SIMBAD references

If the efficiency for producing gamma rays is the same in short-duration (≲2 s) gamma-ray bursts (GRBs) as in long-duration GRBs, then the average kinetic energy per solid angle in short GRBs must be ∼20 times less than that of long GRBs. Assuming that the relativistic shocks in short- and long-GRB afterglows have similar parameters, we show that the afterglows of short GRBs will be, on average, 10-40 times dimmer than those of long GRBs. We find that the afterglow of a typical short GRB will be below the detection limit (≲30 µJy) of searches at radio frequencies. The afterglow would also be difficult to observe in the optical, where we predict R≳23 10 hr after the burst. The radio and optical afterglows would be even fainter if short GRBs occurred in a low-density medium, as expected in neutron star-neutron star and neutron star-black hole merger models. Early (≲1 day) observations in X-rays offer the best prospects for detecting short-GRB afterglows.