PI: Mihalis Mathioudakis, Queens University of Belfast, M.Mathioudakis@qub.ac.uk
Address: Belfast BT7 1NN, Northern Ireland
CoI: Damian Christian, John Hopkins University
Title: A search for supersaturation in stellar chromospheres
Abstract: The rotation-activity relations of late-type stars exhibit the effects of saturation in the chromospheric and coronal emission. Recent X-ray observations have shown that ultra fast rotators (vsini > 30 km sec^-1) show a decline in their coronal emission. This effect is called \em super-saturation. Theoretical models predict that as the increased rotational velocity decreases the apparent surface gravity, the hot coronal plasma becomes unstable and cools down to chromospheric temperatures. More cool loops emitting in chromospheric lines can exist but not in X-rays. We propose to observe the chromospheric lines of Ca II H&K and hydrogen Balmer, in a group of EUV/X-ray selected active late-type stars. The rotational periods of these objects are in excess of 10 km s^-1. The requested observations will allow us to test the model predictions.
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