Cool Stars 14 - Submitted Abstract # 181
This version created on 05 October 2006

The recombining flaring plasma of EV Lac


Urmila Mitra-Kraev, University of Sheffield, UK
Jan-Uwe Ness, Arizona State University, USA

We present the pure flaring spectrum of the active M-type star EV Lac,
as observed by the Chandra observatory in the X-ray range 1.8--26
Angstroms.  While, as expected, the flaring spectrum is dominated by
hotter lines than the quiescent one, we also find that certain line
ratios of the flaring spectrum are incompatible with a "coronal"
plasma in thermal equilibrium.  However, they are consistent with a
highly ionized, rapidly cooling plasma.  These findings have major
consequences for interpreting the plasma of active stellar coronae.
In particular, such thermal non-equilibrium conditions lead to a
suppression of the resonance line of O VII and affects the G-ratio,
which is often used for temperature diagnostics in collisionally
ionized plasma in thermal equilibrium.  Inconsistencies between the
temperature derived from the G-ratio and temperatures derived by other
means can thus be solved, as the flaring plasma is no longer in
thermal equilibrium.  We also find hugely enhanced densities in the
flaring plasma.

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