Detection of a Thermal Spectral Component in the Prompt Emission of GRB 100724b

Guiriec, S.; Connaughton, V.; Briggs, M. S.; Burgess, J. Michael; Ryde, F.; Daigne, F.; Mészáros, P.; Goldstein, A.; McEnery, J. E.; Omodei, N.; Bhat, P. N.; Bissaldi, E.; Camero-Arranz, A.; Chaplin, V.; Diehl, R.; Fishman, G. J.; Foley, S.; Gibby, M. H.; Giles, M. M.; Greiner, J.; Gruber, D.; Kienlin, A. von; Kippen, M.; Kouveliotou, C.; McBreen, S.; Meegan, C.; Pačiesas, W. S.; Preece, R.; Rau, A.; Tierney, D.; Horst, A. J. van der; Wilson-Hodge, C.

doi:10.1088/2041-8205/727/2/l33

Cited by 243 publications

(313 citation statements)

References 28 publications

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“…However recent GRB studies with Fermi have suggested that there are a number of GRBs whose spectral behaviour differs from a Band function, with a number of different spectral components invoked in order to explain these observations (e.g. Asano et al 2009;Burgess et al 2011;Guiriec et al 2011;Pe'er et al 2012). The Fermi data cover a wide energy band with high spectral resolution and so the systematic study of low-energy spectral deviations in bright Fermi bursts presented here enables the frequency of such events to be investigated.…”

Section: Discussionmentioning

confidence: 94%

“…The prompt emission of GRBs has been detected over a wide spectral range from keV to GeV energies and is generally well modelled by one or a combination of the following: a smoothly broken power-law (e.g. Band et al 1993;Abdo et al 2009b), a quasi-thermal component (e.g., Preece 2000; Guiriec et al 2011;Ryde et al 2011;Axelsson et al 2012), an extra nonthermal power-law component extending to high energies (e.g. González et al 2003;Kaneko et al 2008;Abdo et al 2009a) or a cut-off in the MeV regime (e.g., Ackermann et al 2012b).…”

Section: Introductionmentioning

confidence: 99%

“…A number of papers discuss interesting bursts with unusual spectral behaviour in the keV range (e.g., Guiriec et al 2011;Ryde et al 2011;Axelsson et al 2012). It is important to note that there is a bias in the literature whereby interesting bursts are published more than bursts that conform to the standard GRB models.…”

Section: Introductionmentioning

confidence: 99%

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Anomalies in low-energy gamma-ray burst spectra with theFermiGamma-ray Burst Monitor

Tierney

McBreen

Preece

et al. 2013

A&A

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Context. A Band function has become the standard spectral function used to describe the prompt emission spectra of gamma-ray bursts (GRBs). However, deviations from this function have previously been observed in GRBs detected by BATSE and in individual GRBs from the Fermi era. Aims. We present a systematic and rigorous search for spectral deviations from a Band function at low energies in a sample of the first two years of high fluence, long bursts detected by the Fermi Gamma-ray Burst Monitor (GBM). The sample contains 45 bursts with a fluence greater than 2 × 10 −5 erg/cm 2 (10−1000 keV).Methods. An extrapolated fit method is used to search for low-energy spectral anomalies, whereby a Band function is fit above a variable low-energy threshold and then the best fit function is extrapolated to lower energy data. Deviations are quantified by examining residuals derived from the extrapolated function and the data and their significance is determined via comprehensive simulations which account for the instrument response. This method was employed for both time-integrated burst spectra and time-resolved bins defined by a signal-to-noise ratio of 25σ and 50σ. Results. Significant deviations are evident in 3 bursts (GRB 081215A, GRB 090424 and GRB 090902B) in the time-integrated sample (∼7%) and 5 bursts (GRB 090323, GRB 090424, GRB 090820, GRB 090902B and GRB 090926A) in the time-resolved sample (∼11%). Conclusions. The advantage of the systematic, blind search analysis is that it can demonstrate the requirement for an additional spectral component without any prior knowledge of the nature of that extra component. Deviations are found in a large fraction of high fluence GRBs; fainter GRBs may not have sufficient statistics for deviations to be found using this method.

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Section: Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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Anomalies in low-energy gamma-ray burst spectra with theFermiGamma-ray Burst Monitor

Tierney

McBreen

Preece

et al. 2013

A&A

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“…The energy spectrum is highly non-thermal and is usually described empirically by the Band function (Band et al 1993), a smoothly joined broken power-law whose νF ν spectrum peaks at E p of a few hundred keV (Preece et al 2000;Kaneko et al 2006;Guidorzi et al 2011;Goldstein et al 2012;Gruber et al 2014;Bošnjak et al 2014), in some cases accompanied by a mostly subdominant thermal component (e.g. Guiriec et al 2011Guiriec et al , 2015; see Pe'er 2015 for a review). An ultra-relativistic outflow (with Lorentz factor Γ of a few 10 2 ) is required to reduce the pair production Full Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/589/A97 opacity and explain why a non-thermal spectrum extending to the MeV and GeV ranges is observed (e.g.…”

Section: Introductionmentioning

confidence: 99%

Correlation between peak energy and Fourier power density spectrum slope in gamma-ray bursts

Dichiara

Guidorzi

Amati

et al. 2016

A&A

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Context. The origin of the gamma-ray burst (GRB) prompt emission still defies explanation, in spite of recent progress made, for example, on the occasional presence of a thermal component in the spectrum along with the ubiquitous non-thermal component that is modelled with a Band function. The combination of finite duration and aperiodic modulations make GRBs hard to characterise temporally. Although correlations between GRB luminosity and spectral hardness on one side and time variability on the other side have long been known, the loose and often arbitrary definition of the latter makes the interpretation uncertain. Aims. We characterise the temporal variability in an objective way and search for a connection with rest-frame spectral properties for a number of well-observed GRBs. Methods. We studied the individual power density spectra (PDS) of 123 long GRBs with measured redshift, rest-frame peak energy E p,i of the time-averaged ν F ν spectrum, and well-constrained PDS slope α detected with Swift, Fermi and past spacecraft. The PDS were modelled with a power law either with or without a break adopting a Bayesian Markov chain Monte Carlo technique. Results. We find a highly significant E p,i -α anti-correlation. The null hypothesis probability is ∼10 −9 . Conclusions. In the framework of the internal shock synchrotron model, the E p,i -α anti-correlation can hardly be reconciled with the predicted E p,i ∝ Γ −2 , unless either variable microphysical parameters of the shocks or continual electron acceleration are assumed. Alternatively, in the context of models based on magnetic reconnection, the PDS slope and E p,i are linked to the ejecta magnetisation at the dissipation site, so that more magnetised outflows would produce more variable GRB light curves at short timescales ( 1 s), shallower PDS, and higher values of E p,i .

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“…Determinations of coefficients a and b of correlations could tell us whether these empirical luminosity correlations are independent on the redshift, which is very crucial for treating GRB as the distance indicator to investigate the evolution of our Universe. In addition, some new models for GRB have been proposed in resent years, such as the spectro-temporal multicomponent model (Guiriec et al 2011(Guiriec et al , 2013(Guiriec et al , 2015a(Guiriec et al ,b, 2016a. Interestingly, this model could result in a new time-resolved relation: the relation between the luminosity of the non-thermal component, L nTH i…”

Section: Introductionmentioning

confidence: 99%

Evolutions and Calibrations of Long Gamma-Ray-burst Luminosity Correlations Revisited

Wang

et al. 2017

ApJ

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Luminosity correlations of long Gamma-ray bursts (GRB) are extensively proposed as an effective complementarity to trace the Hubble diagram of Universe at high redshifts, which is of great importance to explore properties of dark energy. Recently, several empirical luminosity correlations have been statistically proposed from GRB observations. However, to treat GRB as the distance indicator, there are two key issues: the redshift evolution of luminosity correlations and their calibrations. In this paper, we choose the Amati relation, the correlation between the peak spectra energy and the equivalent isotropic energy of GRBs (E p − E iso ), as an example, and find that the current GRB dataset implies that there could be a evolution of the luminosity correlation with respect to the redshift. Therefore, we propose an extended Amati relation with two extra redshift-dependent terms to correct the redshift evolution of GRB relation. Secondly, we carefully check the reliability of the calibration method using the low-redshift GRB data. Importantly, we find that the low-redshift calibration method does not take whole correlations between Ω m and coefficients into account. Neglecting these correlation information can break the degeneracies and obtain the biased constraint on Ω m which is very sensitive to values of parameters for the calibration. A small shift of parameters of "calibrated" relation could significantly change the final constraint on Ω m in the low-redshift calibration method. Finally, we simulate several GRB samples with different statistical errors and find that, in order to correctly recover the fiducial value of Ω m using the low-redshift calibration method, we need a large number of GRB samples with high precisions.

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Detection of a Thermal Spectral Component in the Prompt Emission of GRB 100724b

Cited by 243 publications

References 28 publications

Anomalies in low-energy gamma-ray burst spectra with theFermiGamma-ray Burst Monitor

Anomalies in low-energy gamma-ray burst spectra with theFermiGamma-ray Burst Monitor

Correlation between peak energy and Fourier power density spectrum slope in gamma-ray bursts

Evolutions and Calibrations of Long Gamma-Ray-burst Luminosity Correlations Revisited

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