A Strong Optical Flare Before the Rising Afterglow of GRB 080129

Greiner, J.; Krühler, T.; McBreen, S.; Ajello, M.; Giannios, Dimitrios; Schwarz, R.; Savaglio, S.; Yoldaş, A.; Clemens, C.; Stefanescu, A.; Sala, G.; Bertoldi, F.; Szokoly, G. P.; Klose, S.

doi:10.1088/0004-637x/693/2/1912

Cited by 149 publications

(154 citation statements)

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“…While there is evidence from well-sampled optical afterglow light-curves of chromatic evolution simultaneous to strong variability (e.g. Greiner et al 2009c), the associated color changes are generally moderate to absent even in complex panchromatic light-curves (e.g. Masetti et al 2000;Holland et al 2003;Covino et al 2003;Lipkin et al 2004;Racusin et al 2008;Updike et al 2008;Perley et al 2008;Bloom et al 2009;Krühler et al 2009a;Cenko et al 2009;Perley et al 2010;McBreen et al 2010;Kann et al 2010;Covino et al 2010).…”

Section: Data Reduction and Cross Calibrationmentioning

confidence: 99%

Photometric redshifts for gamma-ray burst afterglows from GROND andSwift/UVOT

Krühler

Schady

Greiner

et al. 2011

A&A

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Aims. We present a framework to obtain photometric redshifts (photo-zs) for gamma-ray burst afterglows. Using multi-band photometry from GROND and Swift/UVOT, photo-zs are derived for five GRBs for which spectroscopic redshifts are not available. Methods. We use UV/optical/NIR data and synthetic photometry based on afterglow observations and theory to derive the photometric redshifts of GRBs and their accuracy. Taking into account the afterglow synchrotron emission properties, we investigate the application of photometry to derive redshifts in a theoretical range between z ∼ 1 to z ∼ 12.Results. The measurement of photo-zs for GRB afterglows provides a quick, robust and reliable determination of the distance scale to the burst, particularly in those cases where spectroscopic observations in the optical/NIR range cannot be obtained. Given a sufficiently bright and mildly reddened afterglow, the relative photo-z accuracy η = Δz/(1 + z) is better than 10% between z = 1.5 and z ∼ 7 and better than 5% between z = 2 and z = 6. We detail the approach on 5 sources without spectroscopic redshifts observed with UVOT on-board Swift and/or GROND. The distance scale to those same afterglows is measured to be z = 4.31 +0.14 −0.15 for GRB 080825B, z = 2.13 +0.14 −0.20 for GRB 080906, z = 3.44 +0.15 −0.32 for GRB 081228, z = 2.03 +0.16 −0.14 for GRB 081230 and z = 1.28 +0.16 −0.15 for GRB 090530. Conclusions. Due to the exceptional luminosity and simple continuum spectrum of GRB afterglows, photometric redshifts can be obtained to an accuracy as good as η ∼ 0.03 over a large redshift range including robust (η ∼ 0.1) measurements in the ultra-high redshift regime (z 7). Combining the response from UVOT with ground-based observatories and in particular GROND operating in the optical/NIR wavelength regime, reliable photo-zs can be obtained from z ∼ 1.0 out to z ∼ 10, and possibly even at higher redshifts in some favorable cases, provided that these GRBs exist, are localized quickly, have sufficiently bright afterglows and are not heavily obscured.

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Section: Data Reduction and Cross Calibrationmentioning

confidence: 99%

Photometric redshifts for gamma-ray burst afterglows from GROND andSwift/UVOT

Krühler

Schady

Greiner

et al. 2011

A&A

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“…However, afterglow light curves often display complex temporal behaviour with shallow decays, plateaus, rebrightenings, flares or smooth breaks such that limited sampling strongly affects the inferred light-curve slope (e.g. Lipkin et al 2004;Nousek et al 2006;Evans et al 2009;Greiner et al 2009b). Hence, here and later, we derive the spectral index from the optical to NIR SED, and use the temporal index from the light curve fitting and the closure relations to obtain constraints on the jet properties.…”

Section: Spectral Energy Distributionmentioning

confidence: 99%

Optical and near-infrared follow-up observations of fourFermi/LAT GRBs: redshifts, afterglows, energetics, and host galaxies

McBreen

Krühler

Rau

et al. 2010

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Aims. Fermi can measure the spectral properties of gamma-ray bursts over a very large energy range and is opening a new window on the prompt emission of these energetic events. Localizations by the instruments on Fermi in combination with follow-up by Swift provide accurate positions for observations at longer wavelengths leading to the determination of redshifts, the true energy budget, host galaxy properties and facilitate comparison with pre-Fermi bursts. Methods. Multi-wavelength follow-up observations were performed on the afterglows of four bursts with high energy emission detected by Fermi/LAT: GRB 090323, GRB 090328, GRB 090510 and GRB 090902B. They were obtained in the optical/near-infrared bands with GROND mounted at the MPG/ESO 2.2 m telescope and additionally of GRB 090323 in the optical with the 2 m telescope in Tautenburg, Germany. Three of the events are classified as long bursts while GRB 090510 is a well localized short GRB with GeV emission. In addition, host galaxies were detected for three of the four bursts. Spectroscopic follow-up was initiated with the VLT for GRB 090328 and GRB 090510. Results. The afterglow observations in 7 bands are presented for all bursts and their host galaxies are investigated. Knowledge of the distance and the local dust extinction enables comparison of the afterglows of LAT-detected GRBs with the general sample. The spectroscopic redshifts of GRB 090328 and GRB 090510 were determined to be z = 0.7354 ± 0.0003 and z = 0.903 ± 0.001 and dust corrected star-formation rates of 4.8 M yr −1 and 0.60 M yr −1 were derived for their host galaxies, respectively. Conclusions. The afterglows of long bursts exhibit power-law decay indices (α) from less than 1 to ∼2.3 and spectral indices (β opt ) values from 0.65 to ∼1.2 which are fairly standard for GRB afterglows. Constraints are placed on the jet half opening angles of < ∼ 2.1 • to > ∼ 6.4 • , which allows limits to be placed on the beaming corrected energies. These range from < ∼ 5 × 10 50 erg to the one of the highest values ever recorded, > ∼ 2.2 × 10 52 erg for GRB 090902B, and are not consistent with a standard candle. The extremely energetic long Fermi bursts have optical afterglows which lie in the top half of the brightness distribution of all optical afterglows detected in the Swift era or even in the top 5% if incompleteness is considered. The properties of the host galaxies of these LAT detected bursts in terms of extinction, star formation rates and masses do not appear to differ from previous samples.

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“…Such high-precision data allow not only for a detailed study of afterglow light curves (Greiner et al 2009b;Nardini et al 2011) but also jets of GRBs (Krühler et al 2009), the dust in their host galaxies Küpcü Yoldaş et al 2010;Greiner et al 2011;Krühler et al 2011b), their redshifts (Greiner et al 2009a;Krühler et al 2011a) and much more.…”

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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A Strong Optical Flare Before the Rising Afterglow of GRB 080129

Cited by 149 publications

References 31 publications

Photometric redshifts for gamma-ray burst afterglows from GROND andSwift/UVOT

Photometric redshifts for gamma-ray burst afterglows from GROND andSwift/UVOT

Optical and near-infrared follow-up observations of fourFermi/LAT GRBs: redshifts, afterglows, energetics, and host galaxies

GRB 091127: The cooling break race on magnetic fuel

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