Study of Complex Absorption and Reflection in a Unique Intermediate Polar Paloma

TL;DR

This study provides a detailed broadband X-ray analysis of the intermediate polar Paloma, revealing complex absorption features, phase-dependent variations, and insights into the accretion processes and white dwarf properties.

Contribution

It introduces a comprehensive spectral modeling approach for Paloma, including multiple partial covering absorbers and reflection analysis, enhancing understanding of accretion dynamics in intermediate polars.

Findings

Complex intrinsic absorber varies with orbital phase.

Shock temperature indicates white dwarf mass of ~0.74 M_sun.

Weak Compton reflection observed in the spectrum.

Abstract

We present the broadband (0.3-40.0 keV) X-ray analysis of a unique intermediate polar Paloma using simultaneous data from XMM-Newton and NuSTAR observatories. The X-ray power spectra show strong modulations over orbital period compared to spin period. The orbit folded lightcurves show single broad hump like structure with strong dips for soft to medium X-rays (0.3-10.0 keV). The energy dependent dips at $\phi \sim 0.16$ and $0.5$ arise due to complex intrinsic absorber, strong enough to have effect well around 15 keV. The absorber could potentially be contributed from accretion curtain/ accretion stream and absorbing material produced by stream-disc/stream-magnetosphere interactions. We notice significant variation of the absorber with orbital phase, with maximum absorption during orbital phase 0.1-0.22. The absorber requires more than one partial covering absorber component, specifying the necessity to use distribution of column densities for spectral modelling of the source. Isobaric cooling flow component is utilized to model the emission from the multi-temperature post-shock region, giving shock temperature of $31.7_{-3.5}^{+3.3}$keV, which corresponds to white dwarf mass of $0.74_{-0.05}^{+0.04}\;M_{\odot}$. We have used both the neutral absorber and the warm absorber models, which statistically give similarly good fit, but with different physical implications. Among the Fe K$_{\alpha}$ line complex, the neutral line is the weakest. We probed the Compton reflection, and found minimal statistical contribution in the spectral fitting, suggesting presence of weak reflection in Paloma.