The Connection between Spectral Evolution and Gamma‐Ray Burst Lag

Kocevski, D.; Liang, Edison

doi:10.1086/376868

Cited by 61 publications

(55 citation statements)

References 12 publications

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“…There is a hard-to-soft evolution which is represented also in the evolution from higher to lower E peak of the three emission episodes. A similar behavior is seen in other long GRBs (Kocevski & Liang 2003;Hafizi & Mochkovitch 2007). It is interesting to note that the overall HR-evolution over the burst duration is much larger than the canonical HR-intensity correlation between the 3 emission episodes -see the particularly soft HR of episode III despite its high intensity.…”

Section: Episode IIIsupporting

confidence: 76%

Fermi/GBM observations of the ultra-long GRB 091024

Gruber

Krühler

Foley

et al. 2011

A&A

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Aims. In this paper we examine gamma-ray and optical data of GRB 091024, a gamma-ray burst (GRB) with an extremely long duration of T 90 ≈ 1020 s, as observed with the Fermi Gamma-ray Burst Monitor (GBM). Methods. We present spectral analysis of all three distinct emission episodes using data from Fermi/GBM. Because of the long nature of this event, many ground-based optical telescopes slewed to its location within a few minutes and thus were able to observe the GRB during its active period. We compare the optical and gamma-ray light curves. Furthermore, we estimate a lower limit on the bulk Lorentz factor from the variability and spectrum of the GBM light curve and compare it with that obtained from the peak time of the forward shock of the optical afterglow. Results. From the spectral analysis we note that, despite its unusually long duration, this burst is similar to other long GRBs, i.e. there is spectral evolution (both the peak energy and the spectral index vary with time) and spectral lags are measured. We find that the optical light curve is highly anti-correlated to the prompt gamma-ray emission, with the optical emission reaching the maximum during an epoch of quiescence in the prompt emission. We interpret this behavior as the reverse shock (optical flash), expected in the internal-external shock model of GRB emission but observed only in a handful of GRBs so far. The lower limit on the initial Lorentz factor deduced from the variability time scale (Γ min = 195 +90 −110 ) is consistent within the error to the one obtained using the peak time of the forward shock (Γ 0 = 120) and is also consistent with Lorentz factors of other long GRBs.

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Section: Episode IIIsupporting

confidence: 76%

Fermi/GBM observations of the ultra-long GRB 091024

Gruber

Krühler

Foley

et al. 2011

A&A

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“…In the case of the spectral-lag-luminosity relation, one possible explanation for the observed lags involves the spectral evolution during the prompt phase (Dermer 1998;Kocevski & Liang 2003;Ryde 2005) in which, due to cooling effects, E pk shifts toward a lower energy band so that the temporal peak of the corresponding light curve will also shift to lower energies, thereby resulting in the observed lag. Another explanation for the spectral-lag-luminosity relation is based purely on kinematic effects (Salmonson 2000;Salmonson & Galama 2002;Ioka & Nakamura 2001;Dermer 2004;Shen et al 2005;Lu et al 2006), where the peak luminosity L pk and spectral lag τ depend on a single kinematic variable…”

Section: Discussionmentioning

confidence: 99%

Luminosity Correlations for Gamma-Ray Bursts and Implications for Their Prompt and Afterglow Emission Mechanisms

Sultana

Kazanas

Fukumura

2012

ApJ

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We present the relation between the (z-and k-corrected) spectral lags, τ , for the standard Swift energy bands 50-100 keV and 100-200 keV and the peak isotropic luminosity, L iso (a relation reported first by Norris et al.), for a subset of 12 long Swift gamma-ray bursts (GRBs) taken from a recent study of this relation by Ukwatta et al. The chosen GRBs are also a subset of the Dainotti et al. sample, a set of Swift GRBs of known redshift, employed in establishing a relation between the (GRB frame) luminosity, L X , of the shallow (or constant) flux portion of the typical X-Ray Telescope GRB-afterglow light curve and the (GRB frame) time of transition to the normal decay rate, T brk . We also present the L X -T brk relation using only the bursts common in the two samples. The two relations exhibit a significant degree of correlation (ρ = −0.65 for the L iso -τ and ρ = −0.88 for the L X -T brk relation) and have surprisingly similar best-fit power-law indices (−1.19 ± 0.17 for L iso -τ and −1.10 ± 0.03 for L X -T brk ). Even more surprisingly, we noted that although τ and T brk represent different GRB time variables, it appears that the first relation (L iso -τ ) extrapolates into the second one for timescales τ T brk . This fact suggests that these two relations have a common origin, which we conjecture to be kinematic. This relation adds to the recently discovered relations between properties of the prompt and afterglow GRB phases, indicating a much more intimate relation between these two phases than hitherto considered.

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“…The time profile of gamma-ray bursts appear to display high-energy band emission preceding the arrival of photons to low-energy bands. This observed lag between the bands is a direct consequence of the spectral evolution of GRBs, where the peak energy of the spectrum decays with time (Kocevski & Liang 2003;Gehrels et al 2006;Norris & Bonnell 2006). It has been noted that the distribution of these lags is different for short and long bursts (Yi et al 2006;Foley et al 2009).…”

Section: Spectral Lagsmentioning

confidence: 99%

Searching for differences inSwift’s intermediate GRBs

Postigo

Horváth²,

Vereš

et al. 2010

A&A

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Context. Gamma-ray bursts are usually classified in terms their high-energy emission into either short-duration or long-duration bursts, which presumably reflect two different types of progenitors. However, it has been shown on statistical grounds that a third, intermediate population is needed in this classification scheme, although an extensive study of the properties of this class has so far not been performed. The large amount of follow-up studies generated during the Swift era allows us to have a sufficient sample to attempt a study of this third population through the properties of their prompt emission and their afterglows. Aims. To understand the differences of the intermediate population, we study a sample of GRBs observed by Swift during its first four years of operation. The sample contains only bursts with measured redshifts since these data help us to derive intrinsic properties. Methods. We search for differences in the properties of the three groups of bursts, which we quantify using a Kolmogorov-Smirnov test whenever possible. Results. Intermediate bursts are found to be less energetic and have dimmer afterglows than long GRBs, especially when considering the X-ray light curves, which are on average one order of magnitude fainter than long bursts. There is a less significant trend in the redshift distribution that places intermediate bursts closer than long bursts. Except for this, intermediate bursts show similar properties to long bursts. In particular, they follow the E peak versus E iso correlation and have, on average, positive spectral lags with a distribution similar to that of long bursts. As for long GRBs, they normally have an associated supernova, although some intermediate bursts have been found to contain no supernova component. Conclusions. This study shows that intermediate bursts differ from short bursts, but exhibit no significant differences from long bursts apart from their lower brightness. We suggest that the physical difference between intermediate and long bursts could be explained by being produced by similar progenitors, of the former being the ejecta thin shells and the latter thick shells.

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The Connection between Spectral Evolution and Gamma‐Ray Burst Lag

Cited by 61 publications

References 12 publications

Fermi/GBM observations of the ultra-long GRB 091024

Fermi/GBM observations of the ultra-long GRB 091024

Luminosity Correlations for Gamma-Ray Bursts and Implications for Their Prompt and Afterglow Emission Mechanisms

Searching for differences inSwift’s intermediate GRBs

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