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J.L. Linsky (JILA), M. Gagne (West Chester Univ.)
The early-K dwarf AB Dor is a nearby (15 pc), young (20--30 Myr), rapidly rotating (Prot = 0.514 day) star with saturated X-ray emission (Lx/Lbol ~10-3) and cool prominence-like gas extending several stellar radii into its corona. We observed this extensively studied star on 1999 Oct 9 for 60 ks with the high energy transmission grating (HETG/ACIS-S) on Chandra. The rich X-ray spectra contain emission lines of N, O, Ne, Mg, Al, Si, S, Ar, Ca, Fe, and Ni. As is seen in other active stars, the Ne abundance is high and the Fe abundance low compared to solar photospheric abundances, indicating the reverse of the enhanced first ionization potential (FIP) effect seen in the solar corona. The emission measure distribution shows peaks near \log T = 6.8 and 7.3, and the helium-like triplets of O~VII, Ne~IX, and Mg~XI indicate electron densities \log ne ~11.0. We will use these data to infer the size and properties of coronal loops in the stellar corona. We find no noticeable line shifts indicative of a wind or downflows.
This GTO Chandra program is supported by NASA through a grant to NIST and the University of Colorado.