ENERGY IMPLICATIONS OF LI PRODUCTION IN X-RAY TRANSIENTS

The Li-abundances recently observed in the low mass secondaries of sev eral soft X-ray transients have been proposed to come from nuclear rea ctions in the vicinity of the compact objects during the outbursts of these systems. This scenario implies a large flux of energetic particl es in X-ray transients. We show that Li newly produced in an outburst is mixed into the secondary very quickly, so that the observed abundan ce must represent the average production over many outbursts. With kno wn Limits on the Li-depletion rates in low mass stars, we derive minim al energy fluxes in energetic protons and/or alpha-particles, assuming that either the secondary or the accretion disk is the main target of this flux. In both cases, at least a few per cent of the accretion en ergy must be converted to fast particles with energies exceeding 10 Me V/nucleon.