A coordinated search for flares from the dMe star YZ Canis Minoris was performed in 1979 October using the Einstein Observatory and ground-based optical and radio telescopes. An event was detected in the optical, radio, and X-ray wavebands on October 25, and a second optical event on October 27 was seen as a marginal (2

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Six flares of the dMe star YZ CMi have been observed with simultaneous photometry and high-dispersion, time-resolved spectroscopy. The spectra have temporal resolutions of 3 minutes with spectral resolutions of 0.24 Â. The largest observed flare had a U band amplitude of 1.5 mag. Ha and Hß line profiles did not broaden during any of the observed flares, although the line center intensity increased by over a factor of 2 during some flares. After the initial increase in intensity, the emission line strength decreases but remains at enhanced levels for hours following U band flares. The Ha flare luminosity and total energy are compared to corresponding properties of solar flares.

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High-resolution red (5300-7300 Â) spectra of the flare star AD Leonis were obtained with the Kitt Peak 4 m echelle spectrograph system at a spectral resolution of 0.22 Â at Ha. A series of time-trailed plates with 5 hours integration in total were averaged together to obtain a representation of the star's nonflaring spectrum with high signal-to-noise ratio. The He i A5876 triplet line and À6678 singlet line appear in emission with measured equivalent widths of 0.312 ± 0.016 Â and 0.058 ± 0.029 Â, respectively. The corresponding triplet-to-singlet line flux ratio is 3.7, close to the ratio of the level statistical weights. We argue that the He i lines are not produced by recombination and cascade following photoionization by À < 504 Â coronal photons, but are instead collisionally excited. We suggest that these lines are formed in a geometrically thin chromospheric layer at 20,000-50,000 K with a column density of n e l x 6 x 10 18 cm" 2. The sodium D emission lines (À5890, A5896) are found to be stellar in origin, with measured FWHM of 0.7 Â for both lines, and the Ha line has a FWHM of 1.4 Â. No other chromospheric emission lines were found in this spectral region.