Open AccessOptical and Radio Observations of the Afterglow from GRB 990510: Evidence for a Jet
Author(s) -
Fiona A. Harrison,
J. S. Bloom,
D. A. Frail,
Re’em Sari,
S. R. Kulkarni,
S. G. Djorgovski,
T. S. Axelrod,
J. R. Mould,
B. Schmidt,
M. H. Wieringa,
R. M. Wark,
R. Subrahmanyan,
D. McConnell,
Patrick J. McCarthy,
Bradley E. Schaefer,
R. G. McMahon,
R. O. Markze,
Andrew E. Firth,
P. Soffitta,
L. Amati
Publication year - 1999
Publication title -
the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.1086/312282
Subject(s) - afterglow , gamma ray burst , physics , astrophysics , jet (fluid) , ejecta , collimated light , brightness , astronomy , light curve , optics , supernova , laser , thermodynamics
We present multi-color optical and two-frequency radio observations of thebright SAX event, GRB 990510. The well-sampled optical decay, together with theradio observations are inconsistent with simple spherical afterglow models. Theachromatic optical steepening and the decay of the radio afterglow bothoccuring at $t \sim 1$ day are evidence for hydrodynamical evolution of thesource, and can be most easily interpreted by models where the GRB ejecta arecollimated in a jet. Employing a simple jet model to interpret theobservations, we derive a jet opening angle of $\theta_o = 0.08$, reducing theisotropic gamma-ray emission of $2.9 \times 10^{53}$ erg by a factor $\sim300$. If the jet interpretation is correct, we conclude that GRB observationsto-date are consistent with an energy for the central source of $E \lsim10^{52}$ erg.Comment: 12 pages, 2 figures. Version accepted for publication in ApJ Letter
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