THE LATE PEAKING AFTERGLOW OF GRB 100418A
- Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, 20771 MD (United States)
- INAF-Astronomical Observatory of Rome, via Frascati 33, 00040 Monteporzio, Rome, (Italy)
- Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)
- INAF-Osservatorio Astronomico di Brera, via Emilio Bianchi 46, 23807, Merate (Italy)
- Mullard Space Science Laboratory (UCL), Holmbury Road, Holmbury St Mary, Dorking RH5 6NT (United Kingdom)
- Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)
- Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154-4002 (United States)
GRB 100418A is a long gamma-ray burst (GRB) at redshift z = 0.6235 discovered with the Swift Gamma-ray Burst Explorer with unusual optical and X-ray light curves. After an initial short-lived, rapid decline in X-rays, the optical and X-ray light curves observed with Swift are approximately flat or rising slightly out to at least {approx}7 x 10{sup 3} s after the trigger, peak at {approx}5 x 10{sup 4} s, and then follow an approximately power-law decay. Such a long optical plateau and late peaking is rarely seen in GRB afterglows. Observations with Rapid Eye Mount during a gap in the Swift coverage indicate a bright optical flare at {approx}2.5 x 10{sup 4} s. The long plateau phase of the afterglow is interpreted using either a model with continuous injection of energy into the forward shock of the burst or a model in which the jet of the burst is viewed off-axis. In both models the isotropic kinetic energy in the late afterglow after the plateau phase is {>=}10{sup 2} times the 10{sup 51} erg of the prompt isotropic gamma-ray energy release. The energy injection model is favored because the off-axis jet model would require the intrinsic T{sub 90} for the GRB jet viewed on-axis to be very short, {approx}10 ms, and the intrinsic isotropic gamma-ray energy release and the true jet energy to be much higher than the typical values of known short GRBs. The non-detection of a jet break up to t {approx} 2 x 10{sup 6} s indicates a jet half-opening angle of at least {approx}14{sup 0}, and a relatively high-collimation-corrected jet energy of E{sub jet} {>=} 10{sup 52} erg.
- OSTI ID:
- 21567526
- Journal Information:
- Astrophysical Journal, Vol. 727, Issue 2; Other Information: DOI: 10.1088/0004-637X/727/2/132; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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