Lithium Production in Companions of Accreting X-Ray Binaries by Neutron Spallation of C,N,O Elements

We examine the processes which could lead to the observed enhancement of Li and possibly other light elements (Be, B) in the companions of a number of X-ray novae. We conclude that one of the most promising mechanisms is the spallation of CNO elements on the surface of the companion induced by the neutron flux produced in the hot accretion flow onto the compact object. Direct production of the observed Li and its deposition onto the dwarf companion seem less likely, mainly because of the possibility of its destruction in the production region itself and difficulties in its deposition associated with the configuration of the companion's magnetic field. We discuss other potential observables of the above scenario.Comment: 23 pages Latex, of which 5 pages of tables, to appear in the Astrophysical Journal, Vol 512, Feb 10 issu