Neutrino-induced production of isotope 11B in the carbon layer of a star

Neutrinos emitted by a collapsing stellar core are shown to interact effectively with the carbon layer of the stellar envelope, thereby producing a sufficiently large amount of isotope 11B to account for the cosmic abundance observed. Since the mechanism of stellar envelope expulsion which accompanies the gravitational collapse of the core has not yet been developed in detail, the temperature conditions of the expelled envelope are not quite clear. Hence, the net yield of isotope 11B, relative to carbon - as shown in the present work - ranges from 5 x 10-6 to 5 x 10-4 (the observed cosmic value of this ratio is (2.5-5) x 10-7). The upper limit of the above range of calculated values refers to the case when the neutrino-induced isotope 11B burns via thermonuclear reactions due to the carbon layer heated by the neutrino emission itself. The lower limit, however, was obtained within the model assuming a considerably higher temperature of matter which results from the condition of hydrostatic equilibrium. (orig.)