Article

Optical and Radio Observations of the Afterglow from GRB 990510: Evidence for a Jet

Fiona A. HarrisonPalomar Observatory 105-24, California Institute of Technology, Pasadena, CA 91125J. S. BloomPalomar Observatory 105-24, California Institute of Technology, Pasadena, CA 91125D. A. FrailNational Radio Astronomy Observatory, Socorro, NM 87801Re’em SariCalifornia Institute of Technology, Theoretical Astrophysics 103-33, Pasadena, CA 91125S. R. KulkarniPalomar Observatory 105-24, California Institute of Technology, Pasadena, CA 91125S. G. DjorgovskiPalomar Observatory 105-24, California Institute of Technology, Pasadena, CA 91125T. S. AxelrodResearch School of Astronomy, Australian National University, Private Bag, Weston Creek P.O., ACT 2611, AustraliaJ. R. MouldResearch School of Astronomy, Australian National University, Private Bag, Weston Creek P.O., ACT 2611, AustraliaB. SchmidtResearch School of Astronomy, Australian National University, Private Bag, Weston Creek P.O., ACT 2611, AustraliaM. H. WieringaAustralian Telescope National Facility, CSIRO, Epping, NSW 2121, AustraliaR. M. WarkAustralian Telescope National Facility, CSIRO, Epping, NSW 2121, AustraliaR. SubrahmanyanAustralian Telescope National Facility, CSIRO, Epping, NSW 2121, AustraliaD. McConnellAustralian Telescope National Facility, CSIRO, Epping, NSW 2121, AustraliaPatrick J. McCarthyObservatories of the Carnegie Institute of Washington, 813 Santa Barbara Street, Pasadena, CA 91101-1292Bradley E. SchaeferDepartment of Physics, Yale University, New Haven, CT 06520R. G. McMahonInstitute of Astronomy, Madingley Road, Cambridge CB3 OHA, England, UKR. O. MarkzeObservatories of the Carnegie Institute of Washington, 813 Santa Barbara Street, Pasadena, CA 91101-1292Andrew E. FirthInstitute of Astronomy, Madingley Road, Cambridge CB3 OHA, England, UKP. SoffittaIstituto Astrofisica Spaziale, CNR, Area di Ricerca Tor Vergata, Via Fosso del Cavaliere 100, 00133 Roma, ItalyL. Amati

1999en

ABI

Abstract

We present multi-color optical and two-frequency radio observations of the bright SAX event, GRB 990510. The well-sampled optical decay, and the radio observations are both inconsistent with simple spherical afterglow models. The achromatic optical steepening and the decay of the radio afterglow both occuring at t ∼ 1 day are evidence for hydrodynamical evolution of the source, and can be most easily interpreted by models where the GRB ejecta are collimated in a jet. Employing a simple jet model to interpret the observations, we derive a jet opening angle of θo = 0.08, reducing the isotropic gamma-ray emission of 2.9 × 10 53 erg by a factor ∼ 300. If the jet interpretation is correct, we conclude that GRB observations to-date are consistent with an energy for the central source of E ∼ &lt; 10 52 erg. 1

Identifiers

DOI: 10.1086/312282

Citations and references

Cited by 20 references

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