Properties of the Galactic population of cataclysmic variables in hard X-rays

TL;DR

This study characterizes the spatial distribution and hard X-ray luminosity function of galactic cataclysmic variables, revealing their significant contribution to galactic X-ray emission and their properties compared to previous lower-energy studies.

Contribution

It provides the first comprehensive measurement of the hard X-ray luminosity function and spatial distribution of CVs using INTEGRAL data, confirming consistency with lower-energy results.

Findings

Most CVs detected are intermediate polars with luminosities 10^{32}-10^{34} erg/sec.

The scale height of CVs in the Galactic disk is approximately 130 pc.

CVs contribute significantly to the galactic hard X-ray luminosity density.

Abstract

We measure the spatial distribution and hard X-ray luminosity function of cataclysmic variables (CVs) using the INTEGRAL all-sky survey in the 17-60 keV energy band. The vast majority of the INTEGRAL detected CVs are intermediate polars with luminosities in the range 10^{32}-10^{34} erg/sec. The scale height of the Galactic disk population of CVs is found to be 130{+90}{-50} pc. The CV luminosity function measured with INTEGRAL in hard X-rays is compatible with that previously determined at lower energies (3--20 keV) using a largely independent sample of sources detected by RXTE (located at |b|>10deg as opposed to the INTEGRAL sample, strongly concentrated to the Galactic plane). The cumulative 17-60 keV luminosity density of CVs per unit stellar mass is found to be (1.3+/-0.3)x10^{27} erg/sec/Msun and is thus comparable to that of low-mass X-ray binaries in this energy band. Therefore, faint but numerous CVs are expected to provide an important contribution to the cumulative hard X-ray emission of galaxies.