<i>Swift</i>Panchromatic Observations of the Bright Gamma‐Ray Burst GRB 050525a

Blustin, A. J.; Barthelmy, S. D.; Boyd, Patricia T.; Capalbi, M.; Holland, S. T.; Marshall, F. E.; Mason, K. O.; Perri, M.; Poole, T.; Roming, P. W. A.; Rosen, S. R.; Schady, P.; Still, M.; Zhang, Bing; Angelini, L.; Barbier, L.; Beardmore, A. P.; Breeveld, A. A.; Burrows, D. N.; Cummings, J. R.; Canizzo, J.; Campana, S.; Chester, M. M.; Chincarini, G.; Cominsky, L.; Cucchiara, Antonino; Pasquale, M. De; Fenimore, E.; Gehrels, N.; Giommi, P.; Goad, M. R.; Grönwall, C.; Grupe, D.; Hill, J. E.; Hinshaw, D. A.; Hunsberger, S.; Hurley, K.; Ivanushkina, M.; Kennea, J. A.; Krimm, H. A.; Kumar, Pawan; Landsman, W. B.; Parola, V. La; Markwardt, C.; McGowan, K.; Mészáros, P.; Mineo, T.; Moretti, A.; Morgan, A. N.; Nousek, J. A.; O’Brien, P. T.; Osborne, J. P.; Page, K. L.; Page, M. J.; Palmer, D. M.; Parsons, A.; Rhoads, James E.; Romano, P.; Sakamoto, T.; Sato, G.; Tagliaferri, G.; Tueller, J.; Wells, A.; White, N. E.

doi:10.1086/498425

Cited by 102 publications

(83 citation statements)

References 36 publications

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“…It is possible that in some GRBs (e.g., GRB 050525A; Blustin et al 2006) the XRT observations started too late to catch the prompt emission tail. Nonetheless, a small fraction of XRT light curves show an apparently smooth transition from the prompt emission to the afterglow emission without a steep decay bridge.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Testing the Curvature Effect and Internal Origin of Gamma‐Ray Burst Prompt Emissions and X‐Ray Flares withSwiftData

Liang

Zhang

O’Brien

et al. 2006

ApJ

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207

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The X-ray light curves of many GRBs have a steep tail following the gamma-rays and have some erratic flares. We assume that these tails and flares are of ''internal'' origin and that their decline behaviors are dominated by the curvature effect. This effect suggests that the decay slope of the late steep decay part of the light curves is ¼ 2 þ , where is the X-ray spectral index. We present a self-consistency test for this scenario with a sample of 36 prompt emission tails/flares in 22 light curves observed by the Swift XRT. We derive the zero time (t 0 ) for each steep decay component by fitting the light curves with the constraint of ¼ 2 þ . Our results show that the t 0 values of the prompt emission tails and the tails of well-separated flares are self-consistent with the expectation of the internal dissipation models, indicating that each X-ray flare forms a distinct episode of the central engine activity and the central engine remains active after the prompt emission is over, sometimes up to $1 day after the GRB trigger. This challenges the conventional models and calls for new ideas to restart the central engine. We further show that the onset time of the late central engine activity does not depend on the GRB duration. We also identify a minority group of GRBs whose combined BAT-XRT light curves are smoothly connected, without an abrupt transition between the prompt emission and the afterglow. These GRBs may have an external origin for both the prompt emission and the afterglow.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Testing the Curvature Effect and Internal Origin of Gamma‐Ray Burst Prompt Emissions and X‐Ray Flares withSwiftData

Liang

Zhang

O’Brien

et al. 2006

ApJ

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207

199

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“…Since its launch in 2004, Swift has provided many early and well-sampled afterglow light curves and X-ray spectra. Blustin et al (2006) for example fitted broad-band SEDs of the afterglow of GRB 050525A with a cooling break between early optical and X-ray data and with a simple power-law through later epochs, suggesting a spectral evolution. However, such sudden spectral change can sometimes be also attributed to another component with a different electron distribution present in the emission at later times (Filgas et al 2011).…”

Section: Introductionmentioning

confidence: 99%

GRB 091127: The cooling break race on magnetic fuel

Filgas

Greiner

Schady

et al. 2011

A&A

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Aims. Using high-quality, broad-band afterglow data for GRB 091127, we investigate the validity of the synchrotron fireball model for gamma-ray bursts (GRBs), and infer physical parameters of the ultra-relativistic outflow. Methods. We used multi-wavelength (NIR to X-ray) follow-up observations obtained with GROND simultaneously in the g r i z JH filters and the XRT onboard the Swift satellite in the 0.3 to 10 keV energy range. The resulting afterglow light curve is of excellent accuracy with relative photometric errors as low as 1%, and the spectral energy distribution (SED) is well-sampled over 5 decades in energy. These data present one of the most comprehensive observing campaigns for a single GRB afterglow and allow us to test several proposed emission models and outflow characteristics in unprecedented detail.Results. Both the multi-color light curve and the broad-band SED of the afterglow of GRB 091127 show evidence of a cooling break moving from high to lower energies. The early light curve is well described by a broken power-law, where the initial decay in the optical/NIR wavelength range is considerably flatter than at X-rays. Detailed fitting of the time-resolved SED shows that the break is very smooth with a sharpness index of 2.2 ± 0.2, and evolves towards lower frequencies as a power-law with index −1.23 ± 0.06. These are the first accurate and contemporaneous measurements of both the sharpness of the spectral break and its time evolution. Conclusions. The measured evolution of the cooling break (ν c ∝ t ∼−1.2 ) is not consistent with the predictions of the standard model, wherein ν c ∝ t ∼−0.5 is expected. A possible explanation for the observed behavior is a time dependence of the microphysical parameters, in particular the fraction of the total energy in the magnetic field B . This conclusion provides further evidence that the standard fireball model is too simplistic, and time-dependent micro-physical parameters may be required to model the growing number of well-sampled afterglow light curves.

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“…We finally note that there are several sources that exhibit optical light curves analogous to GRB 061121, that is, GRB 021004 (Uemura et al 2002), GRB 050525A (Klotz et al 2005;Blustin et al 2006), GRB 060117 (Jelínek et al 2006), GRB 060526 (Dai et al 2007), and GRB 061007 (Mundell et al 2007). For all of them, an early decay phase was terminated by a flattening or a hump at 10 2−4 s, which was followed by a steeper decay phase.…”

Section: Implication To the Synchrotron-shock Modelmentioning

confidence: 83%

“…Krühler et al (2009) report on optical-IR and X-ray light curves of GRB 080710, in which an achromatic break was observed. Blustin et al (2006) report another example of a possible achromatic break in GRB 050525A, while X-ray flares make it difficult to accurately determine a break time (also see, Klotz et al 2005). In some of past cases, optical observations were too sparse to determine break times and to capturethe detailed behavior on either side of the breaks.…”

Section: Introductionmentioning

confidence: 99%

Optical behavior of GRB 061121 around its X-Ray shallow decay phase

Uehara

Uemura

Arai

et al. 2011

A&A

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Aims. We report on a detailed study of the optical afterglow of GRB 061121 with our original time-series photometric data. Along with our optical observations and public X-ray data, we discuss the origin of its optical and X-ray afterglows. Methods. We observed the optical afterglow of Swift burst GRB 061121 with the Kanata 1.5-m telescope at Higashi-Hiroshima Observatory. Our observation covers a period just after an X-ray plateau phase. We also performed deep imaging with the Subaru telescope in 2010 in order to estimate the contamination by the host galaxy. Results. In the light curve, we find that the optical afterglow also exhibited a break as in the X-ray afterglow. However, our observation suggests a possible hump structure or a flattening period before the optical break in the light curve. There is no sign of such a hump in the X-ray light curve. Conclusions. This implies that the optical emitting region was distinct from the X-ray one. The hump in the optical light curve was possibly caused by a passage with the typical frequency of synchrotron emission from another forward shock distinct from the early afterglow. The observed decay and spectral indices are inconsistent with the standard synchrotron-shock model. As a results, the observation requires a change in microphysical parameters in the shock region or prior activity by the central engine. Alternatively, the emission during the shallow decay phase may be a composition of two forward shock emissions, as indicated by the hump structure in the light curve.

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SwiftPanchromatic Observations of the Bright Gamma‐Ray Burst GRB 050525a

Cited by 102 publications

References 36 publications

Testing the Curvature Effect and Internal Origin of Gamma‐Ray Burst Prompt Emissions and X‐Ray Flares withSwiftData

Testing the Curvature Effect and Internal Origin of Gamma‐Ray Burst Prompt Emissions and X‐Ray Flares withSwiftData

GRB 091127: The cooling break race on magnetic fuel

Optical behavior of GRB 061121 around its X-Ray shallow decay phase

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