Ultraviolet radiation from stellar flares and the coronal X-ray emission for dwarf-Me stars

The origin of chromospheric and coronal emission is thought to derive ultimately from magnetic fields generated by a dynamo mechanism involving the interaction of rotation and convection¹. Although these magnetic fields are difficult to detect directly, the dramatic stellar flares, believed to be the result of magnetic reconnection, have been observed for many years on dwarf Me (dMe) stars. Here we correlate Einstein observations of the X-ray flux of quiescent dMe stars with the time-averaged energy emitted by flares in the Johnson-U band, showing that the X-ray energy emitted by the coronae of these stars is about an order of magnitude greater than the U-band flare energy. From our estimate of the ratio of the total radiation emitted to the U-band flux, it is possible that, if a similar amount of energy were dissipated in the stellar atmosphere, then the observed flare events could heat the coronae of these stars.