<i>Fermi</i>/GBM observations of the ultra-long GRB 091024

Gruber, D.; Krühler, T.; Foley, S.; Nardini, M.; Burlon, D.; Rau, A.; Bissaldi, E.; Kienlin, A. von; McBreen, S.; Greiner, J.; Bhat, P. N.; Briggs, M. S.; Burgess, J. Michael; Chaplin, V.; Connaughton, V.; Diehl, R.; Fishman, G.; Gibby, M. H.; Giles, M. M.; Goldstein, A.; Guiriec, S.; Horst, A. J. van der; Kippen, R. M.; Kouveliotou, C.; Lin, L.; Meegan, C.; Pačiesas, W. S.; Preece, R.; Tierney, David L.; Wilson-Hodge, C.

doi:10.1051/0004-6361/201015891

Cited by 54 publications

(36 citation statements)

References 54 publications

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“…Moreover, most of the dissipation in internal shocks is expected to occur near the maximal Lorentz factor attained by the outflow. This would greatly help to satisfy the lower limits on that arise from compactness arguments, or from the onset of the afterglow emission (usually around a few hundred; Sari & Piran 1999;Nakar & Piran 2005;Molinari et al 2007;Rykoff et al 2009;Zou & Piran 2010;Gruber et al 2011), also for a stellar wind environment.…”

Section: Discussionmentioning

confidence: 99%

The effects of sub-shells in highly magnetized relativistic flows

Granot

2012

Monthly Notices of the Royal Astronomical Society

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Astrophysical sources of relativistic jets or outflows, such as gamma-ray bursts (GRBs), active galactic nuclei (AGN) or micro-quasars, often show strong time variability. Despite such impulsive behaviour, most models of these sources assume a steady state for simplicity. Here I consider a time-dependent outflow that is initially highly magnetized and divided into many well-separated sub-shells, as it experiences impulsive magnetic acceleration and interacts with the external medium. In AGN the deceleration by the external medium is usually unimportant and most of the initial magnetic energy is naturally converted into kinetic energy, leading to efficient dissipation in internal shocks as the sub-shells collide. Such efficient low-magnetization internal shocks can also naturally occur in GRBs, where the deceleration by the external medium can be important. A strong low-magnetization reverse shock can develop, and the initial division into sub-shells allows it to be relativistic and its emission to peak on the time-scale of the prompt GRB duration (which is not possible for a single shell). Sub-shells also enable the outflow to reach much higher Lorentz factors that help satisfy existing constraints on GRBs from intrinsic pair opacity and from the afterglow onset time

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Section: Discussionmentioning

confidence: 99%

The effects of sub-shells in highly magnetized relativistic flows

Granot

2012

Monthly Notices of the Royal Astronomical Society

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“…The Fermi-LAT and GBM data may be retrieved from the Fermi Science Support Center archives. 77,78 The GBM detectors were selected in the same fashion as outlined in Abdo et al (2009c), Gruber et al (2011), andGoldstein et al (2012): we used the sodium iodide (NaI) detectors 0 and 3, and bismuth germanate (BGO) detector 0. We also used Time Tagged Events data (Meegan et al 2009) for our spectral analysis with a temporal resolution of 64 ms, in the 8 keV to 40 MeV energy range, excluding the range around the NaI K-edge at 33.17 keV.…”

Section: Fermimentioning

confidence: 99%

MULTIWAVELENGTH OBSERVATIONS OF GRB 110731A: GeV EMISSION FROM ONSET TO AFTERGLOW

Ackermann¹,

Ajello²,

Asano³

et al. 2013

ApJ

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We report on the multiwavelength observations of the bright, long gamma-ray burst GRB 110731A, by the Fermi and Swift observatories, and by the MOA and GROND optical telescopes. The analysis of the prompt phase reveals that GRB 110731A shares many features with bright Large Area Telescope bursts observed by Fermi during the first three years on-orbit: a light curve with short time variability across the whole energy range during the prompt phase, delayed onset of the emission above 100 MeV, extra power-law component and temporally extended high-energy emission. In addition, this is the first GRB for which simultaneous GeV, X-ray, and optical data are available over multiple epochs beginning just after the trigger time and extending for more than 800 s, allowing temporal and spectral analysis in different epochs that favor emission from the forward shock in a wind-type medium. The observed temporally extended GeV emission is most likely part of the high-energy end of the afterglow emission. Both the single-zone pair transparency constraint for the prompt signal and the spectral and temporal analysis of the forward-shock afterglow emission independently lead to an estimate of the bulk Lorentz factor of the jet Γ ∼ 500-550.

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“…Fortunately, however, there exist tens of fortuitous cases in which both the gamma-ray emission and optical emission have been detected during the prompt period. These can be divided into three possible scenarios: (i) a wide-field camera is observing the same field position as a satellite and so catches the optical emission simultaneously (e.g., 080319B, 130427A; Racusin et al 2008;Bloom et al 2009;Beskin et al 2010;Wren et al 2013); (ii) the prompt period is long enough that optical instruments slew in time to observe the prompt period (e.g., 990123, 080928, 110205A, 091024; Akerlof et al 1999;Rossi et al 2011;Cucchiara et al 2011;Gruber et al 2011;Gendre et al 2012;Zheng et al 2012;Virgili et al 2013);and (iii) there is a precursor to the main event so that optical instruments can slew in time (e.g., 041219A, 050820A, 061121; Blake et al 2005;Vestrand et al 2005Vestrand et al , 2006Page et al 2007). Only recently has it become possible to compile samples of bursts that exhibit optical emission during the prompt phase (Kopač et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Prompt emission of GRB 121217A from gamma-rays to the near-infrared

Elliott

Schmidl

et al. 2014

A&A

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The mechanism that causes the prompt-emission episode of gamma-ray bursts (GRBs) is still widely debated despite there being thousands of prompt detections. The favoured internal shock model relates this emission to synchrotron radiation. However, it does not always explain the spectral indices of the shape of the spectrum, which is often fit with empirical functions, such as the Band function. Multi-wavelength observations are therefore required to help investigate the possible underlying mechanisms that causes the prompt emission. We present GRB 121217A, for which we were able to observe its near-infrared (NIR) emission during a secondary prompt-emission episode with the Gamma-Ray burst Optical Near-infrared Detector (GROND) in combination with the Swift and Fermi satellites, which cover an energy range of 5 orders of magnitude (10 −3 keV to 100 keV). We determine a photometric redshift of z = 3.1 ± 0.1 with a line-of-sight with little or no extinction (A V ∼ 0 mag) utilising the optical/NIR SED. From the afterglow, we determine a bulk Lorentz factor of Γ 0 ∼ 250 and an emission radius of R < 10 18 cm. The prompt-emission broadband spectral energy distribution is well fit with a broken power law with β 1 = −0.3 ± 0.1 and β 2 = 0.6 ± 0.1 that has a break at E = 6.6 ± 0.9 keV, which can be interpreted as the maximum injection frequency. Self-absorption by the electron population below energies of E a < 6 keV suggest a magnetic field strength of B ∼ 10 5 G. However, all the best fit models underpredict the flux observed in the NIR wavelengths, which also only rebrightens by a factor of ∼2 during the second prompt emission episode, in stark contrast to the X-ray emission, which rebrightens by a factor of ∼100. This suggests an afterglow component is dominating the emission. We present GRB 121217A, one of the few GRBs that has multi-wavelength observations of the prompt-emission period and shows that it can be understood with a synchrotron radiation model. However, due to the complexity of the GRB's emission, other mechanisms that result in Band-like spectra cannot be ruled out.

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Fermi/GBM observations of the ultra-long GRB 091024

Cited by 54 publications

References 54 publications

The effects of sub-shells in highly magnetized relativistic flows

The effects of sub-shells in highly magnetized relativistic flows

MULTIWAVELENGTH OBSERVATIONS OF GRB 110731A: GeV EMISSION FROM ONSET TO AFTERGLOW

Prompt emission of GRB 121217A from gamma-rays to the near-infrared

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