Significant reflection and absorption effects in the X-ray emission of the Intermediate Polar IGR J17195-4100

Abstract

X-ray emission is from shock-heated plasma in magnetic cataclysmic variables, and is processed by absorption and scattering before reaching the observer. We investigate these effects in the X-ray emission of the Intermediate Polar IGR J17195-4100 by carrying out the X-ray spectral analysis, spin modulation and hardness ratio. We present high-sensitivity broadband X-ray spectral analysis by combining NuSTAR and XMM-Newton observations in the 0.3-78.0 keV energy range. The X-ray spectral analysis is performed using six composite models, including the angle-dependent reflection model (reflect), multi-temperature plasma emission models (CEVMKL, MKCFLOW), and photoionised and/or neutral partially covering absorption models (zxipcf, pcfabs) within XSPEC. We examine also the spin modulation in four energy ranges and the hardness ratio, to determine the absorption and scattering effects. We find that the spectrum is best modelled with a reflection amplitude ($\Omega$) of 0.58 $^{+0.38}_{-0.26}$, an ionisation parameter, log($\xi$), of 1.46$^{+0.44}_{-0.23}$ with an equivalent hydrogen column density of 3.09$^{+2.26}_{-0.68}$ $\times$ 10$^{22}$ cm$^{-2}$, a neutral absorber, and a multi-temperature plasma temperature of 27.14$^{+2.0}_{-2.13}$ keV. In addition, we detect effects of electron scattering in the NuSTAR band, leading to modulation amplitude of about a steady 9$\%$ that increases up to 15$\%$ after 20 keV. We stress that these effects significantly affect the X-ray emission of intermediate polars and should be considered to obtain a good representation of the intrinsic spectrum.