Kavli Affiliate: Claude Canizares
| First 5 Authors: David Huenemoerder, Claude Canizares, Kevin Tibbetts, ,
| Summary:
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.
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