Buzasi, Derek L.

Contact Email: derek.buzasi@usafa.af.mil
Institute: USAFA
First Coauthor: David P. Huenemoerder
Institute: MIT
Second Coauthor: Heather L. Preston
Institute: USAFA
Subject Area: Stellar Atmospheres, Circumstellar Material
Waveband: X-rays
Technique: Spectroscopy
Presentation: Poster Display
Title: After the Flare: The Perplexing X-Ray Spectrum of FK Com
Abstract: FK Com, whose peculiarities were first noted by Merrill (1948), is a single G-type giant rotating near the breakup velocity (v sin i = 162.5 km/s; see Huenemoerder et al. 1993). The angular momentum derived from this rapid rotation, which corresponds to a period of 2.4 days (Chugainov 1976), exceeds that possible for a main sequence progenitor, and the hypothesis has therefore been advanced that FK Com is in fact a recently coalesced binary (see, e.g. Ramsey et al. 1981, Huenemoerder et al. 1993). FK Com thus provides a unique laboratory in which to study the stellar dynamo under extreme conditions in a single star, independent of interactions (mass transfer, colliding winds, etc.) due to a binary companion. We observed FK Com for 40 kiloseconds during March 2000 using the Chandra ACIS-S/HETG. The spectrum is dominated by lines from highly ionized species of iron, such as Fe XXIV, XXV, and XXVI, indicating the presence of very high-temperature coronal material. Line and continuum intensities were variable during the observation, with the dominant change being a monotonic decay which we interpret as the aftereffects of a flare. An interesting feature of the spectrum is the small Fe XVII 15.2/Fe XVII 15.26 ratio, which has been claimed in the case of the solar corona to indicate high opacity. In this paper, we will discuss model fits to the spectrum, variability, and limits that can be placed on the column density to FK Com.