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Title: On the observability of optically thin coronal hyperfine structure lines

We present CLOUDY calculations for the intensity of coronal hyperfine lines in various environments. We model indirect collisional and radiative transitions, and quantify the collisionally excited line emissivity in the density-temperature phase space. As an observational aid, we also express the emissivity in units of that in the 0.4-0.7 keV band. For most hyperfine lines, knowledge of the X-ray surface brightness and the plasma temperature is sufficient for rough estimates. We find that the radiation fields of both Perseus A and Virgo A can enhance the populations of highly ionized species within 1 kpc. They can also enhance line emissivity within the cluster core. This could have implications for the interpretation of spectra around bright active galactic nuclei. We find the intensity of the {sup 57}Fe XXIV λ3.068 mm line to be about two orders of magnitude fainter than previously thought, at ∼20 μK. Comparably bright lines may be found in the infrared. Finally, we find the intensity of hyperfine lines in the Extended Orion Nebula to be low, due to the shallow sightline. Observations of coronal hyperfine lines will likely be feasible with the next generation of radio and submillimeter telescopes.
Authors:
;  [1] ;  [2] ;  [3]
  1. University of Kentucky, Lexington, KY 40506 (United States)
  2. AWE plc, Aldermaston, Reading RG7 4PR (United Kingdom)
  3. Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)
Publication Date:
OSTI Identifier:
22356801
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 787; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BRIGHTNESS; ELECTRON TEMPERATURE; EMISSIVITY; GALAXY CLUSTERS; GALAXY NUCLEI; HYPERFINE STRUCTURE; ION TEMPERATURE; IRON 57; KEV RANGE; NEBULAE; PHASE SPACE; SURFACES; TELESCOPES; X RADIATION