Cool Stars 14 - Submitted Abstract # 199
This version created on 05 October 2006

Stellar coronae in saturated and supersaturated late-type stars.


David Garcia-Alvarez, Imperial College London
David Garcia-Alvarez, Harvard-Smithsonian CfA 
Jeremy Drake, Harvard-Smithsonian CfA 
Vinay Kashyap, Harvard-Smithsonian CfA 
LiWei Lin, Harvard-Smithsonian CfA

AB Dor, Speedy Mic, and Rst 137B are fast-rotating (Porb<12hr), young
(~30Myr) late-type stars.  An analysis of their coronal properties
yields illuminating glimpses of the fundamental differences in
magnetic dynamos and activity between these stars and those in
"slower" rotators (log(Rossby number)>-1.5).  We compare our results
with those in the literature for such slower rotators and find
numerous contrasting features and trends:  
   (1) the relative emission at high-temperature rises inversely
   with the Rossby number until the boundary of the
   saturated/supersaturated regimes, and then the trend reverses
   for supersaturated stars;  
   (2) the absolute Fe coronal abundances decrease with Rossby
   number;  there are also suggestions of a possible mass
   dependency for the chemical fractionation (such as
   gravitational settling of the heavier Fe ions);  
   (3) the O/Fe ratio increases as stars approach
   supersaturation, and then appears to decrease once
   supersaturation is achieved;  
   (4) binary systems with subgiant components generally show
   smaller O/Fe values compared to dwarfs;  and 
   (5) the Ne/Fe ratio shows a similar trend with Rossby number
   as that of O/Fe.  
We discuss the coronal thermal structure and chemical
composition of satutared-supersaturated stars in the context of
currently favored ideas of coronal stripping and dynamo
saturation in rapidly rotating stars.

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