swift/BAT and INTEGRAL/IBIS surveys. They were proposed to be magnetic cataclysmic variables of the Intermediate Polar (IP) type, based on optical spectroscopy. IGR J04571+4527 also showed a 1218 s optical periodicity, suggestive of the rotational period of a white dwarf, further pointing towards an IP classification. We here present detailed X-ray (0.3-10 keV) timing and spectral analysis performed with XMM-Newton, complemented with hard X-ray coverage (15-70 keV) from Swift/BAT. These are the first high signal to noise observations in the soft X-ray domain for both sources, allowing us to identify the white dwarf X-ray spin period of Swift J0525.6+2416 (226.28 s), and IGR J04571+4527 (1222.6 s). A model consisting of multi-temperature optically thin emission with complex absorption adequately fits the broad-band spectrum of both sources. We estimate a white dwarf mass of about 1.1 and 1.0 solar masses for IGR J04571+4527 and Swift J0525.6+2416, respectively. The above characteristics allow us to unambiguously classify both sources as IPs, confirming the high incidence of this subclass among hard X-ray emitting Cataclysmic Variables.