Relationships among the Intensities of LI-, BE-, and NA-like Resonance Lines in Collisionally Ionized Astrophysical Plasmas (10⁵<=T_e<=10⁷ K)

Abstract

The strongest lines emitted from optically thin collisionally ionized astrophysical plasmas are usually those of the Li-, Be-, and Na-like sequences. When numerous other weaker lines are also measurable in the spectrum, the derivation of relative element abundances is reasonably straightforward. However, for many sources only the strongest lines will be observed, so here we explore under what conditions it may be possible to determine relative element abundances in this case. We find that several temperature regions exist in which the ratios of these strong lines can be fairly insensitive to temperature. We discuss applications to solar/stellar coronae, the interstellar medium, and SN 1987A. Additionally under certain conditions in the solar corona ratios of Li-like line intensities to those of He II are found to allow relatively straightforward determinations of the He abundance.