BATSE observations of gamma-ray burst spectra. 2: Peak energy evolution in bright, long bursts

Ford, L.; Band, D. L.; Matteson, J. L.; Briggs, M. S.; Pendleton, G. N.; Preece, R. D.; Pačiesas, W. S.; Teegarden, B. J.; Palmer, D. M.; Schaefer, Bradley E.; Cline, T. L.; Fishman, G. J.; Kouveliotou, C.; Meegan, C.; Wilson, R. B.; Lestrade, John Patrick

doi:10.1086/175174

Cited by 238 publications

(226 citation statements)

References 14 publications

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“…The observed spectral behaviour is entirely consistent with the gamma-ray spectral evolution seen in BATSE GRBs (e.g. Ford et al 1995;Bhat et al 1994). …”

Section: Spectral Characteristics Of the Early X-ray Light-curvesupporting

confidence: 82%

Swift multi-wavelength observations of the bright flaring burst GRB 051117A

Goad

Page

Godet

et al. 2007

A&A

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We report on the temporal and spectral characteristics of the early X-ray emission from the Gamma Ray Burst 051117A as observed by Swift. The superb quality of the early X-ray light-curve and spectra of this source, one of the brightest seen by the X-ray Telescope at such early times, allows an unprecedented look at the spectral and temporal evolution of the prompt and early afterglow emission for this GRB and allows us to place stringent limits on the detection of lines. GRB 051117A displays a highly complex light-curve, with an apparent initial slow decline of slope α = 0.77 ± 0.07 ( f (t) ∝ t −α ) dominated by numerous superposed flares of varying amplitude and duration. Between orbits 2 and 3, the X-ray light-curve drops abruptly, highlighting the dominance of flaring activity at early times, and indicating that the central engine for this burst remains active for several kiloseconds after the initial explosion. The late time slope (t > 10 4 s) also decays relatively slowly with a powerlaw index of α = 0.66, breaking to a steeper slope of 1.1, 170 ks after the BAT trigger. The X-ray light-curve at early times is characteristic of a noise process, consisting of random shots superposed on an underlying powerlaw decay, with individual shots well-modelled by a fast-rise and exponential decay spanning a broad range in rise-times and decay rates. A temporal spectral analysis of the early light-curve shows that the photon index and source intensity are highly correlated with the spectrum being significantly harder when brighter, consistent with the movement of the peak of the Band function to lower energies following individual flares. The high quality spectrum obtained from the first orbit of WT mode data, enables us to place a 3σ upper limit on the strength of any emission line features of EW < 15 eV, assuming a narrow emission-line of 100 eV at the peak of the effective area.

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“…The observed spectral behaviour is entirely consistent with the gamma-ray spectral evolution seen in BATSE GRBs (e.g. Ford et al 1995;Bhat et al 1994). …”

Section: Spectral Characteristics Of the Early X-ray Light-curvesupporting

confidence: 82%

Swift multi-wavelength observations of the bright flaring burst GRB 051117A

Goad

Page

Godet

et al. 2007

A&A

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“…The best fit parameters were then examined in search for any indetermination: when at least 3 subsequent spectra had one or more undetermined spectral parameter, the spectra were grouped according to a S /N criterion. We followed the prescriptions of Preece et al (2000) who accumulate subsequent HERB spectra until the S /N (calculated for the 28-1800 keV energy range) is greater than 45; for the SHERB data the S /N threshold was fixed at 15 as already done by Ford et al (1995). If after this accumulation the number of time resolved spectra was less than 5 the burst was not included in the final list of analyzed events (see Sect.…”

Section: Spectral Analysismentioning

confidence: 99%

“…This empirical model (BAND hereafter) was first proposed by Band et al (1993) and, as already mentioned, is a good general and simple description of the time averaged (Band et al 1993) and the time resolved spectra (Ford et al 1995;Preece et al 1998). It contains the two continuum components in the keVMeV band already discovered before BATSE: (i) a low energy power law with an exponential cutoff N(E) ∝ E α exp(−E/E 0 ) and (ii) a high energy power law N(E) ∝ E β (Matz et al 1985).…”

Section: The Band Modelmentioning

confidence: 99%

Time resolved spectral analysis of bright gamma ray bursts

Ghirlanda

Celotti

Ghisellini

2002

A&A

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Abstract. We present the time integrated and time resolved spectral analysis of a sample of bright bursts selected with F peak ≥ 20 phot cm −2 s −1 from the BATSE archive. We fitted four different spectral models to the pulse time integrated and time resolved spectra. We compare the low energy slope of the fitted spectra with the prediction of the synchrotron theory [predicting photon spectra softer than N(E) ∝ E −2/3 ], and test, through direct spectral fitting, the synchrotron shock model. We point out that differences in the parameters distribution can be ascribed to the different spectral shape of the models employed and that in most cases the spectrum can be described by a smoothly curved function. The synchrotron shock model does not give satisfactory fits to the time averaged and time resolved spectra. Finally, we derive that the synchrotron low energy limit is violated in a considerable number of spectra both during the rise and decay phase around the peak.

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“…dominated by one main pulse or made of just a few pulses) while in complex bursts with many pulses only the correlation between hardness and count rate is clearly visible. Also, the hardness of successive pulses remains essentially correlated to the intensity instead of decreasing like in 50% of the Ford et al (1995) sample.…”

Section: Instantaneous Hardnessmentioning

confidence: 96%

“…We encountered more difficulties with the global hard-to-soft evolution which was observed in 70% of the sample of bright long bursts studied by Ford et al (1995). In synthetic bursts (Fig.10) it is present as long as the profiles remain relatively simple (i.e.…”

Section: Instantaneous Hardnessmentioning

confidence: 97%

Gamma-ray bursts from internal shocks in a relativistic wind: Temporal and spectral properties

Mochkovitch¹,

Fuchs²

1996

AIP Conference Proceedings

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We construct models for gamma-ray bursts where the emission comes from internal shocks in a relativistic wind with a highly non uniform distribution of the Lorentz factor. We follow the evolution of the wind using a very simplified approach where a large number of layers interact by direct collisions but where all pressure waves have been suppressed. We suppose that the magnetic field and the electron Lorentz factor reach large equipartition values in the shocks. Synchrotron photons emitted by the relativistic electrons have a typical energy in the gamma-ray range in the observer frame. Synthetic bursts are constructed as the sum of the contributions from all the internal elementary shocks and their temporal and spectral properties are compared to the observations. We reproduce the diversity of burst profiles, the "FRED" shape of individual pulses and the short time scale variability. Synthetic bursts also satisfy the duration-hardness relation and individual pulses are found to be narrower at high energy, in agreement with the observations. These results suggest that internal shocks in a relativistic wind may indeed be at the origin of gamma-ray bursts. A potential problem is however the relatively low efficiency of the dissipation process. If the relativistic wind is powered by accretion from a disc to a stellar mass black hole it implies that a substantial fraction of the available energy is injected into the wind.

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BATSE observations of gamma-ray burst spectra. 2: Peak energy evolution in bright, long bursts

Cited by 238 publications

References 14 publications

Swift multi-wavelength observations of the bright flaring burst GRB 051117A

Swift multi-wavelength observations of the bright flaring burst GRB 051117A

Time resolved spectral analysis of bright gamma ray bursts

Gamma-ray bursts from internal shocks in a relativistic wind: Temporal and spectral properties

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