Yuan, F. and Schady, P. and Racusin, J. L. and Willingale, R. and Krühler, T. and O'Brien, P. T. and Greiner, J. and Oates, S. R. and Rykoff, E. S. and Aharonian, F. and Akerlof, C. W. and Ashley, M. C. B. and Barthelmy, S. D. and Filgas, R. and Flewelling, H. A. and Gehrels, N. and Göğüş, E. and Güver, T. and Horns, D. and Kiziloǧlu, Ü. and Krimm, H. A. and McKay, T. A. and Özel, M. E. and Phillips, A. and Quimby, R. M. and Rowell, G. and Rujopakarn, W. and Schaefer, B. E. and Vestrand, W. T. and Wheeler, J. C. and Wren, J. (2010) GRB 081008: From Burst to Afterglow and the Transition Phase in Between. Astrophysical Journal, 711 (2). pp. 870-880. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20100316-103507720
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We present a multi-wavelength study of GRB 081008, at redshift 1.967, by Swift, ROTSE-III, and Gamma-Ray Burst Optical/NearInfrared Detector. Compared to other Swift GRBs, GRB 081008 has a typical gamma-ray isotropic equivalent energy output (~10^(53) erg) during the prompt phase, and displayed two temporally separated clusters of pulses. The early X-ray emission seen by the Swift X-Ray Telescope was dominated by the softening tail of the prompt emission, producing multiple flares during and after the Swift Burst Alert Telescope detections. Optical observations that started shortly after the first active phase of gamma-ray emission showed two consecutive peaks. We interpret the first optical peak as the onset of the afterglow associated with the early burst activities. A second optical peak, coincident with the later gamma-ray pulses, imposes a small modification to the otherwise smooth light curve and thus suggests a minimal contribution from a probable internal component. We suggest the early optical variability may be from continuous energy injection into the forward shock front by later shells producing the second epoch of burst activities. These early observations thus provide a potential probe for the transition from the prompt phase to the afterglow phase. The later light curve of GRB 081008 displays a smooth steepening in all optical bands and X-ray. The temporal break is consistent with being achromatic at the observed wavelengths. Our broad energy coverage shortly after the break constrains a spectral break within optical. However, the evolution of the break frequency is not observed. We discuss the plausible interpretations of this behavior.
|Additional Information:||© 2010 The American Astronomical Society. Received 2009 September 3; accepted 2010 January 26; published 2010 February 18. F.Y. gratefully acknowledges useful discussions with S. B. Pandey. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. F.Y. is supported by the NASA Swift Guest Investigator grants NNX-08AN25G. J.L.R. acknowledges support for this work from NASA contract NAS5-00136. R.W. and P.T.O. gratefully acknowledge funding from the STFC for Swift at the University of Leicester. T.K. acknowledges support by the DFG cluster of excellence “Origin and Structure of the Universe.” ROTSE-III has been supported by NASA grant NNX-08AV63G, NSF grant PHY-0801007, the Australian Research Council, the University of New South Wales, the University of Texas, and the University of Michigan. Special thanks to the H.E.S.S. staff, especially Toni Hanke. Part of the funding for GROND (both hardware as well as personnel) was generously granted from the Leibniz-Prize (DFG grant HA 1850/28-1) to Professor G. Hasinger (IPP).|
|Subject Keywords:||gamma-ray burst: individual (GRB 081008, GRB 081008, GRB 081008, GRB 081008, GRB 081008)|
|Official Citation:||GRB 081008: From Burst to Afterglow and the Transition Phase in Between F. Yuan, P. Schady, J. L. Racusin, R. Willingale, T. Krühler, P. T. O'Brien, J. Greiner, S. R. Oates, E. S. Rykoff, F. Aharonian, C. W. Akerlof, M. C. B. Ashley, S. D. Barthelmy, R. Filgas, H. A. Flewelling, N. Gehrels, E. Göğüş, T. Güver, D. Horns, Ü. Kızıloǧlu, H. A. Krimm, T. A. McKay, M. E. Özel, A. Phillips, R. M. Quimby, G. Rowell, W. Rujopakarn, B. E. Schaefer, W. T. Vestrand, J. C. Wheeler, and J. Wren doi: 10.1088/0004-637X/711/2/870|
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|Deposited By:||Jason Perez|
|Deposited On:||16 Mar 2010 20:56|
|Last Modified:||26 Dec 2012 11:50|
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