Accurate Treatment of Comptonization in X-ray Illuminated Accretion Disks
Abstract
A large fraction of accreting black hole and neutron star systems present clear evidence of the reprocessing of X-rays in the atmosphere of an optically thick accretion disk. The main hallmarks of X-ray reflection include fluorescent K-shell emission lines from iron (~6.4–6.9 keV), the absorption iron K-edge (~7–9 keV), and a broad featureless component known as the Compton hump (~20–40 keV). This Compton hump is produced as the result of the scattering of high-energy photons (E ≳ 10 keV) of the relatively colder electrons (T_e ~ 10⁵–10⁷ K) in the accretion disk, in combination with photoelectric absorption from iron. The treatment of this process in most current models of ionized X-ray reflection has been done using an approximated Gaussian redistribution kernel. This approach works sufficiently well up to ~100 keV, but it becomes largely inaccurate at higher energies and at relativistic temperatures (T_e ~ 10⁹ K). We present new calculations of X-ray reflection using a modified version of our code xillver, including an accurate solution for Compton scattering of the reflected unpolarized photons in the disk atmosphere. This solution takes into account quantum electrodynamic and relativistic effects allowing the correct treatment of high photon energies and electron temperatures. We show new reflection spectra computed with this model, and discuss the improvements achieved in reproducing the correct shape of the Compton hump, the discrepancies with previous calculations, and the expected impact of these new models in the interpretation of observational data.
Additional Information
© 2020 The American Astronomical Society. Received 2020 March 14; revised 2020 May 7; accepted 2020 May 8; published 2020 July 2. This work was been partially supported under NASA No. NNG08FD60C. J.A.G. acknowledges support from NASA ATP grant No. 80NSSC20K0540 and from the Alexander von Humboldt Foundation. E.K.S and J.W. have been supported by DFG grant WI 1860/11-1. A.R., J.M., and A.M. were supported by grants No. 2015/17/B/ST9/03422 and 2015/18/M/ST9/00541 from the Polish National Science Center. software xillver (García & Kallman 2010; García et al. 2013), Matplotlib (version 3.1.3, Hunter 2007), NumPy (version 1.18.1, Oliphant 2006).Attached Files
Published - García_2020_ApJ_897_67.pdf
Submitted - 2005.04852.pdf
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Additional details
- Eprint ID
- 103713
- Resolver ID
- CaltechAUTHORS:20200604-151447853
- NASA
- NNG08FD60C
- NASA
- 80NSSC20K0540
- Alexander von Humboldt Foundation
- Deutsche Forschungsgemeinschaft (DFG)
- WI 1860/11-1
- National Science Centre (Poland)
- 2015/17/B/ST9/03422
- National Science Centre (Poland)
- 2015/18/M/ST9/00541
- Created
-
2020-06-05Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department, Space Radiation Laboratory