Detection and high-resolution spectroscopy of a huge flare on the old M 9 dwarf DENIS 104814.7-395606.1

We report a flare on the M 9 dwarf DENIS 104814.7-395606.1, whose mass places it directly at the hydrogen burning limit. The event was observed in a spectral sequence during 1.3 h. Line shifts to bluer wavelengths were detected in , , and in the Na i D lines, indicating mass motions. In addition we detect a flux enhancement on the blue side of the two Balmer lines in the last spectrum of our series. We interpret this as rising gas cloud with a projected velocity of about 100 which may lead to mass ejection. The higher Balmer lines to are not seen due to our instrumental setup, but in the last spectrum there is strong evidence for being in emission.