On the Non-relativistic Origin of Red-skewed Iron Lines in CV, Neutron Star and Black Hole Sources

Abstract

We perform the analysis of the iron K_alpha lines detected in three sources representing of three types of accreting compact sources: cataclysmic variable (CV) GK Per, neutron star (NS) Serpens X-1 and black hole (BH) GX 339-4. We find, using data from Epic-PN Camera on-board XMM-Newton observatory,that the iron K_alpha emission line in GK Per has a noticeable red-skewed profile. We compare the GK Per asymmetric line with the red-skewed lines observed by XMM-Newton in Serpens X-1 and GX 339-4. The observation of the K_alpha emission with red-skewed features in CV GK Per cannot be related to the redshift effects of General Relativity (GR). Therefore, if the mechanism of the K_alpha-line formation is the same in CVs, NSs and BHs then it is evident that the GR effects would be ruled out as a cause of red skewness of K_alpha line. The line reprocessing in an outflowing wind has been recently suggested an alternative model for a broad red-shifted iron line formation. In the framework of the outflow scenario the red-skewed iron line is formed in the strong extended wind due to its illumination by the radiation emanating from the innermost part of the accreting material. In this Paper we demonstrate that the asymmetric shapes of the lines detected from these CV, NS and BH sources are well described with the wind (outflow) model. While this fact is hard to reconcile with the relativistic models, it is consistent with the outflowing gas washing out high frequency modulations of the radiation presumably originated in the innermost part of the source.

24 pages, 4 Tables, 9 figures, Accepted for publication in ApJ

References in corpus (6)

• X-ray Properties of Black-Hole Binaries
• Relativistic X-ray Lines from the Inner Accretion Disks Around Black Holes
• Relativistic iron emission lines in neutron star low-mass X-ray binaries as probes of neutron star radii
• Evidence of a Broad Relativistic Iron Line from the Neutron Star Low-Mass X-ray Binary Serpens X-1
• Effects of Downscattering on the Continuum and Line Spectra in Powerful Wind Environment. Monte Carlo Simulations, Analytical Results and Data Analysis
• Compton Scattering of Fe K alpha Lines in Magnetic Cataclysmic Variables

Cited by in corpus (6)

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• Broad iron emission line and kilohertz quasi-periodic oscillations in the neutron star system 4U 1636-53
• Red-skewed K$\alpha$ iron lines in GX 13+1
• Comptonization as an origin of the continuum in Intermediate Polars