X-Ray Spectroscopy in the Microcalorimeter Era 4: Optical Depth Effects on the Soft X-Rays Studied with Cloudy

Priyanka Chakraborty, Gary J. Ferland, Marios Chatzikos, Andrew C. Fabian, Stefano Bianchi, Francisco Guzmán, Yuanyuan Su

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


In this paper, we discuss atomic processes modifying the soft X-ray spectra from optical depth effects like photoelectric absorption and electron scattering suppressing the soft X-ray lines. We also show the enhancement in soft X-ray line intensities in a photoionized environment via continuum pumping. We quantify the suppression/enhancement by introducing a "line modification factor (f mod)."If 0 ≤ f mod ≤ 1, the line is suppressed, which could be the case in both collisionally ionized and photoionized systems. If f mod ≥ 1, the line is enhanced, which occurs in photoionized systems. Hybrid astrophysical sources are also very common, where the environment is partly photoionized and partly collisionally ionized. Such a system is V1223 Sgr, an Intermediate Polar binary. We show the application of our theory by fitting the first-order Chandra Medium Energy Grating (MEG) spectrum of V1223 Sgr with a combination of Cloudy-simulated additive cooling-flow and photoionized models. In particular, we account for the excess flux for O vii, O viii, Ne ix, Ne x, and Mg xi lines in the spectrum found in a recent study, which could not be explained with an absorbed cooling-flow model.

Original languageEnglish
Article number70
JournalAstrophysical Journal
Issue number2
StatePublished - Aug 1 2022

Bibliographical note

Funding Information:
We acknowledge support by NSF (1816537, 1910687), NASA (17-ATP17-0141, 19-ATP19-0188), and STScI (HST-AR-15018). M.C. also acknowledges support from STScI (HST-AR-14556.001-A). S.B. acknowledges financial support from the Italian Space Agency (grant 2017-12-H.0) and from the PRIN MIUR project black hole winds and the BaryonLife Cycle of Galaxies: the stone-guest at the galaxy evolution supper, contract 2017-PH3WAT.

Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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