X-ray emissions from two-temperature accretion flows within a dipole magnetic funnel

TL;DR

This study models two-temperature accretion flows in magnetic funnel geometries, revealing that such effects produce harder X-ray spectra and influence white dwarf mass estimates in magnetic cataclysmic variables.

Contribution

It introduces a two-temperature hydrodynamic model within a dipolar magnetic funnel, improving understanding of X-ray emissions and mass estimates in magnetic accretion systems.

Findings

Two-temperature effects harden keV X-ray spectra.

Dipolar geometry yields harder spectra than planar models.

Including these effects reduces white dwarf mass estimates by up to 9%.

Abstract

We investigate the hydrodynamics of accretion channelled by a dipolar magnetic field (funnel flows). We consider situations in which the electrons and ions in the flow cannot maintain thermal equilibrium (two-temperature effects) due to strong radiative loss, and determine the effects on the keV X-ray properties of the systems. We apply this model to investigate the accretion shocks of white dwarfs in magnetic cataclysmic variables. We have found that the incorporation of two-temperature effects could harden the keV X-rays. Also, the dipolar model yields harder X-ray spectra than the standard planar model if white dwarf is sufficiently massive (>~1M_sun). When fitting observed keV X-ray spectra of magnetic cataclysmic variables, the inclusion of two-temperature hydrodynamics and a dipolar accretion geometry lowers estimates for white-dwarf masses when compared with masses inferred from models excluding these effects. We find mass reductions <~9% in the most massive cases.