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arXiv · astro-ph/0204141

The Broadband Afterglow of GRB980329

S. A. Yost·D. A. Frail·F. A. Harrison·R. Sari·D. Reichart·J. S. Bloom·S. R. Kulkarni·G. H. Moriarty-Schieven·S. G. Djorgovski·P. A. Price·R. W. Goodrich·J. E. Larkin·F. Walter·D. S. Shepherd·D. W. Fox·G. B. Taylor·E. Berger·T. J. Galama
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Abstract

We present radio observations of the afterglow of the bright gamma-ray burst GRB980329 made between one month and several years after the burst, a re-analysis of previously published submillimeter data, and late-time optical and near-infrared (NIR) observations of the host galaxy. From the absence of a spectral break in the optical/NIR colors of the host galaxy, we exclude the earlier suggestion that GRB980329 lies at a redshift of z >~5. We combine our data with the numerous multi-wavelength observations of the early afterglow, fit a comprehensive afterglow model to the entire broadband dataset, and derive fundamental physical parameters of the blast-wave and its host environment. Models for which the ejecta expand isotropically require both a high circumburst density and extreme radiative losses from the shock. No low density model (n << 10 cm^{-3}) fits the data. A burst with a total energy of ~ 10^{51} erg, with the ejecta narrowly collimated to an opening angle of a few degrees, driven into a surrounding medium with density ~ 20 cm^{-3}, provides a satisfactory fit to the lightcurves over a range of redshifts.

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S. A. Yost, D. A. Frail, F. A. Harrison, R. Sari, D. Reichart, J. S. Bloom, S. R. Kulkarni, G. H. Moriarty-Schieven, S. G. Djorgovski, P. A. Price, R. W. Goodrich, J. E. Larkin, F. Walter, D. S. Shepherd, D. W. Fox, G. B. Taylor, E. Berger, T. J. Galama. 2002-06-03. The Broadband Afterglow of GRB980329. https://doi.org/10.1086/342175

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