GRB 091024a and the Nature of Ultra-Long Gamma-Ray Bursts

Virgili, Fabio; Mundell, C. G.; Pal'Shin, V.; Guidorzi, C.; Margutti, R.; Melandri, A.; Harrison, R. M.; Kobayashi, S.; Chornock, R.; Henden, A. A.; Updike, A. C.; Cenko, S. Bradley; Tanvir, N. R.; Steele, I. A.; Cucchiara, Antonino; Gomboc, A.; Levan, A. J.; Cano, Z.; Mottram, Chris; Clay, N. R.; Bersier, D.; Kopač, D.; Japelj, J.; Filippenko, A. V.; Li, W.; Svinkin, D.; Golenetskii, S.; Hartmann, D. H.; Milne, Peter; Williams, G. G.; O’Brien, P. T.; Fox, D. B.; Berger, E.

doi:10.1088/0004-637x/778/1/54

Cited by 82 publications

(81 citation statements)

References 119 publications

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“…It might be wondered whether this holds for so-called ultralong events (Levan et al 2014;Gendre et al 2013;Stratta et al 2013;Virgili et al 2013;Zhang et al 2014;Boer et al 2015). We therefore report our results on 130925A (Evans et al 2014;Piro et al 2014), although Swift-BAT data do not cover it in its entirety.…”

Section: Dominant Timescale Vs Durationmentioning

confidence: 93%

Individual power density spectra ofSwiftgamma-ray bursts

Guidorzi

Dichiara

Amati

2016

A&A

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Context. Timing analysis can be a powerful tool with which to shed light on the still obscure emission physics and geometry of the prompt emission of gamma-ray bursts (GRBs). Fourier power density spectra (PDS) characterise time series as stochastic processes and can be used to search for coherent pulsations and, more in general, to investigate the dominant variability timescales in astrophysical sources. Because of the limited duration and of the statistical properties involved, modelling the PDS of individual GRBs is challenging, and only average PDS of large samples have been discussed in the literature thus far. Aims. We aim at characterising the individual PDS of GRBs to describe their variability in terms of a stochastic process, to explore their variety, and to carry out for the first time a systematic search for periodic signals and for a link between PDS properties and other GRB observables.Methods. We present a Bayesian procedure that uses a Markov chain Monte Carlo technique and apply it to study the individual PDS of 215 bright long GRBs detected with the Swift Burst Alert Telescope in the 15−150 keV band from January 2005 to May 2015. The PDS are modelled with a power-law either with or without a break. Results. Two classes of GRBs emerge: with or without a unique dominant timescale. A comparison with active galactic nuclei (AGNs) reveals similar distributions of PDS slopes. Unexpectedly, GRBs with subsecond-dominant timescales and duration longer than a few tens of seconds in the source frame appear to be either very rare or altogether absent. Three GRBs are found with possible evidence for a periodic signal at 3.0-3.2σ (Gaussian) significance, corresponding to a multi-trial chance probability of ∼1%. Thus, we found no compelling evidence for periodic signal in GRBs. Conclusions. The analogy between the PDS of GRBs and of AGNs could tentatively indicate similar stochastic processes that rule BH accretion across different BH mass scales and objects. In addition, we find evidence that short dominant timescales and duration are not completely independent of each other, in contrast with commonly accepted paradigms.

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Section: Dominant Timescale Vs Durationmentioning

confidence: 93%

Individual power density spectra ofSwiftgamma-ray bursts

Guidorzi

Dichiara

Amati

2016

A&A

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“…However, there are two detections (GRB100316D and GRB101024A) that occurred before the BAT trigger times. Within these detections, 7 GRBs are previously classified as ultralong GRBs, which are GRB121027A, GRB111215A, GRB111209A, GRB101225A, GRB100316D, GRB 090417B, GRB060218 (e.g., Gendre et al 2013;Virgili et al 2013;Levan et al 2014;Boër et al 2015). Studies usually refer "ultra-long GRBs" to bursts with durations  kiloseconds (e.g., Gendre et al 2013;Stratta et al 2013;Evans et al 2014;Levan et al 2014;Boër et al 2015), however, no unified definition has been adopted.…”

Section: False-detection Rate: Searching For Weak Emissionmentioning

confidence: 99%

The Third Swift Burst Alert Telescope Gamma-Ray Burst Catalog

Lien

Sakamoto

Barthelmy

et al. 2016

ApJ

310

320

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To date, the Burst Alert Telescope (BAT) onboard Swift has detected ∼1000 gamma-ray bursts (GRBs), of which ∼360 GRBs have redshift measurements, ranging from z=0.03 to z=9.38. We present the analyses of the BATdetected GRBs for the past ∼11 years up through GRB151027B. We report summaries of both the temporal and spectral analyses of the GRB characteristics using event data (i.e., data for each photon within approximately 250 s before and 950 s after the BAT trigger time), and discuss the instrumental sensitivity and selection effects of GRB detections. We also explore the GRB properties with redshift when possible. The result summaries and data products are available at http://swift.gsfc.nasa.gov/results/batgrbcat/index.html. In addition, we perform searches for GRB emissions before or after the event data using the BAT survey data. We estimate the false detection rate to be only one false detection in this sample. There are 15 ultra-long GRBs (∼2% of the BAT GRBs) in this search with confirmed emission beyond ∼1000 s of event data, and only two GRBs (GRB100316D and GRB101024A) with detections in the survey data prior to the starting of event data.

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“…Evidence of emission up to ∼1000 s after the trigger has been revealed A&A 567, A84 (2014) which showed highly variable γ-and X-ray emission extending over ∼20 ks (Evans et al 2014). These GRBs can be interpreted as the tail of the distribution of long GRBs (Virgili et al 2013). …”

Section: Introductionmentioning

confidence: 98%

GRB 120711A: an intense INTEGRAL burst with long-lasting softγ-ray emission and a powerful optical flash

Martín-Carrillo

Hanlon

Topinka

et al. 2014

A&A

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A long and intense γ-ray burst (GRB) was detected by INTEGRAL on 11 July 2012 with a duration of ∼115 s and fluence of 2.8 × 10 −4 erg cm −2 in the 20 keV−8 MeV energy range. GRB 120711A was at z ∼ 1.405 and produced soft γ-ray emission (>20 keV) for at least ∼10 ks after the trigger. The GRB was observed by several ground-based telescopes that detected a powerful optical flash peaking at an R-band brightness of ∼11.5 mag at ∼126 s after the trigger, or ∼9th magnitude when corrected for the host galaxy extinction (A V ∼ 0.85). The X-ray afterglow was monitored by the Swift, XMM-Newton, and Chandra observatories from 8 ks to 7 Ms and provides evidence for a jet break at ∼0.9 Ms. We present a comprehensive temporal and spectral analysis of the long-lasting soft γ-ray emission detected in the 20−200 keV band with INTEGRAL/IBIS, the Fermi/LAT post-GRB detection above 100 MeV, the soft X-ray afterglow and the optical/near-infrared detections from Watcher, Skynet/PROMPT, GROND, and REM. The prompt emission had a very hard spectrum (E peak ∼ 1 MeV) and yields an E γ,iso ∼ 10 54 erg (1 keV−10 MeV rest frame), making GRB 120711A one of the most energetic GRBs detected so far. We modelled the long-lasting soft γ-ray emission using the standard afterglow scenario, which indicates a forward shock origin. The combination of data extending from the near-infrared to GeV energies suggest that the emission is produced by a broken power-law spectrum consistent with synchrotron radiation. The afterglow is well modelled using a stratified wind-like environment with a density profile k ∼ 1.2, suggesting a massive star progenitor (i.e. Wolf-Rayet) with a mass-loss rate between ∼10 −5 −10 −6 M yr −1 depending on the value of the radiative efficiency (η γ = 0.2 or 0.5). The analysis of the reverse and forward shock emission reveals an initial Lorentz factor of ∼120−340, a jet half-opening angle of ∼2 • −5 • , and a baryon load of ∼10 −5 −10 −6 M consistent with the expectations of the fireball model when the emission is highly relativistic. Long-lasting soft γ-ray emission from other INTEGRAL GRBs with high peak fluxes, such as GRB 041219A, was not detected, suggesting that a combination of high Lorentz factor, emission above 100 MeV, and possibly a powerful reverse shock are required. Similar long-lasting soft γ-ray emission has recently been observed from the nearby and extremely bright Fermi/LAT burst GRB 130427A.

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GRB 091024a and the Nature of Ultra-Long Gamma-Ray Bursts

Cited by 82 publications

References 119 publications

Individual power density spectra ofSwiftgamma-ray bursts

Individual power density spectra ofSwiftgamma-ray bursts

The Third Swift Burst Alert Telescope Gamma-Ray Burst Catalog

GRB 120711A: an intense INTEGRAL burst with long-lasting softγ-ray emission and a powerful optical flash

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