Ion‐by‐Ion Differential Emission Measure Determination of Collisionally Ionized Plasma. II. Application to Hot Stars

Abstract

In a previous paper we have described 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. We apply this technique to the Chandra HETGS spectra of all of the nine hot stars available to us at the time that this project was initiated. We find that DEM distributions of six of the seven O stars in our sample are very similar, but that θ1 Ori C has an X-ray spectrum characterized by higher temperatures. The DEM distributions of both of the B stars in our sample have lower magnitudes than those of the O stars, and one, τ Sco, is characterized by higher temperatures than the other, β Cru. These results confirm previous work in which high temperatures have been found for θ1 Ori C and τ Sco and taken as evidence for channeling of the wind in magnetic fields, the existence of which is related to the stars' youth. Our results demonstrate the utility of our method for deriving temperature information for large samples of X-ray emission-line spectra.