POSTER PAPER 8.04
X-ray Spectra and Light Curves of AR Lac: Temperature Structure, Abundances, and Variability.
David Huenemoerder, Claude Canizares, Kevin Tibbetts
Institute:Massachusetts Institute of Technology
Contact Email: dph@space.mit.edu
Abstract:
We observed AR Lac, an eclipsing RS CVn binary star, with the Chandra
High Energy Grating Spectrometer for a total of 100 ks divided into
six intervals covering both quadratures and eclipses. We repeated
observations at each phase. At least two flares were seen, in which
the flux increased by factors of two and four. The flares occurred
near eclipse phases and compromised detection of eclipse modulation.
The quadrature fluxes were the most stable, but they also show
non-repeating trends. Quadrature line profiles are broadened relative
to eclipse profiles, presumably due to orbital velocity Doppler
shifted emission from each binary component. The spectrum appears to
be iron poor and neon rich, similar to HR 1099, but not as extreme as
II Pegasi. We will examine line strengths, widths, and positions
vs. phase, and present preliminary differential emission measure
models and abundance determinations using the APED emissivity
database.
This work is supported by NASA contract NAS8-38249 (HETG) and SAO
SV1-61010 (CXC) to MIT.
Index Keywords: AR Lac; Chandra; Spectra, X-ray
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Manuscript submitted: 2001-Sep-05
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown,
G. M. Harper, & T. R. Ayres.
Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.