Optical and radio observations of the afterglow from GRB 990510: Evidence for a jet

F. A. Harrison*, J. S. Bloom, D. A. Frail, R. Sari, S. R. Kulkarni, S. G. Djorgovski, T. Axelrod, J. Mould, B. P. Schmidt, M. H. Wieringa, R. M. Wark, R. Subrahmanyan, D. McConnell, P. J. McCarthy, B. E. Schaefer, R. G. McMahon, R. O. Markze, E. Firth, P. Soffitta, L. Amati

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

227 Scopus citations


We present multicolor optical and two-frequency radio observations of the bright BeppoSAX event GRB 990510. Neither the well-sampled optical decay nor the radio observations are consistent with simple spherical afterglow models. The achromatic steepening in the optical band and the early decay of the radio afterglow, which both occur at t ∼ 1 day, are evidence for hydrodynamical evolution of the source and can be most easily interpreted by models in which the gamma-ray burst ejecta are collimated in a jet. Employing a simple jet model to explain the observations, we derive a jet opening angle of θ0 = 0.08(n/l cm-3)1/8, reducing the isotropic gamma-ray energy release of 2.9 × 1053 ergs by a factor of ∼300.

Original languageAmerican English
Pages (from-to)L121-L124
JournalAstrophysical Journal
Issue number2 PART 2
StatePublished - 1 Oct 1999
Externally publishedYes

Bibliographical note

Funding Information:
We thank Scott Barthelmy for operating the GCN, the staffs of LCO, MSSSO, and ATCA, and the entire BeppoSAX team. This work was supported by grants from NSF (S. R. K. and S. G. D.), NASA (F. A. H. and S. R. K.), and the Bressler Foundation (S. G. D.).


  • Cosmology: miscellaneous
  • Gamma rays: bursts
  • Radio continuum: general
  • Shock waves


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