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Title: Optical and radio observations of the afterglow from GRB 990510: evidence for a jet
Authors: Harrison, F.A.
Bloom, J.S.
Frail, D.A.
Sari, R.
Kulkarni, S.R.
Djorgovski, S.G.
Axelrod, T.
Mould, J.
Schmidt, B.P.
Wieringa, M.H.
Wark, R.M.
Subrahmanyan, Ravi
McConnell, D.
McCarthy, P.J.
Schaefer, B.E.
McMahon, R.G.
Markze, R.O.
Firth, E.
Soffitta, P.
Amati, L.
Keywords: cosmology
gamma rays
radio continuum
shock waves
Issue Date: Oct-1999
Publisher: The University of Chicago Press for the American Astronomical Society
Citation: Astrophysical Journal, 1999, Vol.523, pL121
Abstract: 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 theta_0=0.08(n/1 cm^-3)^1/8, reducing the isotropic gamma-ray energy release of 2.9x10^53 ergs by a factor of ~300.
Description: Restricted Access.
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Copyright: 1999 American Astronomical Society
Appears in Collections:Research Papers (A&A)

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