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Session 81 - Variable Cool and Late Type Stars.
Display session, Wednesday, January 15
Metropolitan Ballroom,

[81.09] Chromospheric Line Blanketing and the Hydrogen Spectrum of dM Stars

C. I. Short, J. G. Doyle (Armagh Obs.)

We present non-LTE calculations of the H\,\sc i spectrum in a grid of chromospheric models that represents a dM0 star in which the activity level ranges from quiescent to very active. We investigate three different treatments of the background opacity: 1) continuous opacity only, 2) blanketing due to lines that form in the photosphere below T_\mboxmin, and 3) blanketing by lines that form throughout the entire outer atmosphere. We show that the predicted W_\lambda of Ly\alpha in all models, and of H\alpha in very active (dMe) stars, is reduced by as much as a factor of \approx 4 by the inclusion of background line opacity. A consistent treatment of line blanketing that includes the effect of the chromospheric and transition region temperature structure in the calculation of background line opacity is necessary for the accurate calculation of Ly\alpha, and in some cases H\alpha, in thes e stars. The H\alpha line in less active models, and the Pa\beta line in all models, is negligibly affected by the treatment of background opacity. We also show that the broad-band continuum flux in regions where \lambda < 2000 A is increased by as much as a factor of \approx 3 in some models by the inclusion of chromospheric line blanketing.

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Program listing for Wednesday