Ion-by-ion Differential Emission Measure Determination of Collisionally Ionized Plasma. I. Method

We describe a technique to derive constraints on the differential emission measure (DEM) distribution, a measure of the temperature distribution, of collisionally ionized hot plasmas from their X-ray emission-line spectra. This technique involves fitting spectra using a number of components, each of which is the entire X-ray emission-line spectrum for a single ion. It is applicable to high-resolution X-ray spectra of any collisionally ionized plasma, and it is particularly useful for spectra in which the emission lines are broadened and blended, such as those of the winds of hot stars. This method does not require that any explicit assumptions about the form of the DEM distribution be made and is easily automated. Subject headinggs: plasmas — radiative transfer — X-rays: general