Simulations of AR Lac & II Peg

TITLE: HETGS Observations of the Eclipsing Binary AR Lac.

TITLE: HETGS Observations of the Single-lined Binary II Peg.

Coronal sources, such as the RS CVn binaries, will be studied extensively with the HETGS. The emission lines will provide information on the temperature, density, geometric, and temporal structures of stellar corona, and provide crucial information relating to the underlying heating mechanisms. Two RS CVn stars will be observed as part of the HETGS GTO:

AR Lac is an eclipsing binary. It will be observed through primary eclipse to map the extent of the emitting structures on the primary star. It will also be observed at quadratures to determine the relative contributions from each stellar component.

II Peg is a single-lined binary. It is very active, and is known to flare frequently. It's spectrum will be studied for temporal variability due to flaring, as well as for temperature structure.

Figure 1 : A simulation of AR Lac-like corona for 34 ks. The counts spectrum was made by binning both plus and minus first order photons in the MEG region into 0.012 mm bins, after applying an 0.32 arcsec aspect reconstruction uncertainty to the positions. The bin size is smaller than an {\sc acis} pixel, in anticipation of oversampling achieved by the aspect dither. The input model was a continuous emission measure distribution peaking near $\log T=7$ with flux of $4\times10^{-11} ergs cm^{-2} s^{-1}$. Effects of broadening are demonstrated in the inset.

Figure 2 shows the sigma from a Gaussian fit to the count-profiles. Results for two lines are shown for no-broadening, just thermal, and thermal plus microturbulence. O VIII is resolved even for conservative estimates of the resolution, for a 40ks observation. The strong lines near 12 Å will have twice the MEG dispersion in the HEG spectrum, and will also be well resolved.

More to come...soon....

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