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The Problem of the High Iron Abundance in Accretion Disks around Black Holes

García, J. A. and Kallman, T. R. and Bautista, M. and Mendoza, C. and Deprince, J. and Palmeri, P. and Quinet, P. (2018) The Problem of the High Iron Abundance in Accretion Disks around Black Holes. In: Workshop on Astrophysical Opacities. Astronomical Society of the Pacific Conference Series. No.515. Astronomical Society of the Pacific , San Francisco, CA, pp. 282-288. ISBN 978-1-58381-914-2.

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In most accreting black-hole systems the copious X-rays commonly observed from the inner-most regions are accompanied by a reflection spectrum. The latter is the signature of energetic photons reprocessed by the optically thick material of an accretion disk. Given their abundance and fluorescence yield, the iron K-shell lines are the most prominent features in the X-ray reflected spectrum. Their line profiles can be grossly broadened and skewed by Doppler effects and gravitational redshift. Consequently, modeling the reflection spectrum provides one of the best methods to measure, among other physical quantities, the black-hole spin. At present the accuracy of the spin estimates is called into question because the data fits require very high iron abundances: typically several times the solar value. No plausible physical explanation has been concurrently proffered for these black-hole systems to be so iron rich. The most likely explanation for the supersolar iron abundances is model shortfall at very high densities (>10^(18) cm^(–3)) due to atomic data shortcomings in this regime. We review the current observational evidence for the iron supersolar abundance in many black-hole systems, and show the effects of high density in state-of-the-art reflection models. We also briefly discuss our current efforts to produce new atomic data for high-density plasmas, which are required to refine the photoionization models.

Item Type:Book Section
Related URLs:
URLURL TypeDescription Paper
García, J. A.0000-0003-3828-2448
Kallman, T. R.0000-0002-5779-6906
Deprince, J.0000-0002-3409-8232
Additional Information:© 2018 Astronomical Society of the Pacific. This project is currently being funded by the NASA Astrophysics Research and Analysis Program, grant 80NSSC17K0345. JAG acknowledges support from the Alexander von Humboldt Foundation. JD is a Research Fellow of the Belgian Fund for Research Training in Industry and Agriculture (FRIA). PP and PQ are, respectively, Research Associate and Research Director of the Belgian Fund for Scientific Research (FRS-FNRS).
Funding AgencyGrant Number
Alexander von Humboldt FoundationUNSPECIFIED
Fonds pour la Formation à la Recherche dans l’índustrie et dans l’Ágriculture (FRIA)UNSPECIFIED
Fonds de la Recherche Scientifique (FNRS)UNSPECIFIED
Series Name:Astronomical Society of the Pacific Conference Series
Issue or Number:515
Record Number:CaltechAUTHORS:20180906-133850023
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89421
Deposited By: Tony Diaz
Deposited On:07 Sep 2018 00:16
Last Modified:03 Oct 2019 20:16

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