Spectral Lags of Gamma-Ray Bursts From [ITAL]Ginga[/ITAL] and BATSE

Wu, Bobing; Fenimore, E. E.

doi:10.1086/312700

Cited by 48 publications

(53 citation statements)

References 17 publications

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“…We noticed, as did Wu & Fenimore (2000), that the lag extraction is sensitive to a number of parameters. Hence, in Table 3, we specify the band pass that we used to extract the lag, segment of the light curve used, temporal bin resolution, and the fitting range used in the CCF versus time delay plot.…”

Section: Resultsmentioning

confidence: 58%

SPECTRAL LAGS AND THE LAG-LUMINOSITY RELATION: AN INVESTIGATION WITHSWIFTBAT GAMMA-RAY BURSTS

Ukwatta

Stamatikos

Dhuga

et al. 2010

ApJ

131

137

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Spectral lag, the time difference between the arrival of high-energy and low-energy photons, is a common feature in gamma-ray bursts (GRBs). Norris et al. reported a correlation between the spectral lag and the isotropic peak luminosity of GRBs based on a limited sample. More recently, a number of authors have provided further support for this correlation using arbitrary energy bands of various instruments. In this paper, we report on a systematic extraction of spectral lags based on the largest Swift sample to date of 31 GRBs with measured redshifts. We extracted the spectral lags for all combinations of the standard Swift hard X-ray energy bands: 15-25 keV, 25-50 keV, 50-100 keV, and 100-200 keV and plotted the time dilation corrected lag as a function of isotropic peak luminosity. The mean value of the correlation coefficient for various channel combinations is −0.68 with a chance probability of ∼0.7 × 10 −3 . In addition, the mean value of the power-law index is 1.4 ± 0.3. Hence, our study lends support to the existence of a lag-luminosity correlation, albeit with large scatter.

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Section: Resultsmentioning

confidence: 58%

SPECTRAL LAGS AND THE LAG-LUMINOSITY RELATION: AN INVESTIGATION WITHSWIFTBAT GAMMA-RAY BURSTS

Ukwatta

Stamatikos

Dhuga

et al. 2010

ApJ

131

137

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show abstract

“…Indeed, Band et al (2004) argued for an empirical relation where E p is proportional to the square of the HR. Wu & Fenimore (2000) pointed out that it is not always reliable to determine lags with CCF. This is especially the case for multi-peaked bursts, for which both the HR and the CCF give an average quantitative description.…”

Section: Low Resolution Spectroscopy (Lrs)mentioning

confidence: 99%

“…Varying E 0 , η, and α between individual pulses will be important in determining the integrated spectrum, which is the spectrum that is quantified by the lags and the HRs. Wu & Fenimore (2000) also noted that the methods used to calculate the CCFs can affect the results considerably. For instance, the inclusion of time intervals when the signal is at background will clearly affect the measurements.…”

Section: Low Resolution Spectroscopy (Lrs)mentioning

confidence: 99%

Interpretations of gamma-ray burst spectroscopy

Ryde¹

2005

A&A

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Abstract. We describe the strong spectral evolution that occurs during a gamma-ray burst (GRB) pulse and the means by which it can be analyzed. In particular, we discuss the change of the light curve as a function of energy and the spectral lag. Based on observed empirical correlations, an analytical model is constructed which is used to describe the pulse shape and quantize the spectral lags and their dependences on the spectral evolution parameters. Using this model, we find that the spectral lag depends mainly on the pulse-decay time-scale and that hard spectra (with large spectral power-law indices α) give the largest lags. Similarly, large initial peak-energies, E 0 , lead to large lags, except in the case of very soft spectra. The hardness ratio is found to depend only weakly on α and the hardness-intensity-correlation index, η. In particular, for low E 0 , it is practically independent, and is determined mainly by E 0 . The relation between the hardness ratio and the lags, for a certain E 0 are described by power-laws, as α varies. These results are the consequences of the empirical description of the spectral evolution in pulses and can be used as a reference in analyses of observed pulses. We also discuss the expected signatures of a sample of hard spectral pulses (e.g. thermal or small pitch-angle synchrotron emission) versus soft spectral pulses (e.g. optically-thin synchrotron emission). Also the expected differences between a sample of low energetic bursts (such as X-ray flashes) and of high energetic bursts (classical bursts) are discussed.

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“…This assumption holds for a large region of the parameter space (KPS97 ;Piran 1999;Wu & Fenimore 2000). It may break down for large radii (where the shells' densities are low) or for small radii (where the shells may be optically thick).…”

Section: Introductionmentioning

confidence: 99%

Gamma-Ray Burst Light Curves—Another Clue on the Inner Engine

Nakar

Piran

2002

The Astrophysical Journal

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The nature of the inner engine that accelerates and collimates the relativistic flow at the cores of gamma-ray bursts (GRBs) is the most interesting current puzzle concerning GRBs. Numerical simulations have shown that the internal shocks' light curve reflects the activity of this inner engine. Using a simple analytic model, we clarify the relations between the observed gamma-ray light curve and the inner engine's activity and the dependence of the light curve on the inner engine's parameters. This simple model also explains the observed similarity between the observed distributions of pulses' widths and the interval between pulses, and the correlation between the width of a pulse and the duration of the preceding interval. Our analysis suggests that the variability in the wind's Lorentz factors arises because of a modulation of the mass injected into a constant energy flow.

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Spectral Lags of Gamma-Ray Bursts From [ITAL]Ginga[/ITAL] and BATSE

Cited by 48 publications

References 17 publications

SPECTRAL LAGS AND THE LAG-LUMINOSITY RELATION: AN INVESTIGATION WITHSWIFTBAT GAMMA-RAY BURSTS

SPECTRAL LAGS AND THE LAG-LUMINOSITY RELATION: AN INVESTIGATION WITHSWIFTBAT GAMMA-RAY BURSTS

Interpretations of gamma-ray burst spectroscopy

Gamma-Ray Burst Light Curves—Another Clue on the Inner Engine

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