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We report on a new and unexpected impulsive phenomenon during two stellar flares simultaneously observed in soft X-rays by the ROSAT Observatory and using ground-based, high-speed optical photometry at the Wendelstein Observatory in Bavaria, Germany. SXR bursts follow the $U-$ and $B-$band events by approximately 30 s. We concentrate on the correlation of the optical and initial SXR bursts. Statistical analysis verifies the significance of these events. They may offer an unexpected window on the impulsive phase of stellar flares. This would be especially timely since the ASCA Observatory has just begun its mission and should be capable of observing stellar flares in some detail. While the precise physical implications of our observations remain unclear, we argue that our data show the signature of X-ray emission from the impulsive phase of a stellar flare rather than that of a microflare or a compact loop flare. The curious time relationship between the optical and SXR bursts may lend support to a gas-dynamic model proposed by Katsova and Livshits.
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