Cool Stars 14 - Submitted Abstract # 151
This version created on 05 October 2006

The Spatial Structure of the Coronae of XY UMa in March 2005


Frederick M. Walter, Stony Brook University
Lisa Edelhaeuser, Julius-Maximilians-Universitaet Wuerzburg
Eric Stempels, St Andrews
David Latham, CfA
Scott J. Wolk, CfA

The detached partially-eclipsing XY UMa system is a member of the
short-period class of RS CVn binaries.  The G2V and K5V components
rotate synchronously with the 0.48 day binary period.  Eclipsing
systems are fundamentally important in astrophysics because eclipse
timing and modelling can yield the radii of, in this case, the stellar
coronae.  We report on a 25 hour XMM observation in March 2005 that
covered over 2 orbital periods.  We obtained simultaneous optical
photometry and contemporaneous high dispersion spectroscopy.  We used
the XMM EPIC and OM data to construct X-ray and UV light curves.  Both
primary and secondary eclipses are detected amidst the inherent
variability of an active stellar corona.  High-time-resolution B-band
photometry of primary eclipse from the Nordic Optical Telescope failed
to detect evidence of large dark regions on the primary.  High
resolution spectra give an improved orbital ephemeris.  We will
discuss the XMM light curves, and our best constraints on the shape
and location of the coronal gas in the system.

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