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Photoionization Models for High-density Gas

Kallman, T. and Bautista, M. and Deprince, J. and García, J. A. and Mendoza, C. and Ogorzalek, A. and Palmeri, P. and Quinet, P. (2021) Photoionization Models for High-density Gas. Astrophysical Journal, 908 (1). Art. No. 94. ISSN 1538-4357. doi:10.3847/1538-4357/abccd6.

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Relativistically broadened and redshifted 6.4–6.9 keV iron K lines are observed from many accretion powered objects, including X-ray binaries and active galactic nuclei. The existence of gas close to the central engine implies large radiation intensities and correspondingly large gas densities if the gas is to remain partially ionized. Simple estimates indicate that high gas densities are needed to allow for the survival of iron against ionization. These are high enough that rates for many atomic processes are affected by mechanisms related to interactions with nearby ions and electrons. Radiation intensities are high enough that stimulated processes can be important. Most models currently in use for interpreting relativistic lines use atomic rate coefficients designed for use at low densities and neglect stimulated processes. In our work so far we have presented atomic structure calculations with the goal of providing physically appropriate models at densities consistent with line-emitting gas near compact objects. In this paper we apply these rates to photoionization calculations, and produce ionization balance curves and X-ray emissivities and opacities that are appropriate for high densities and high radiation intensities. The final step in our program will be presented in a subsequent paper in which model atmosphere calculations will incorporate these rates into synthetic spectra.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kallman, T.0000-0002-5779-6906
Bautista, M.0000-0001-6837-3055
Deprince, J.0000-0002-3409-8232
García, J. A.0000-0003-3828-2448
Mendoza, C.0000-0002-2854-4806
Ogorzalek, A.0000-0003-4504-2557
Palmeri, P.0000-0002-4372-6798
Quinet, P.0000-0002-3937-2640
Additional Information:© 2021 The American Astronomical Society. Received 2020 August 5; revised 2020 November 9; accepted 2020 November 20; published 2021 February 16. Partial support for this work was provided by grant 80NSSC17K0345 through the NASA APRA program. J.A.G. acknowledges support from NASA ADAP grant 80NSSC19K0586, and from the Alexander von Humboldt Foundation. J.D. is a Research Fellow of the Belgian Fund for Research Training in Industry and Agriculture (FRIA), while P.P. and P.Q. are, respectively, Research Associate and Research Director of the Belgian Fund for Scientific Research (F.R.S.-FNRS). A.O. is supported by NASA under award number 80GSFC17M0002. We are very grateful to the referee for several constructive suggestions.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Alexander von Humboldt FoundationUNSPECIFIED
Fonds pour la Formation à la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium)UNSPECIFIED
Fonds de la Recherche Scientifique (FNRS)UNSPECIFIED
Subject Keywords:X-ray astronomy ; Atomic physics ; X-ray observatories ; Atomic spectroscopy
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: X-ray astronomy (1810); Atomic physics (2063); X-ray observatories (1819); Atomic spectroscopy (2099)
Record Number:CaltechAUTHORS:20210217-152552788
Persistent URL:
Official Citation:T. Kallman et al 2021 ApJ 908 94
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108098
Deposited By: Tony Diaz
Deposited On:18 Feb 2021 17:22
Last Modified:16 Nov 2021 19:08

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