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

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

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 languageEnglish (US)
Pages (from-to)992-998
Number of pages7
JournalAstrophysical Journal
Volume590
Issue number2 I
DOIs
StatePublished - Jun 20 2003

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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