Precursors in
                    <i>Swift</i>
                    Gamma Ray Bursts with Redshift

Burlon, D.; Ghirlanda, G.; Ghisellini, G.; Lazzati, Davide; Nava, Lara; Nardini, M.; Celotti, A.

doi:10.1086/592350

Cited by 97 publications

(120 citation statements)

References 21 publications

(18 reference statements)

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“…If this process is related to a delayed reactivation of the central engine, this could produce an observable signature at higher frequencies around the new t 0,2 . The existence of prompt GRB light-curves showing long periods of quiescence between separate peaks lasting up to a few hundreds seconds has already been discussed in the literature (Ramirez-Ruiz et al 2001;Romano et al 2006;Burlon et al 2008Burlon et al , 2009Gruber et al 2010). Most of them are precursors (i.e., peaks preceding the main GRB event), but Burlon et al (2008) report on the case of GRB 060210 where two postcursors are observed 60 and 150 s after the end of the main burst.…”

Section: Discussionmentioning

confidence: 84%

“…The existence of prompt GRB light-curves showing long periods of quiescence between separate peaks lasting up to a few hundreds seconds has already been discussed in the literature (Ramirez-Ruiz et al 2001;Romano et al 2006;Burlon et al 2008Burlon et al , 2009Gruber et al 2010). Most of them are precursors (i.e., peaks preceding the main GRB event), but Burlon et al (2008) report on the case of GRB 060210 where two postcursors are observed 60 and 150 s after the end of the main burst. There is no clear example with later time (t ≥ 1500 s) post-cursors, although faint late-time peaks are hardly detectable by BAT (see Holland et al 2010, for a possible candidate).…”

Section: Discussionmentioning

confidence: 84%

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

Nardini

Greiner

Krühler

et al. 2011

A&A

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Context. After the launch of the Swift satellite, the gamma-ray burst (GRB) optical light-curve smoothness paradigm has been questioned thanks to the faster and better sampled optical follow-up, which has unveiled a very complex behaviour. This complexity is triggering the interest of the whole GRB community. The GROND multi-channel imager is used to study optical and near-infrared (NIR) afterglows of GRBs with unprecedented optical and near-infrared temporal and spectral resolution. The GRB 081029 has a very prominent optical rebrightening event and is an outstanding example of the application of the multi-channel imager to GRB afterglows. Aims. Here we exploit the rich GROND multi-colour follow-up of GRB 081029 combined with XRT observations to study the nature of late-time rebrightenings that appear in the optical-NIR light-curves of some GRB afterglows. Methods. We analyse the optical and NIR observations obtained with the seven-channel Gamma-Ray burst Optical and Near-infrared Detector (GROND) at the 2.2 m MPI/ESO telescope and the X-ray data obtained with the XRT telescope on board the Swift observatory. The multi-wavelength temporal and spectral evolution is discussed in the framework of different physical models. Results. The extremely steep optical and NIR rebrightening observed in GRB 081029 cannot be explained in the framework of the standard forward shock afterglow model. The absence of a contemporaneous X-ray rebrightening and the evidence of a strong spectral evolution in the optical-NIR bands during the rise suggest two separate components that dominate in the early and late-time lightcurves, respectively. The steepness of the optical rise cannot be explained even in the framework of the alternative scenarios proposed in the literature unless a late-time activity of the central engine is assumed.

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Section: Discussionmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 84%

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

Nardini

Greiner

Krühler

et al. 2011

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“…Burlon et al 2008, and references therein). Episodes 1 and 2 are not temporally separated by a quiescent time.…”

Section: Discussionmentioning

confidence: 99%

A double component in GRB 090618: a proto-black hole and a genuinely long gamma-ray burst

Izzo

Ruffini

Penacchioni

et al. 2012

A&A

117

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Context. The joint X-ray and gamma-ray observations of GRB 090618 by very many satellites offer an unprecedented possibility of testing crucial aspects of theoretical models. In particular, they allow us to test (a) in the process of gravitational collapse, the formation of an optically thick e + e − -baryon plasma self-accelerating to Lorentz factors in the range 200 < Γ < 3000; (b) its transparency condition with the emission of a component of 10 53−54 baryons in the TeV region and (c) the collision of these baryons with the circumburst medium (CBM) clouds, characterized by dimensions of 10 15−16 cm. In addition, these observations offer the possibility of testing a new understanding of the thermal and power-law components in the early phase of this GRB. Aims. We test the fireshell model of GRBs in one of the closest (z = 0.54) and most energetic (E iso = 2.90 × 10 53 erg) GRBs, namely GRB 090618. It was observed at ideal conditions by several satellites, namely Fermi, Swift, Konus-WIND, AGILE, RT-2, and Suzaku, as well as from on-ground optical observatories. Methods. We analyzed the emission from GRB 090618 using several spectral models, with special attention to the thermal and powerlaw components. We determined the fundamental parameters of a canonical GRB within the context of the fireshell model, including the identification of the total energy of the e + e − plasma, E e + e − tot , the proper GRB (P-GRB), the baryon load, the density and structure of the CBM. Results. We find evidence of the existence of two different episodes in GRB 090618. The first episode lasts 50 s and is characterized by a spectrum consisting of a thermal component, which evolves between kT = 54 keV and kT = 12 keV, and a power law with an average index γ = 1.75 ± 0.04. The second episode, which lasts for ∼100 s, behaves as a canonical long GRB with a Lorentz gamma factor at transparency of Γ = 495, a temperature at transparency of 29.22 keV and with a characteristic size of the surrounding clouds of R cl ∼ 10 15−16 cm and masses of ∼10 22−24 g. Conclusions. We support the recently proposed two-component nature of GRB 090618, namely, episode 1 and episode 2, with a specific theoretical analysis. We furthermore illustrate that episode 1 cannot be considered to be either a GRB or a part of a GRB event, but it appears to be related to the progenitor of the collapsing bare core, leading to the formation of the black hole, which we call a "proto-black hole". Thus, for the first time, we are witnessing the process of formation of a black hole from the phases just preceding the gravitational collapse all the way up to the GRB emission.

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“…From the observational point of view, long periods of quiescence of the central engine, lasting up to thousands of seconds, have been observed in a fraction of GRBs showing the so called pre-or post-cursors in their prompt gamma-ray emission phase (Ramirez-Ruiz et al 2001;Romano et al 2006;Burlon et al 2008Burlon et al , 2009Gruber et al 2010). If these gamma-ray emission episodes are associated with the acceleration of different shells with respect to the main prompt event, these are supposed to interact with the latter ones, probably leading to an observable optical flux rebrightening if the difference in Γ is large enough.…”

Section: Ultrarelativistic Shell Collisionmentioning

confidence: 99%

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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Precursors in Swift Gamma Ray Bursts with Redshift

Cited by 97 publications

References 21 publications

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

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

A double component in GRB 090618: a proto-black hole and a genuinely long gamma-ray burst

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

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