The Effect of Nonthermal Protons on the High-Energy Spectra of Black Hole Binaries

In the inner regions of an accretion disk around a black hole, the presence of nonthermal protons via p-p collisions would produce electrons, positrons, and γ-rays. For such a scenario, the steady state electron-positron distribution is computed taking into account Compton cooling, e-e+ pair production (due to γ-γ interactions), and pair annihilation. The resultant spectra have a broad feature around 1-10 MeV, which may be tested with observations by the International Gamma-Ray Astrophysical Laboratory and the Gamma-Ray Large Area Space Telescope. Using the available OSSE data for the black hole system GRS 1915+115, we illustrate that an upper limit on the nonthermal proton fraction can be obtained, which may put constraints on the acceleration process active in this system.