3.
High-velocity evaporation during a flare on AT Mic.
Gunn A.G., Doyle J.G., Mathioudakis M., Houdebine E.R. &
Avgoloupis S.,
A & A, 1994, 285, 489.
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ABSTRACT. We present and discuss observations of a flare event
on the dM4.5e star AT Mic (Gl 799AB). These data show evidence of an
energetic flare with a radiated energy of 3 10^31 erg in the
range 3600-4200 Angstroms. The Balmer emission lines display a prominent blue
asymmetry which has been used to constrain the velocity of the
associated bulk plasma motion. Simple models were applied to derive
order of magnitude estimates for the mass and kinetic energy budget
of the flare for assumed electron density, ionization fraction and
temperature values. It is found that the kinetic energy of the flare
plasma is two orders of magnitude less than the radiative energy
release.
The chromospheric Ca II H & K lines are also observed to have a
blue-shifted component which has not been observed prior to these
results. We suggest that this is evidence of a very energetic particle
beam penetrating to the cooler atmospheric layers where Ca II H & K
is formed.
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