Spectral characteristics of gamma-ray bursts observed by the anticoincidence shield of the SIGMA telescope aboard GRANAT

Pelaez, F.; Bouchet, L.; Jourdain, E.; Niel, M.; Claret, A.; Laurent, Philippe; Lebrun, F.; Paul, Jacques; Terekhov, O.; Sunyaev, R.; Kuznetsov, A.; Денисенко, Д.; Gilfanov, M.; Churazov, E.; Khavenson, N.; Diachkov, A.

doi:10.1086/192034

Cited by 7 publications

(3 citation statements)

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“…, and F p ∝ T −1 b . Evidence for a hardness-brightness correlation has been presented , Paciesas et al (1992), Nemiroff et al (1994), Pelaez et al (1994), and Mallozzi et al (1995), as it is implied by the hardness ratios, break energy or E p dependencies on the peak count rate or brightness class shown in these articles. A quantitative comparison is not easy as authors seldom use F p and E p in their analyses (or at least the same definition of the burst hardness); nevertheless it appears that the observed correlation is weaker than predicted above.…”

Section: Results and Comparison With Observational Datamentioning

confidence: 84%

Simulations of Gamma‐Ray Bursts from External Shocks: Time Variability and Spectral Correlations

Panaitescu

Mészáros

1998

ApJ

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We compute burst spectra and time structures arising from synchrotron and inverse Compton scattering by non-thermal electrons accelerated in shocks which form during the interaction between a thin ultra-relativistic fireball and a stationary external medium. We investigate the effect of varying the most important model parameters on the resulting burst spectra, and we present a set of correlations among the spectral and temporal features of the bursts. The spectral hardness, various spectral-temporal correlations and the spectral evolution of the simulated bursts are compared to those of observed bursts for a representative set of model parameters. Multi-pulse structures are simulated using a variable magnetic field and anisotropic emission, and the most important spectral and temporal properties of these pulses are compared with observations.

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Section: Results and Comparison With Observational Datamentioning

confidence: 84%

Simulations of Gamma‐Ray Bursts from External Shocks: Time Variability and Spectral Correlations

Panaitescu

Mészáros

1998

ApJ

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“…This is known as the synchrotron "line of death" (Preece et al 1998). An extra concern, is that the break observed at ν peak is often too sharp to be compatible with the smooth transition expected from the synchrotron model (Pelaez et al 1994).…”

Section: The Spectral Shapementioning

confidence: 98%

Constraints on the Synchrotron Emission Mechanism in Gamma-Ray Bursts

Beniamini

Piran

2013

ApJ

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We reexamine the general synchrotron model for GRBs' prompt emission and determine the regime in the parameter phase space in which it is viable. We characterize a typical GRB pulse in terms of its peak energy, peak flux and duration and use the latest Fermi observations to constrain the high energy part of the spectrum. We solve for the intrinsic parameters at the emission region and find the possible parameter phase space for synchrotron emission. Our approach is general and it does not depend on a specific energy dissipation mechanism. Reasonable synchrotron solutions are found with energy ratios of 10 −4 < B / e < 10, bulk Lorentz factor values of 300 < Γ < 3000, typical electrons' Lorentz factor values of 3 × 10 3 < γ e < 10 5 and emission radii of the order 10 15 cm < R < 10 17 cm. Most remarkable among those are the rather large values of the emission radius and the electron's Lorentz factor. We find that soft (with peak energy less than 100KeV) but luminous (isotropic luminosity of 1.5 × 10 53 ) pulses are inefficient. This may explain the lack of strong soft bursts. In cases when most of the energy is carried out by the kinetic energy of the flow, such as in the internal shocks, the synchrotron solution requires that only a small fraction of the electrons are accelerated to relativistic velocities by the shocks. We show that future observations of very high energy photons from GRBs by CTA, could possibly determine all parameters of the synchrotron model or rule it out altogether. situation concerning the prompt emission is more complicated.We characterize the conditions within the emitting region by six parameters: the co-moving magnetic field strength, B, the number of relativistic emitters, N e , the ratio between the magnetic energy and the internal energy of the electrons, ≡ B / e , the bulk Lorentz factor of the emitting region, Γ, the minimal electrons' Lorentz factor in the source frame, γ m and the ratio between the shell crossing time and the angular timescale, k. We then characterize a single, "typical", GRB pulse, which is the building block of the GRB lightcurve, by three basic quantities: the peak (sub-MeV) frequency, the peak flux and the duration. We compare the first two, the observed peak (sub-MeV) frequency and the peak flux with the predictions of the synchrotron model and we use the observed duration of the pulse to limit the angular time scale (Sari and Piran 1997a). The synchrotron solution is incomplete without a determination of the accompanying synchrotron self-Compton (SSC) emission, which influences the efficiency of the synchrotron emission. Furthermore, the observations of the high energy SSC emission poses additional constraints on the emitting region. We describe, therefore, a self-consistent synchrotron self-Compton solution.Three additional constraints should be taken into account (see also Daigne et al. 2011). First, energy considerations pose a strong lower limit on the efficiency. The energy of the observed sub-MeV flux, is huge and already highly constraining astrophy...

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“…The SIGMA telescope onboard the GRANAT satellite had an anti-coincidence shield of 8 CsI(Na) blocks, with each 4 cm thick block having a detection area of 0.15 m 2 (Paul et al 1990). In the years from 1990 to 1992, the active shield recorded high quality 200 keV-15 MeV energy spectra for 25 GRBs (Pelaez et al 1994). The OSSE instrument on the CGRO spacecraft also had a large shield composed of NaI scintillator that could be used to monitor GRBs.…”

Section: Introductionmentioning

confidence: 99%

Using the active collimator and shield assembly of an EXIST-type mission as a gamma-ray burst spectrometer

Garson

Krawczynski

Grindlay

et al. 2006

A&A

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The Energetic X-Ray Imaging Survey Telescope (EXIST) is a mission design concept that uses coded masks seen by Cadmium Zinc Telluride (CZT) detectors to register hard X-rays in the energy region from 10 keV to 600 keV. A partially active or fully active anticoincidence shield/collimator with a total area of between 15 m 2 and 35 m 2 will be used to define the field-of-view of the CZT detectors and to suppress the background of cosmic-ray-induced events. In this paper, we describe the use of a sodium activated cesium iodide shield/collimator to detect gamma-ray bursts (GRBs) and to measure their energy spectra in the energy range from 100 keV up to 10 MeV. We use the code GEANT 4 to simulate the interactions of photons and cosmic rays with the spacecraft and the instrument and the code DETECT2000 to simulate the optical properties of the scintillation detectors. The shield/collimator achieves a νF ν -sensitivity of 3 × 10 −9 erg cm −2 s −1 and 2 × 10 −8 erg cm −2 s −1 at 100 keV and 600 keV, respectively. The sensitivity is well matched to that of the coded mask telescope.The broad energy coverage of an EXIST-type mission with active shields will constrain the peak of the spectral energy distribution (SED) for a large number of GRBs. The measurement of the SED peak may be key for determining photometric GRB redshifts and for using GRBs as cosmological probes.

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Spectral characteristics of gamma-ray bursts observed by the anticoincidence shield of the SIGMA telescope aboard GRANAT

Cited by 7 publications

References 0 publications

Simulations of Gamma‐Ray Bursts from External Shocks: Time Variability and Spectral Correlations

Simulations of Gamma‐Ray Bursts from External Shocks: Time Variability and Spectral Correlations

Constraints on the Synchrotron Emission Mechanism in Gamma-Ray Bursts

Using the active collimator and shield assembly of an EXIST-type mission as a gamma-ray burst spectrometer

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