Cool Stars 14 - Submitted Abstract # 55 This version created on 05 October 2006 Near-Ultraviolet Spectroscopy of Flares on YZ CMi Suzanne Hawley, University of Washington Lucianne Walkowicz, University of Washington Joel Allred, Drexel University Jeff Valenti, Space Telescope Science Institute Near-ultraviolet spectroscopic data obtained with the HST STIS instrument on the dMe flare star YZ Canis Minoris (YZ CMi) were analyzed. Flare and quiet intervals were identified from the broadband near-UV light curve, and the spectrum ofeach flare was separately extracted. Mg II and Fe II line profiles show similar behavior during the flares. Two large flares allowed time-resolved spectra tobe analyzed, revealing a very broad component to the Mg II k line profile in atleast one flare spectrum (F9b). If interpreted as a velocity, this component requires chromospheric material to be moving at about 260 km/sec, implying kinetic energy far in excess of the radiative energy. The Mg II k flare line profileswere compared to recent radiative hydrodynamic models of flare atmospheres undergoing electron beam heating. The models successfully predict red enhancements in the line profile with typical velocity of a few km/sec, but do not reproduce the flares showing blue enhancements, or the strongly broadened line observed inflare F9b. A more complete calculation of redistribution into the line wings, including the effect of collisions with the electron beam, may resolve the origin of the excess line broadening. ----------------------------------