scholarly journals CORRELATION BETWEEN HARDNESS RATIO AND DURATION OF FERMI GAMMA-RAY BURSTS

2013 ◽  
Vol 23 ◽  
pp. 298-300
Author(s):  
FU-WEN ZHANG
Keyword(s):  
Statistical Analysis ◽  
Power Law ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Spectral Shape ◽  
Energy Bands ◽  
Hardness Ratio

Using the latest gamma-ray bursts (GRB) observed by Fermi-GBM, we perform a statistical analysis of the relation between hardness ratio (HR) and duration (ΔT) of GRBs, and find that HR and ΔT are still anti-correlated. we also find that this correlation strongly depends upon the spectral shape of GRBs and energy bands, and the bursts with the curved spectra in the typical BATSE energy bands show a tighter anti-correlation than those with the power-law spectra in the typical BAT energy bands. This might explain why the HR – ΔT correlation is not evident for Swift-BAT GRB sample as well as other GRB sample detected by instruments with a narrower/softer energy bandpass such as HETE-2.

scholarly journals In Vacuo Dispersion-Like Spectral Lags in Gamma-Ray Bursts

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 541
Author(s):  
Giovanni Amelino-Camelia ◽  
Giacomo D’Amico ◽  
Fabrizio Fiore ◽  
Simonetta Puccetti ◽  
Michele Ronco
Keyword(s):  
Statistical Analysis ◽  
Linear Correlation ◽  
Gamma Ray ◽  
Statistical Evidence ◽  
Gamma Ray Bursts ◽  
Quantum Geometry

Some recent studies exposed preliminary but rather intriguing statistical evidence of in vacuo dispersion-like spectral lags for gamma-ray bursts (GRBs), a linear correlation between time of observation and energy of GRB particles, which is expected in some models of quantum geometry. Those results focused on testing in vacuo dispersion for the most energetic GRB particles, and in particular only included photons with energy at emission greater than 40 GeV. We here extend the window of the statistical analysis down to 5 GeV and find results that are consistent with what had been previously noticed at higher energies.

scholarly journals Optical Afterglows as Probes for the Central Engine and Fireball of Gamma-Ray Bursts

2012 ◽  
Vol 8 (S290) ◽  
pp. 263-264
Author(s):  
Liang Li ◽  
En-Wei Liang ◽  
He Gao ◽  
Bing Zhang
Keyword(s):  
Statistical Analysis ◽  
Gamma Rays ◽  
Density Profile ◽  
Gamma Ray ◽  
Ambient Medium ◽  
Gamma Ray Bursts ◽  
Prompt Gamma ◽  
Medium Density ◽  
Central Engine ◽  
Prompt Emission

AbstractWell-sampled optical lightcurves of 146 gamma-ray bursts (GRBs) are compiled from literature. We identify possible emission components based on our empirical fits and present statistical analysis for these components. We find that the flares are related to prompt emission, suggesting that they could have the same origin in different episodes. The shallow decay segment is not correlated with prompt gamma-rays. It likely signals a long-lasting injected wind from GRB central engines. Early after onset peak is closely related with prompt emission. The ambient medium density profile is likely n ∝ r−1. No correlation between the late re-brightening bump and prompt gamma-rays or the onset bump is found. They may be from another jet component.

Precursors of short gamma-ray bursts detected by the INTEGRAL observatory

2018 ◽  
Vol 27 (10) ◽  
pp. 1844013 ◽  
Author(s):  
Pavel Minaev ◽  
Alexei Pozanenko ◽  
Sergei Molkov
Keyword(s):  
Statistical Analysis ◽  
Light Curve ◽  
Relative Intensity ◽  
Gamma Ray ◽  
Convincing Evidence ◽  
Gamma Ray Bursts ◽  
Light Curves ◽  
Upper Limits ◽  
Short Grbs

We have analyzed the light curves of 527 short gamma-ray bursts (GRBs) registered by the SPI-ACS, SPI and IBIS/ISGRI experiments of INTEGRAL observatory totally to search for precursors. Both the light curves of each 527 individual burst and the averaged light curve of 372 brightest SPI-ACS bursts have been analyzed. In a few cases, we have found and investigated precursor candidates using SPI-ACS, SPI and IBIS/ISGRI of INTEGRAL, GBM and LAT of Fermi data. No convincing evidence for the existence of precursors of short GRBs has been found. A statistical analysis of the averaged light curve for the sample of brightest short bursts has revealed no regular precursor. Upper limits for the relative intensity of precursors have been estimated. We show that the fraction of short GRBs with precursors is less than 0.4% of all short bursts, detected by INTEGRAL.

scholarly journals Spectral properties of gamma-ray bursts observed by the Suzaku wide-band all-sky monitor

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Norisuke Ohmori ◽  
Kazutaka Yamaoka ◽  
Makoto Yamauchi ◽  
Yuji Urata ◽  
Masanori Ohno ◽  
...  
Keyword(s):  
Short Duration ◽  
Power Law ◽  
Spectral Properties ◽  
Gamma Ray ◽  
Wide Band ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Sky Monitor ◽  
S Peak ◽  
Single Power

Abstract We have systematically studied the spectral properties of 302 localized gamma-ray bursts (GRBs) observed by the Suzaku wide-band all-sky monitor (WAM) from 2005 August to 2010 December. The energy spectra in the 100–5000 keV range integrated over the entire emission and the 1 s peak were fitted by three models: a single power law, a power law with an exponential cutoff (CPL), and the GRB Band function (GRB). Most of the burst spectra were well fitted by a single power law. The average photon index α was −2.11 and −1.73 for long and short bursts, respectively. For the CPL and GRB models, the low-energy and high-energy photon indices (α and β) for the entire emission spectra were consistent with previous measurements. The averages of the α and β were −0.90 and −2.65 for long-duration GRBs, while the average α was −0.55 and the β was not well constrained for short-duration GRBs. However, the average peak energy Epeak was 645 and 1286 keV for long- and short-duration GRBs respectively, which are higher than previous Fermi/GBM measurements (285 keV and 736 keV). The α and Epeak of the 1 s peak spectra were larger, i.e., the spectra were harder, than the total fluence spectra. Spectral simulations based on Fermi-GBM results suggest that the higher Epeaks measured by the Suzaku WAM could be due to detector selection bias, mainly caused by the limited energy range above 100 keV.

scholarly journals Study on the escape timescale of high-energy particles from supernova remnants through thermal X-ray properties

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Hiromasa Suzuki ◽  
Aya Bamba ◽  
Ryo Yamazaki ◽  
Yutaka Ohira
Keyword(s):  
Power Law ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
High Energy ◽  
Spectral Shape ◽  
X Ray ◽  
Galactic Cosmic Ray ◽  
High Energy Particles ◽  
Accelerated Particles

Abstract In the current decade, GeV/TeV gamma-ray observations of several supernova remnants (SNRs) have implied that accelerated particles are escaping from their acceleration sites. However, when and how they escape from the SNR vicinities are yet to be understood. Recent studies have suggested that the particle escape might develop with thermal plasma ages of the SNRs. We present a systematic study on the time evolution of particle escape using thermal X-ray properties and gamma-ray spectra using 38 SNRs associated with GeV/TeV gamma-ray emissions. We conducted spectral fittings on the gamma-ray spectra using exponential cutoff power-law and broken power-law models to estimate the exponential cutoff or the break energies, both of which are indicators of particle escape. Plots of the gamma-ray cutoff/break energies over the plasma ages show similar tendencies to those predicted by analytical/numerical calculations of particle escape under conditions in which a shock is interacting with thin interstellar medium or clouds. The particle escape timescale is estimated as ∼100 kyr from the decreasing trends of the total energy of the confined protons with the plasma age. The large dispersions of the cutoff/break energies in the data may suggest an intrinsic variety of particle escape environments. This might be the cause of the complicated Galactic cosmic ray spectral shape measured on Earth.

scholarly journals Luminosity Distribution of Gamma-ray Burst Optical Afterglows

2012 ◽  
Vol 8 (S290) ◽  
pp. 335-336
Author(s):  
X. G. Wang ◽  
E. W. Liang ◽  
L. Li ◽  
J. J. Wei ◽  
B. Zhang
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Power Law ◽  
Luminosity Function ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Gamma Ray Burst

AbstractWe derive the optical afterglow luminosity distributions at different epoches for gamma-ray bursts (GRBs) from a sample of 146 GRBs that have a well-sampled optical afterglow lightcurve, then explore the luminosity function of GRB optical afterglows using the Monte Carlo simulation. We show that an intrinsic broken power-law luminosity function can well reproduced the observed magnitude distributions.

Sign in / Sign up

Export Citation Format

Share Document