Minimum variability time-scales of long and short GRBs

MacLachlan, G. A.; Shenoy, A.; Сонбас, Э.; Dhuga, K. S.; Cobb, B. E.; Ukwatta, T. N.; Morris, David C.; Eskandarian, A.; Maximon, L. C.; Parke, William C.

doi:10.1093/mnras/stt241

Cited by 70 publications

(88 citation statements)

References 36 publications

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“…This finding is fully consistent with MacLachlan et al (2013), where it was also found (using a larger sample of short-duration GRBs) that the two histograms are quite broad and very similar in dispersion.…”

Section: Discussion and Resultssupporting

confidence: 91%

“…The ∆t min values in Figure 7 are bound from above by T 90 , and they do not strongly correlate with T 90 within the allowed region of the plot. Recently, MacLachlan et al (2013) have studied faint Fermi GBM GRBs and do find evidence for a correlation. We can reconcile our conclusions by identifying low SNR as the driving force in any apparent correlation.…”

Section: Discussion and Resultsmentioning

confidence: 99%

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Uncovering the Intrinsic Variability of Gamma-Ray Bursts

Golkhou

Butler

2014

ApJ

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We develop a robust technique to determine the minimum variability timescale for Gamma-ray Burst light curves, utilizing Haar wavelets. Our approach averages over the data for a given GRB, providing an aggregate measure of signal variation while also retaining sensitivity to narrow pulses within complicated time-series. In contrast to previous studies using wavelets, which simply define the minimum timescale in reference to the measurement noise floor, our approach identifies the signature of temporally-smooth features in the wavelet scaleogram and then additionally identifies a break in the scaleogram on longer timescales as signature of a true, temporally-unsmooth light curve feature or features. We apply our technique to the large sample of Swift GRB Gamma-ray light curves and for the first time -due to the presence of a large number of GRBs with measured redshift -determine the distribution of minimum variability timescales in the source frame. We find a median minimum timescale for long-duration GRBs in the source frame of ∆t min = 0.5 s, with the shortest timescale found being on the order of 10 ms. This short timescale suggests a compact central engine (3 × 10 3 km). We discuss further implications for the GRB fireball model and present a tantalizing correlation between minimum timescale and redshift, which may in part be due to cosmological time-dilation.

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Section: Discussion and Resultssupporting

confidence: 91%

Section: Discussion and Resultsmentioning

confidence: 99%

Uncovering the Intrinsic Variability of Gamma-Ray Bursts

Golkhou

Butler

2014

ApJ

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“…and Golkhou et al (2015) analyzed the MTS from the structurefunction method based on non-decimated Haar wavelets for a large sample of GRBs from Swif t and F ermi. They reported MTS values that are less dependent on the measurement noise level compared former works (e.g., Walker et al 2000;MacLachlan et al 2013;Sonbas et al 2014). Since this method get rid of artificial effect due top the noise floor, hereafter we adopt the MTS measurements reported in and Golkhou et al (2015).…”

Section: Samplementioning

confidence: 81%

“…The typical minimum variability timescale (MTS) for blazars is around one day (e.g., Vovk & Neronov 2013), where ultra-fast variability as short as 3-5 min at TeV energies is also found in some blazars (e.g., Aharonian et al 2007;Albert et al 2007;Aleksic et al 2014). The typical MTS of GRBs is around 0.5 s with the shortest timescale on the order of 10 ms (e.g., MacLachlan et al 2013;, where the MTS is much shorter than the overall duration (e.g., T90). The physical origin of the flux variation is unclear for both GRBs and blazars, where several models have been proposed to explain their temporal variability.…”

Section: Introductionmentioning

confidence: 99%

The extension of variability properties in gamma-ray bursts to blazars

Zhang

Lei

et al. 2015

Monthly Notices of the Royal Astronomical Society: Letters

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Both gamma-ray bursts (GRBs) and blazars have relativistic jets pointing at a small angle from our line of sight. Several recent studies suggested that these two kinds of sources may share similar jet physics. In this work, we explore the variability properties for GRBs and blazars as a whole. We find that the correlation between minimum variability timescale (MTS) and Lorentz factor, Γ, as found only in GRBs by Sonbas et al. can be extended to blazars with a joint correlation of MTS ∝ Γ −4.7±0.3 . The same applies to the MTS ∝ L −1.0±0.1 γ correlation as found in GRBs, which can be well extended into blazars as well. These results provide further evidence that the jets in these two kinds of sources are similar despite of the very different mass scale of their central engines. Further investigations of the physical origin of these correlations are needed, which can shed light on the nature of the jet physics.

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“…For short GRBs, the average dt is ≈10 −2 s (MacLachlan et al 2013). The detailed temporal structure of the gamma-ray lightcurve could not be determined by the GBM data for this weak event.…”

Section: Internal Shocksmentioning

confidence: 99%

Gravitational-Wave Observations May Constrain Gamma-Ray Burst Models: The Case of Gw150914–gbm

Vereš

Preece

Goldstein

et al. 2016

ApJL

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The possible short gamma-ray burst (GRB) observed by Fermi/GBM in coincidence with the first gravitationalwave (GW) detection offers new ways to test GRB prompt emission models. GW observations provide previously inaccessible physical parameters for the black hole central engine such as its horizon radius and rotation parameter. Using a minimum jet launching radius from the Advanced LIGO measurement of GW150914, we calculate photospheric and internal shock models and find that they are marginally inconsistent with the GBM data, but cannot be definitely ruled out. Dissipative photosphere models, however, have no problem explaining the observations. Based on the peak energy and the observed flux, we find that the external shock model gives a natural explanation, suggesting a low interstellar density (∼10 −3 cm −3 ) and a high Lorentz factor (∼2000). We only speculate on the exact nature of the system producing the gamma-rays, and study the parameter space of a generic Blandford-Znajek model. If future joint observations confirm the GW-short-GRB association we can provide similar but more detailed tests for prompt emission models.

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Minimum variability time-scales of long and short GRBs

Cited by 70 publications

References 36 publications

Uncovering the Intrinsic Variability of Gamma-Ray Bursts

Uncovering the Intrinsic Variability of Gamma-Ray Bursts

The extension of variability properties in gamma-ray bursts to blazars

Gravitational-Wave Observations May Constrain Gamma-Ray Burst Models: The Case of Gw150914–gbm

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