Indirect manifestation of GRBs in the Galaxy: Compton trails and positrons

Two independent indirect manifestations of Galactic gamma-ray bursts (GRBs) are considered, whose importance for gamma-ray astronomy will depend on a still poorly known -- though astrophysically important -- parameter, namely the GRB repetition timescale in a Galaxy like ours. Both phenomena are expected to lead to observational constrains about this timescale. The first one relates to the Compton scattering of the GRB gamma-rays in the disk of the Galaxy, and the second one to the long-term annihilation pattern of positrons produced just ahead of the ultra-relativistic plasma, by photo-pair production.Comment: 4 pages, 2 figures (uses vietnam.sty). To appear in the proceedings of the 5th Rencontres du Vietnam, "New Views on the Universe", Hanoi, Aug 5-11, 200