0220140

Magnetically active stars are among the most ubiquitous high-energy sources in the observable skyyet they have been studied predominantly in the soft X-ray range below 10 keV where thermalcoronal plasma is the predominant source of photons. However both solar analogy and the signaturesof non-thermal radio and optical impulsive bursts from active stellar sources suggest the presence of a largepopulation of non-thermal electrons out to MeV energies. They are expected to produce a strong non-thermalbremsstrahlung continuum above 10-20 keV. We propose a novel investigation to search for non-thermalhard X-ray emission in stellar sources by simultaneously using the JEM-X (for soft X-rays) the IBIS/ISGRI(for non-thermal emission) and the OM instruments (for optical electron-induced bursts). Simultaneous radioobservations will detect enhanced production of non-thermal electron populations. Timing studiesbetween the different (thermal/non-thermal) components will indicate the nature of the hard X-rays.The results will be important to assess the role of accelerated particles in the primary energy releasein stellar coronae as well as their role in coronal heating. [truncated! Please see actual data for full text]