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Title: K-SHELL PHOTOABSORPTION OF MAGNESIUM IONS

X-ray photoabsorption cross sections have been computed for all magnesium ions with three or more electrons using the R-matrix method. A comparison with other available data for Mg II-Mg X shows good qualitative agreement in the resultant resonance shapes. However, for the lower ionization stages, and for singly ionized Mg II in particular, the previous R-matrix results overestimate the K-edge position due to the neglect of important orbital relaxation effects, and a global shift downward in photon energy of those cross sections is therefore warranted. We have found that the cross sections for Mg I and Mg II are further complicated by the M-shell (n = 3) occupancy. As a result, the treatment of spectator Auger decay of 1s → np resonances using a method based on multichannel quantum defect theory and an optical potential becomes problematic, making it necessary to implement an alternative, approximate treatment of Auger decay for neutral Mg I. The new cross sections are used to fit the Mg K edge in XMM-Newton spectra of the low-mass X-ray binary GS 1826-238, where most of the interstellar Mg is found to be in ionized form.
Authors:
 [1] ;  [2] ; ;  [3] ;  [4] ;  [5] ;  [6]
  1. Department of Computer Engineering, Hasan Kalyoncu University, 27100 Sahinbey, Gaziantep (Turkey)
  2. Department of Physics, Auburn University, Auburn, AL 36849 (United States)
  3. Centro de Física, Instituto Venezolano de Investigaciones Científicas, Caracas 1020 (Venezuela, Bolivarian Republic of)
  4. Harvard-Smithsonian Center for Astrophysics, MS-6, 60 Garden Street, Cambridge, MA 02138 (United States)
  5. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  6. Department of Physics, Western Michigan University, Kalamazoo, MI 49008-5252 (United States)
Publication Date:
OSTI Identifier:
22340168
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 214; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CROSS SECTIONS; ELECTRONS; K SHELL; M SHELL; MAGNESIUM IONS; PHOTONS; QUANTUM MECHANICS; R MATRIX; RELAXATION; RESONANCE; SPECTRA; X RADIATION