  The jet axes and the orbital planes of microquasar systems are usually
assumed to be approximately perpendicular, eventhough this is not currently an
observational requirement. On the contrary, in one of the few systems where the
relative orientations are well-constrained, V4641Sgr, the jet axis is known to
lie not more than ~36 degrees from the binary plane. Such a jet, lying close to
the binary plane, and traveling at a significant fraction of the speed of light
may periodically impact the secondary star initiating nuclear reactions on its
surface. The integrated yield of such nuclear reactions over the age of the
binary system (less the radiative mass loss) will detectably alter the
elemental abundances of the companion star. This scenario may explain the
anomalously high Li enhancements (roughly ~20-200 times the sun's photospheric
value; or, equivalently, 0.1-1 times the average solar system value) seen in
the companions of some black-hole X-ray binary systems. (Such enhancements are
puzzling since Li nuclei are exceedingly fragile - being easily destroyed in
the interiors of stars - and Li would be expected to be depleted rather than
enhanced there.) Gamma-ray line signatures of the proposed process could
include the 2.22 MeV neutron capture line as well as the 0.478 MeV 7Li*
de-excitation line, both of which may be discernable with the INTEGRAL
satellite if produced in an optically thin region during a large outburst. For
very energetic jets, a relatively narrow neutral pion gamma-decay signature at
67.5 MeV could also be measurable with the GLAST satellite. We argue that about
10-20% of all microquasar systems ought to be sufficiently misaligned as to be
undergoing the proposed jet-secondary impacts.
