On the observability of optically thin coronal hyperfine structure lines

M. Chatzikos, G. J. Ferland, R. J.R. Williams, A. C. Fabian

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


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 57Fe 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.

Original languageEnglish
Article number96
JournalAstrophysical Journal
Issue number2
StatePublished - Jun 1 2014


  • clusters
  • formation - methods
  • galaxies
  • general
  • individual (NGC 1275, M87) - ISM
  • individual (Perseus, Virgo) - galaxies
  • individual objects (Extended Orion Nebula) - line
  • numerical - radio lines

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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