TY - JOUR
T1 - The unusual afterglow of the gamma-ray burst 100621A
AU - Greiner, J.
AU - Krühler, T.
AU - Nardini, M.
AU - Filgas, R.
AU - Moin, A.
AU - De Breuck, C.
AU - Montenegro-Montes, F.
AU - Lundgren, A.
AU - Klose, S.
AU - Fonso, P. M.J.
AU - Bertoldi, F.
AU - Elliott, J.
AU - Kann, D. A.
AU - Knust, F.
AU - Menten, K.
AU - Nicuesa Guelbenzu, A.
AU - Olivares, F. E.
AU - Rau, A.
AU - Rossi, A.
AU - Schady, P.
AU - Schmidl, S.
AU - Siringo, G.
AU - Spezzi, L.
AU - Sudilovsky, V.
AU - Tingay, S. J.
AU - Updike, A. C.
AU - Wang, Z.
AU - Weiss, A.
AU - Wieringa, M.
AU - Wyrowski, F.
N1 - Funding Information:
J.G. expresses special thanks to A. Vlasis for discussing some details of the shell collision scenario. We are grateful to ESO for approving the DDT proposal for APEX observations. Particular thanks to A. Kaufer for the support in the scheduling discussions for technical and Chilean time. A.M. was a fully sponsored Ph.D. candidate at ICRAR − Curtin University until 2011 and acknowledges the support of SHAO as a postdoctoral research fellow. We are similarly grateful to P. Edwards for approving and scheduling the ATCA ToO and regular observations. T.K. acknowledges support by the DFG cluster of excellence “Origin and Structure of the Universe” during the early part of this project when being employed at MPE, and AU is grateful for travel funding support through MPE. F.O.E. acknowledges funding of his Ph.D. through the Deutscher Akademischer Austausch-Dienst (DAAD), S.K. and A. Rossi acknowledge support by DFG grant Kl 766/13-2, and S.K., A. Rossi, A.N.G. and D.A.K. acknowledge support by DFG grant Kl 766/16-1. ARossi additionally acknowledges support from the BLANCEFLOR Boncompagni-Ludovisi, née Bildt foundation, and through the Jenaer Graduiertenakademie. M.N acknowledges support by DFG grant SA 2001/2-1. Part of the funding for GROND (both hardware and personnel) was generously granted from the Leibniz-Prize to Prof. G. Hasinger (DFG grant HA 1850/28-1). The Dark Cosmology Center (TK) is funded by the Danish National Research Foundation. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. Facilities: Max Planck:2.2 m (GROND), Swift
PY - 2013/12
Y1 - 2013/12
N2 - Aims. With the afterglow of GRB 100621A being the brightest detected so far in X-rays, and superb GROND coverage in the optical/near-infrared during the first few hours, an observational verification of basic fireball predictions seemed possible. Methods. In order to constrain the broad-band spectral energy distribution of the afterglow of GRB 100621A, dedicated observations were performed in the optical/near-infrared with the 7-channel Gamma-Ray Burst Optical and Near-infrared Detector (GROND) at the 2.2 m MPG/ESO telescope, in the sub-millimeter band with the large bolometer array LABOCA at APEX, and at radio frequencies with ATCA. Utilizing also Swift X-ray observations, we attempt an interpretation of the observational data within the fireball scenario. Results. The afterglow of GRB 100621A shows a very complex temporal and spectral evolution. We identify three different emission components, the most spectacular one causing a sudden intensity jump about one hour after the prompt emission. The spectrum of this component is much steeper than the canonical afterglow. We interpret this component using a two-shell collision prescription after the first shell has been decelerated by the circumburst medium. We use the fireball scenario to derive constraints on the microphysical parameters of the first shell. Long-term energy injection into a narrow jet seems to provide an adequate description. Another noteworthy result is the large (AV = 3.6 mag) line-of-sight host extinction of the afterglow in an otherwise extremely blue host galaxy. Conclusions. Some GRB afterglows have shown complex features, and that of GRB 100621A is another good example. Yet, detailed observational campaigns of the brightest afterglows promise to deepen our understanding of the formation of afterglows and the subsequent interaction with the circumburst medium.
AB - Aims. With the afterglow of GRB 100621A being the brightest detected so far in X-rays, and superb GROND coverage in the optical/near-infrared during the first few hours, an observational verification of basic fireball predictions seemed possible. Methods. In order to constrain the broad-band spectral energy distribution of the afterglow of GRB 100621A, dedicated observations were performed in the optical/near-infrared with the 7-channel Gamma-Ray Burst Optical and Near-infrared Detector (GROND) at the 2.2 m MPG/ESO telescope, in the sub-millimeter band with the large bolometer array LABOCA at APEX, and at radio frequencies with ATCA. Utilizing also Swift X-ray observations, we attempt an interpretation of the observational data within the fireball scenario. Results. The afterglow of GRB 100621A shows a very complex temporal and spectral evolution. We identify three different emission components, the most spectacular one causing a sudden intensity jump about one hour after the prompt emission. The spectrum of this component is much steeper than the canonical afterglow. We interpret this component using a two-shell collision prescription after the first shell has been decelerated by the circumburst medium. We use the fireball scenario to derive constraints on the microphysical parameters of the first shell. Long-term energy injection into a narrow jet seems to provide an adequate description. Another noteworthy result is the large (AV = 3.6 mag) line-of-sight host extinction of the afterglow in an otherwise extremely blue host galaxy. Conclusions. Some GRB afterglows have shown complex features, and that of GRB 100621A is another good example. Yet, detailed observational campaigns of the brightest afterglows promise to deepen our understanding of the formation of afterglows and the subsequent interaction with the circumburst medium.
KW - Gamma-ray burst: general
KW - Gamma-ray burst: individual: GRB 100621A
KW - Techniques: photometric
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U2 - 10.1051/0004-6361/201321284
DO - 10.1051/0004-6361/201321284
M3 - Article
AN - SCOPUS:84890099841
SN - 0004-6361
VL - 560
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A70
ER -