The broadband afterglow of GRB 980703

D. A. Frail*, S. A. Yost, E. Berger, F. A. Harrison, R. Sari, S. R. Kulkarni, G. B. Taylor, J. S. Bloom, D. W. Fox, G. H. Moriarty-Schieven, P. A. Price

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


We present radio observations of the afterglow of the bright gamma-ray burst GRB 980703 made between 1 day and 1 yr after the burst. These data are combined with published late-time radio measurements and existing optical, near-infrared, and X-ray observations to create a comprehensive broadband data set for modeling the physical parameters of the outflow. While a wind-stratified medium cannot be ruled out statistically, it requires a high fraction of the shock energy in the electrons and so is not favored on theoretical grounds. Instead, the data are consistent with a fireball model in which the ejecta are collimated and expanding into a constant-density medium. The radio data cannot be fitted with an isotropic shock but instead require a jet break at ≈3.5 days, not seen at optical wavelengths because of the presence of a bright host galaxy. The addition of the full radio data set constrains the self-absorption frequency, giving an estimate of the circumburst density of n ≈ 30 cm-3, a value that differs substantially from previous estimates. This result is consistent with the growing number of GRB afterglows, for which broadband modeling yields n ≃ 0.1-100 cm -3, with a typical value of ∼10 cm-3.

Original languageAmerican English
Pages (from-to)992-998
Number of pages7
JournalAstrophysical Journal
Issue number2 I
StatePublished - 20 Jun 2003
Externally publishedYes


  • Gamma rays: bursts


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