On the nature of the extremely fast optical rebrightening of the afterglow of GRB 081029

Nardini, M.; Greiner, J.; Krühler, T.; Filgas, R.; Klose, S.; Afonso, P.; Clemens, C.; Guelbenzu, A. N.; Olivares, F.; Rau, A.; Rossi, A.; Updike, A. C.; Yoldaş, A.; Burlon, D.; Elliot, J. L.; Канн, Д. А.

doi:10.1051/0004-6361/201116814

Cited by 58 publications

(79 citation statements)

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“…3.4, we find the best-fit optical rise between 20 ks and 100 ks after the GRB trigger to be α reb ∼ −2.9. This high value is less extreme than α reb ∼ −8.2 and α reb ∼ −14 measured for GRB 081029 (Nardini et al 2011) and GRB 100621A (Nardini et al 2012;Greiner et al 2013), respectively, and agrees with both the typical values for FROAs reported (PV08) and with the late-bump rise steepnesses derived by Liang et al (2013) in their sample. Liang et al (2013) also found a good correlation between the optical luminosity at the rebrightening peak and the host frame peak time.…”

Section: Late Rebrighteningsupporting

confidence: 88%

“…Moreover, thanks to the rich coverage and the small uncertainties in the v, and u bands at ∼60 ks, we can identify the smaller-scale fluctuations around the rebrightening peak. Those wiggles are similar to the ones observed around the peak of the prominent optical rebrightenings of GRB 081029 and GRB 100621A discussed in Nardini et al (2011) and Greiner et al (2013), respectively. The late fading in the UVOT bands tracks the power-law decay observed in the bluer GROND bands well.…”

Section: Uvot Light Curvesupporting

confidence: 81%

“…Unlike for GRB 081029 (Nardini et al 2011) or 100621A (Greiner et al 2013), GROND was unable to follow the full rising phase since it occurred during daytime in Chile. This temporal window was in part covered by UVOT.…”

Section: Late Rebrighteningmentioning

confidence: 99%

“…One-component scenarios As extensively discussed in Nardini et al (2011), several interpretations have been proposed in the literature to explain the late-time optical rebrightenings in long GRB afterglows. Some Fig.…”

Section: Possible Interpretations Of the Late Rebrigteningmentioning

confidence: 99%

“…The simplistic idea that the optical afterglow can be described as the sum of two or three smoothly connected power-laws produced by synchrotron radiation in the framework of the standard externalshock model (see e.g., Laursen & Stanek 2003;Panaitescu et al 2006;Panaitescu 2007a,b) now fails to explain the complex Full GROND and UVOT photometry tables are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/A29 behaviour observed in a large portion of well-sampled events (see e.g. De Pasquale et al 2009;Ghisellini et al 2009;Kong et al 2010;Nardini et al 2010Nardini et al , 2011Filgas et al 2011a,b;Vlasis et al 2011). An important role in furnishing the rich data sets necessary for detailed emission mechanism testings is played by instruments such as the Gamma-Ray burst Optical Near-infrared Detector (GROND), a seven-band simultaneous optical to NIR imager mounted on the 2.2 m MPG/ESO telescope at La Silla observatory .…”

Section: Introductionmentioning

confidence: 99%

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Afterglow rebrightenings as a signature of a long-lasting central engine activity?

Nardini

Elliott

Filgas

et al. 2014

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Context. In the past few years the number of well-sampled optical to near-infrared (NIR) light curves of long gamma-ray bursts (GRBs) has greatly increased, particularly due to simultaneous multi-band imagers such as GROND. Combining these densely sampled ground-based data sets with the Swift UVOT and XRT space observations unveils a much more complex afterglow evolution than what was predicted by the most commonly invoked theoretical models. GRB 100814A represents a remarkable example of these interesting well-sampled events, showing a prominent late-time rebrightening in the optical to NIR bands and a complex spectral evolution. This represents a unique laboratory to test the different afterglow emission models. Aims. Here we study the nature of the complex afterglow emission of GRB 100814A in the framework of different theoretical models. Moreover, we compare the late-time chromatic rebrightening with those observed in other well-sampled long GRBs. Methods. We analysed the optical and NIR observations obtained with the seven-channel Gamma-Ray burst Optical and Near-infrared Detector (GROND) at the 2.2 m MPG/ESO telescope together with the X-ray and UV data detected by the instruments onboard the Swift observatory. The broad-band afterglow evolution, achieved by constructing multi-instrument light curves and spectral energy distributions, is discussed in the framework of different theoretical models. Results. We find that the standard models that describe the broad-band afterglow emission within the external shock scenario fail to describe the complex evolution of GRB 100814A, and therefore more complex scenarios must be invoked. The analysis of the very well sampled broad-band light curve of GRB 100814A allowed us to deduce that models invoking late-time activity of the central engine in the observed afterglow emission are the preferred ones for all the different observed features. This late-time activity most likely has the form of a delayed reactivation of the ejecta emission process. However, a more detailed modelling of the radiative mechanisms associated with these scenarios is necessary to arrive at a firm conclusion on the nature of the optical rebrightenings that so often are detected in long GRBs.

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