Exploring inside-out Doppler tomography: magnetic cataclysmic variables

TL;DR

This paper introduces inside-out Doppler tomography and flux modulation mapping techniques that improve the visualization of low-velocity and high-velocity emission features in magnetic cataclysmic variables, enhancing interpretability of accretion flows.

Contribution

The paper presents novel inside-out velocity projection and flux modulation mapping methods that better expose emission details in Doppler tomography of magnetic cataclysmic variables.

Findings

Inside-out tomograms better reveal low-velocity emission details.

Inside-out tomograms enhance high-velocity magnetic accretion flow features.

Flux modulation mapping improves the reproduction of input spectra.

Abstract

We present the results of applying our inside-out velocity projection and flux modulation mapping techniques to the Doppler tomography of magnetic cataclysmic variables. The inside-out tomogram is constructed by directly projecting phase-resolved spectra onto the inside-out framework. In addition, our flux modulation mapping technique extracts any information related to the modulation of the line flux by utilising consecutive half-phase tomograms. We apply this to both the standard and the inside-out techniques. Our test cases, the polars HU Aqr and V834 Cen, and the intermediate polar PQ Gem, were chosen because of their known accretion characteristics, namely ballistic, magnetic and curtain dominated accretion, respectively. In all three cases the inside-out tomogram better exposes low-velocity emission details which are overly compacted in the standard tomogram. This is especially apparent for the mid-inclination V834 Cen where the almost blob-like blended lower velocity emission in the standard tomogram is more exposed in the inside-out tomogram, making it easier to distinguish between the ballistic and magnetically confined accretion flows that are evident in the trailed spectra. Similarly, the inside-out tomogram enhances high velocity emission details which are washed out in the standard tomogram. This is particularly effective in revealing the high velocity magnetic accretion flows in the polars HU Aqr and V834 Cen. The addition of our flux modulation technique gives a significant improvement in reproducing the trailed input spectra adding more confidence to the interpretation of the Doppler maps. Furthermore, amplitude and phase maps are constructed that further reveal amplitude and phasing characteristics of the emission components in the three test cases.