Spectral and polarization properties of reflected X-ray emission from black hole accretion discs

Abstract

X-ray polarimetric missions planned for this decade will significantly enhance our knowledge of compact accreting sources. Observations of the X-ray polarization signal from active galactic nuclei (AGNs) or X-ray binary systems (XRBs) will bring new means to study inner accretion flow in these objects that, together with currently used spectroscopic and timing techniques, will help us to determine better their properties, such as their inclination, orientation, shape, and size of their corona as well as the black hole spin. In this work, we present a yet missing piece in the global polarization models of black hole accretion discs. We compute the reflected X-ray emission from the disc in a local co-moving frame using (1) the radiative transfer code TITAN to obtain the ionization structure of the disc and (2) the Monte Carlo code STOKES that incorporates the physics of absorption, re-emission, and Compton scattering to produce a complete spectropolarimetric output. We present the final Stokes parameters I, Q, and U for a set of photon-indices of the incident primary power-law radiation, the disc ionization parameters, incident and emission angles, for three independent polarization states of the incident coronal X-ray photons with a sufficient resolution in energy to allow for sharp discussion of spectral and polarization properties. We show that the spectral component matches well literature predictions. The polarization degree and angle are in agreement with analytical approximations previously appearing in reflection models and we demonstrate that the polarized reflected X-ray emission can be, locally, quite large in the 2-12 keV band.

13 pages, 9 figures, published in MNRAS. Version 2, corrected for a small error in Section 3.2 (in the last sentence of the 6th paragraph)

References in corpus (11)

• X-ray Properties of Black-Hole Binaries
• Modelling the behaviour of accretion flows in X-ray binaries
• X-ray reflection in accreting stellar-mass black hole systems
• Thermal disc emission from a rotating black hole: X-ray polarization signatures
• A compendium of AGN inclinations with corresponding UV/optical continuum polarization measurements
• Polarization signatures of strong gravity in AGN accretion discs
• Modeling optical and UV polarization of AGNs III. From uniform-density to clumpy regions
• The X-ray Polarization of the Accretion Disk Coronae of Active Galactic Nuclei
• A hard look at thermal reverberation and optical/UV lags in NGC 5548
• Spectral and polarization properties of black hole accretion disc emission: including absorption effects
• Accurate Treatment of Comptonization in X-ray Illuminated Accretion Disks

Cited by in corpus (12)

• Polarized x-rays constrain the disk-jet geometry in the black hole x-ray binary Cygnus X-1
• Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements
• New Constraints on the Spin of the Black Hole Cygnus X-1 and the Physical Properties of its Accretion Disk Corona
• X-ray Polarization of the Black Hole X-ray Binary 4U 1630-47 Challenges Standard Thin Accretion Disk Scenario
• Ultrasoft state of microquasar Cygnus X-3: X-ray polarimetry reveals the geometry of astronomical puzzle
• A second view on the X-ray polarization of NGC 4151 with IXPE
• Spectral and polarization properties of reflected X-ray emission from black-hole accretion discs for a distant observer: the lamp-post model
• Modeling fast X-ray variability around an accreting black hole
• Investigating the consistency of the shape and flux of X-ray reflection spectra in the hard state with an accretion disk reaching close to the black hole
• Interaction between disk and extended corona in a general relativistic framework
• Accretion Geometry of Black Hole X-ray Binaries: Insights from X-ray Observations
• Shape and ionization of equatorial matter near compact objects from X-ray polarization reflection signatures