Classifying IGR J18007-4146 as an intermediate polar using XMM and NuSTAR

TL;DR

This study confirms IGR J18007-4146 as an intermediate polar type cataclysmic variable using simultaneous XMM-Newton and NuSTAR observations, revealing its white dwarf's spin period, spectral characteristics, and mass.

Contribution

First detailed multi-instrument analysis classifying IGR J18007-4146 as an intermediate polar CV with spectral modeling and white dwarf mass measurement.

Findings

Detected a 424.4 s spin period of the white dwarf.

Modeled the X-ray spectrum with thermal bremsstrahlung and soft blackbody components.

Measured the white dwarf mass as approximately 1.06 solar masses.

Abstract

Many new and unidentified Galactic sources have recently been revealed by ongoing hard X-ray surveys. A significant fraction of these have been shown to be the type of accreting white dwarfs known as cataclysmic variables (CVs). Follow-up observations are often required to categorize and classify these sources, and may also identify potentially unique or interesting cases. One such case is IGR J18007-4146, which is likely a CV based on follow-up Chandra observations and constraints from optical/IR catalogs. Utilizing simultaneous XMM-Newton and NuSTAR observations, as well as the available optical/IR data, we confirm the nature of IGR J18007-4146 as an intermediate polar type CV. Timing analysis of the XMM data reveals a periodic signal at 424.4 +/- 0.7 s that we interpret as the spin period of the white dwarf. Modeling the 0.3-78 keV spectrum, we use a thermal bremsstrahlung continuum but require intrinsic absorption as well as a soft component and strong Fe lines between 6 and 7 keV. We model the soft component using a single-temperature blackbody with kT = 73 +8/-6 eV. From the X-ray spectrum, we are able to measure the mass of the white dwarf to be 1.06 +0.19/-0.10 Msun, which means IGR J18007-4146 is more massive than the average for magnetic CVs.