2003/04/03 by Christopher W. Mauche, Duane A. Liedahl, Kevin B. Fournier · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Solar and Space Plasma Dynamics #astro-ph
paper · pdf · doi:10.1086/375684
11 pages including 3 encapsulated postscript figures; LaTeX format, uses aastex.cls; accepted on 2003 April 3 for publication in The Astrophysical Journal
arxiv created 2003/04/03 · openalex publication_date 2003/04/11 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
Using the Livermore X-ray Spectral Synthesizer, which calculates spectral models of highly charged ions based primarily on HULLAC atomic data, we investigate the temperature, density, and photoexcitation dependence of the I (11.92 Å)/ I (11.77 Å) line ratio of Fe XXII. We find that this line ratio has a critical density n c ≈ 5 × 10 13 cm -3 , is approximately 0.3 at low densities and 1.5 at high densities, and is very insensitive to temperature and photoexcitation; therefore, it is a useful density diagnostic for sources like magnetic cataclysmic variables, in which the plasma densities are high and in which the efficacy of the He-like ion density diagnostic is compromised by the presence of a bright ultraviolet continuum. Applying this diagnostic to the Chandra High Energy Transmission Grating spectrum of the intermediate polar EX Hya, we find that the electron density of its T e ≈ 12 MK plasma is n e = 1.0 × 10 14 cm -3 , which is orders of magnitude greater than that typically observed in the Sun or other late-type stars.