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GRB 000418: A Hidden Jet Revealed

Berger, E. and Diercks, A. and Frail, D. A. and Kulkarni, S. R. and Bloom, J. S. and Sari, R. and Halpern, J. and Mirabal, N. and Taylor, G. B. and Hurley, K. and Pooley, G. and Becker, K. M. and Wagner, R. M. and Terndrup, D. M. and Statler, T. and Wik, D. R. and Mazets, E. and Cline, T. (2001) GRB 000418: A Hidden Jet Revealed. Astrophysical Journal, 556 (2). pp. 556-561. ISSN 0004-637X. doi:10.1086/321612.

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We report on optical, near-infrared, and centimeter radio observations of GRB 000418 that allow us to follow the evolution of the afterglow from 2 to 200 days after the γ-ray burst (GRB). In modeling these broadband data, we find that an isotropic explosion in a constant-density medium is unable to simultaneously fit both the radio and optical data. However, a jetlike outflow into either a constant density or wind-stratified medium with an opening angle of 10°-20° provides a good description of the data. The evidence in favor of a jet interpretation is based on the behavior of the radio light curves, since the expected jet break is masked at optical wavelengths by the light of the host galaxy. We also find evidence for extinction, presumably arising from within the host galaxy, with Aimg1.gif = 0.4 mag, as well as host flux densities of FR = 1.1 μJy and FK = 1.7 μJy. These values supersede previous work on this burst as a result of the availability of a broadband data set allowing a global fitting approach. A model in which the GRB explodes isotropically into a wind-stratified circumburst medium cannot be ruled out by these data. However, in examining a sample of other bursts (e.g., GRB 990510, GRB 000301C), we favor the jet interpretation for GRB 000418.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Berger, E.0000-0002-9392-9681
Kulkarni, S. R.0000-0001-5390-8563
Bloom, J. S.0000-0002-7777-216X
Sari, R.0000-0002-1084-3656
Taylor, G. B.0000-0001-6495-7731
Wik, D. R.0000-0001-8952-676X
Additional Information:© 2001. The American Astronomical Society. Received 2001 February 15; accepted 2001 April 5. A. D. is supported by a Millikan Fellowship at Caltech. GRB research at Caltech is supported by National Science Foundation and NASA grants (S. R. K.). K. H. is grateful for Ulysses support under JPL contract 958056 and for NEAR support under NAG 5-9503.
Funding AgencyGrant Number
Robert A. Millikan FellowshipUNSPECIFIED
NASANAG 5-9503
Subject Keywords:gamma rays: bursts; infrared: general; radio continuum: general
Issue or Number:2
Record Number:CaltechAUTHORS:20170408-163356661
Persistent URL:
Official Citation:E. Berger et al 2001 ApJ 556 556
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76210
Deposited By: 1Science Import
Deposited On:07 Mar 2018 19:40
Last Modified:15 Nov 2021 16:58

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