Jg. Skibo et al., COMPTON-SCATTERING IN JETS - A MECHANISM FOR SIMILAR-TO-0.4 AND LESS-THAN-OR-EQUAL-TO-0.2 MEV LINE PRODUCTION, The Astrophysical journal, 431(1), 1994, pp. 120000039-120000042
We show that gamma-ray line emission at approximately 0.4 and less tha
n or similar to 0.2 MeV can be produced by Compton scattering of beame
d radiation in the jets of Galactic black hole candidates. This mechan
ism has the novel feature of not invoking the presence of e+-e- pairs.
To produce the two lines, we employ a symmetric double-sided jet with
bulk flow velocity of about 0.5c and incident beam radiation with a h
ard energy spectrum. We show that the two lines can be seen at viewing
-angle cosines relative to the jet ranging from 0.2 to 0.6. This compr
ises 40% of the total solid angle. In addition, the line radiation is
approximately 10% polarized. Depending on the bulk flow and viewing an
gle, the model can produce lines at other energies as well. In particu
lar, a broad feature near 1 MeV can be seen by viewing the jet close t
o its axis. Our model can also accommodate single-line spectra if the
beamed gamma-ray emission or the jets themselves are asymmetric.