Session 33 - Gamma-ray Burst Counterparts and Afterglows.
Topical, Oral session, Tuesday, June 09
Friars,

## [33.10] Optical, IR, and Radio Follow-Up Studies of GRBs

S. G. Djorgovski, S. R. Kulkarni (Caltech), D. A. Frail (NRAO), J. S. Bloom, S. C. Odewahn, P. Shopbell, K. L. Adelberger, R. R. Gal, D. Vakil, A. N. Ramaprakash (Caltech), R. Goodrich (WMKO)

We will describe the studies of GRB afterglows done by the Caltech group. Some of the results to date include:

\star Establishment of the extragalactic nature of GRBs.

\star Detection of at least 3 host galaxies of GRBs and measurement of their redshifts.

\star Detection of the radio afterglow of a GRB.

\star Determination of physical parameters of fireballs for GRB afterglows.

\star Evidence for a significant range in the electromagnetic energy release in GRBs, reaching up to a few \times 10^53 erg (isotropic).

\star Evidence for a large range (up to a few hundred) in observed optical to x-ray (or \gamma-ray) flux ratios for GRB afterglows.

\star Evidence for dust extinction in at least one GRB afterglow.