Astron. Astrophys. Suppl. Ser. 138, 537-538
R. Sari1 and T. Piran 2
1 - Theoretical Astrophysics, California Institute of Technology, Pasadena, CA 91125, U.S.A.
2 - Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel , and Department of Physics, Columbia University, New York, NY 10027, U.S.A.
Received December 29; accepted December 29, 1998
We calculate the expected spectrum and light curves of the early afterglow. For short
GRBs the peak of the afterglow will be delayed, typically, by few dozens of seconds
after the burst. The X-ray and -ray characteristics of this delayed emission
provide a way to discriminate between late internal shocks emission (part of the GRB)
and the early afterglow signal. Detection of this delayed emission will prove the
internal shock scenario as producing the GRB, and will pinpoint the initial Lorentz
factor . In the optical band, the dominant emission arises from the reverse
shock. This shock, carries a comparable amount of energy to the forward shock. It
radiates this energy at much lower frequencies, producing a short optical flash of 15th
magnitude or brighter.
Copyright The European Southern Observatory (ESO)