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181. GRB spectral properties from Fermi and Swift
ID:
ivo://CDS.VizieR/J/ApJ/898/14
Title:
GRB spectral properties from Fermi and Swift
Short Name:
J/ApJ/898/14
Date:
21 Mar 2022 07:04:24
Publisher:
CDS
Description:
We statistically examine the gamma-ray burst (GRB) photon indices obtained by the Fermi-GBM and Fermi-LAT observations and compare the LAT GRB photon indices to the GBM GRB photon indices. We apply the jitter radiation to explain the GRB spectral diversities in the high-energy bands. In our model, the jitter radiative spectral index is determined by the spectral index of the turbulence. We classify GRBs into three classes depending on the shape of the GRB high-energy spectrum when we compare the GBM and LAT detections: the GRB spectrum is concave (GRBs turn out to be softer and are labeled as S-GRBs), the GRB spectrum is convex (GRBs turn out to be harder and are labeled as H-GRBs), and the GRBs have no strong spectral changes (labeled as N-GRBs). A universal Kolmogorov index 7/3 in the turbulent cascade is consistent with the photon index of the N-GRBs. The S-GRB spectra can be explained by the turbulent cascade due to the kinetic magnetic reconnection with the spectral index range of the turbulence from 8/3 to 3.0. The H-GRB spectra originate from the inverse turbulent cascade with the spectral index range of the turbulence from 2.0 to 3.5 that occurred during the large lengthscale magnetic reconnection. Thus, the GRB radiative spectra are diversified because the turbulent cascade modifies the turbulent energy spectrum. More observational samples are expected in the future to further identify our suggestions.
182. GRB Swift X-ray light curves analysis
ID:
ivo://CDS.VizieR/J/MNRAS/428/729
Title:
GRB Swift X-ray light curves analysis
Short Name:
J/MNRAS/428/729
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a comprehensive statistical analysis of Swift X-ray light curves of gamma-ray bursts (GRBs) collecting data from more than 650 GRBs discovered by Swift and other facilities. The unprecedented sample size allows us to constrain the rest-frame X-ray properties of GRBs from a statistical perspective, with particular reference to intrinsic time-scales and the energetics of the different light-curve phases in a common rest-frame 0.3-30keV energy band. Temporal variability episodes are also studied and their properties constrained. Two fundamental questions drive this effort: (i) Does the X-ray emission retain any kind of 'memory' of the prompt {gamma}-ray phase? (ii) Where is the dividing line between long and short GRB X-ray properties? We show that short GRBs decay faster, are less luminous and less energetic than long GRBs in the X-rays, but are interestingly characterized by similar intrinsic absorption. We furthermore reveal the existence of a number of statistically significant relations that link the X-ray to prompt {gamma}-ray parameters in long GRBs; short GRBs are outliers of the majority of these two-parameter relations. However and more importantly, we report on the existence of a universal three-parameter scaling that links the X-ray and the {gamma}-ray energy to the prompt spectral peak energy of both long and short GRBs: E_X,iso_{prop.to}E^1.00+/-0.06^_{gamma},iso_/E^0.60+/-0.10^_pk_.
183. 6 GRBs with Swift XRT and Fermi GBM obs.
ID:
ivo://CDS.VizieR/J/ApJ/880/76
Title:
6 GRBs with Swift XRT and Fermi GBM obs.
Short Name:
J/ApJ/880/76
Date:
21 Oct 2021
Publisher:
CDS
Description:
The jet photosphere has been proposed as the origin for the gamma-ray burst (GRB) prompt emission. In many such models, characteristic features in the spectra appear below the energy range of the Fermi Gamma-ray Burst Monitor (GBM) detectors, so joint fits with X-ray data are important in order to assess the photospheric scenario. Here we consider a particular photospheric model which assumes localized subphotospheric dissipation by internal shocks in a non-magnetized outflow. We investigate it using Bayesian inference and a sample of eight GRBs with known redshifts which are observed simultaneously with Fermi GBM and the Swift X-ray Telescope (XRT). This provides us with an energy range of 0.3keV-40MeV and much tighter parameter constraints. We analyze 32 spectra and find that 16 are well described by the model. We also find that the estimates of the bulk Lorentz factor, {Gamma}, and the fireball luminosity, L_0,52_, decrease while the fraction of dissipated energy, {epsilon}_d_, increases in the joint fits compared to GBM-only fits. These changes are caused by a small excess of counts in the XRT data, relative to the model predictions from fits to GBM-only data. The fact that our limited implementation of the physical scenario yields 50% accepted spectra is promising, and we discuss possible model revisions in the light of the new data. Specifically, we argue that the inclusion of significant magnetization, as well as removing the assumption of internal shocks, will provide better fits at low energies.
184. GRB with early-time optical emission
ID:
ivo://CDS.VizieR/J/ApJ/772/73
Title:
GRB with early-time optical emission
Short Name:
J/ApJ/772/73
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a multi-wavelength analysis of Swift gamma-ray burst GRB 090727, for which optical emission was detected during the prompt {gamma}-ray emission by the 2m autonomous robotic Liverpool Telescope and subsequently monitored for a further two days with the Liverpool and Faulkes Telescopes. Within the context of the standard fireball model, we rule out a reverse shock origin for the early-time optical emission in GRB 090727 and instead conclude that the early-time optical flash likely corresponds to emission from an internal dissipation process. Putting GRB 090727 into a broader observational and theoretical context, we build a sample of 36 {gamma}-ray bursts (GRBs) with contemporaneous early-time optical and {gamma}-ray detections. From these GRBs, we extract a sub-sample of 18 GRBs, which show optical peaks during prompt {gamma}-ray emission, and perform detailed temporal and spectral analysis in {gamma}-ray, X-ray, and optical bands. We find that in most cases early-time optical emission shows sharp and steep behavior, and notice a rich diversity of spectral properties. Using a simple internal shock dissipation model, we show that the emission during prompt GRB phase can occur at very different frequencies via synchrotron radiation. Based on the results obtained from observations and simulation, we conclude that the standard external shock interpretation for early-time optical emission is disfavored in most cases due to sharp peaks ({Delta}t/t<1) and steep rise/decay indices, and that internal dissipation can explain the properties of GRBs with optical peaks during {gamma}-ray emission.
185. GRB X-ray afterglows light curves analysis
ID:
ivo://CDS.VizieR/J/ApJ/826/45
Title:
GRB X-ray afterglows light curves analysis
Short Name:
J/ApJ/826/45
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a correlation between the average temporal decay ({alpha}_X,avg,>200s_) and early-time luminosity (L_X,200s_) of X-ray afterglows of gamma-ray bursts as observed by the Swift X-ray Telescope. Both quantities are measured relative to a rest-frame time of 200s after the {gamma}-ray trigger. The luminosity-average decay correlation does not depend on specific temporal behavior and contains one scale-independent quantity minimizing the role of selection effects. This is a complementary correlation to that discovered by Oates et al. (2012MNRAS.426L..86O, 2015MNRAS.453.4121O) in the optical light curves observed by the Swift Ultraviolet Optical Telescope. The correlation indicates that, on average, more luminous X-ray afterglows decay faster than less luminous ones, indicating some relative mechanism for energy dissipation. The X-ray and optical correlations are entirely consistent once corrections are applied and contamination is removed. We explore the possible biases introduced by different light-curve morphologies and observational selection effects, and how either geometrical effects or intrinsic properties of the central engine and jet could explain the observed correlation.
186. GRB X-ray flare temporal and spectral properties
ID:
ivo://CDS.VizieR/J/ApJ/884/59
Title:
GRB X-ray flare temporal and spectral properties
Short Name:
J/ApJ/884/59
Date:
21 Oct 2021
Publisher:
CDS
Description:
Gamma-ray bursts (GRBs) can be divided into three subclasses: X-ray flash (XRF), X-ray rich (XRR), and classical GRB (C-GRB). An X-ray flare is the rebrightening emission shown in the early X-ray afterglow of some GRBs. In this paper, we comprehensively examine the X-ray flare properties among XRF, XRR, and C-GRB subclasses. We utilize the XRF, XRR, and C-GRB subclass samples obtained from the Swift-BAT3 catalog, and the X-ray flare observational properties are collected from Falcone+ (2007ApJ...671.1921F), Chincarini+ (2010MNRAS.406.2113C), and Yi+ (2016, J/ApJS/224/20). We find that XRFs and XRRs have more bright X-ray flares than C-GRBs. The ratio of the X-ray flare fluence to the prompt emission fluence has different distributions between XRF and C-GRB subclasses. The linear correlation between the duration and the peak time of the X-ray flares is also different between XRF and C-GRB subclasses. We are inclined to identify the GRBs with the bright X-ray flares as XRFs or XRRs. We discuss some issues that are related to the XRF/XRR/C-GRB classification. We also caution the selection effects and the instrument bias in our investigation. Large samples are required in the future to further confirm our results.
187. g'r'i'z'JHKs light curves of GRB 081029
ID:
ivo://CDS.VizieR/J/A+A/531/A39
Title:
g'r'i'z'JHKs light curves of GRB 081029
Short Name:
J/A+A/531/A39
Date:
21 Oct 2021
Publisher:
CDS
Description:
GROND multi-colour follow-up of GRB 081029 is used to study the nature of the late-time extremely fast rebrightening that appears in the optical-NIR light-curve of the afterglow of GRB 081029.
188. g'r'i'z'JH light curves of GRB 091127
ID:
ivo://CDS.VizieR/J/A+A/535/A57
Title:
g'r'i'z'JH light curves of GRB 091127
Short Name:
J/A+A/535/A57
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using high-quality, broad-band afterglow data for GRB 091127, we investigate the validity of the synchrotron fireball model for gamma-ray bursts, and infer physical parameters of the ultra-relativistic outflow. We used multi-wavelength (NIR to X-ray) follow-up observations obtained with GROND simultaneously in the g'r'i'z' JH filters and the XRT onboard the Swift satellite in the 0.3 to 10keV energy range. The resulting afterglow light curve is of excellent accuracy with relative photometric errors as low as 1%, and the spectral energy distribution is well-sampled over 5 decades in energy. These data present one of the most comprehensive observing campaigns for a single GRB afterglow and allow us to test several proposed emission models and outflow characteristics in unprecedented detail.
189. GROND, NOT & VLT/X-shooter obs. of GRB180325A
ID:
ivo://CDS.VizieR/J/ApJ/860/L21
Title:
GROND, NOT & VLT/X-shooter obs. of GRB180325A
Short Name:
J/ApJ/860/L21
Date:
21 Oct 2021
Publisher:
CDS
Description:
The ultraviolet (UV) extinction feature at 2175{AA} is ubiquitously observed in the Galaxy but is rarely detected at high redshifts. Here we report the spectroscopic detection of the 2175{AA} bump on the sightline to the {gamma}-ray burst (GRB) afterglow GRB180325A at z=2.2486, the only unambiguous detection over the past 10 years of GRB follow-up, at four different epochs with the Nordic Optical Telescope (NOT) and the Very Large Telescope (VLT)/X-shooter. Additional photometric observations of the afterglow are obtained with the Gamma-Ray burst Optical and Near-Infrared Detector (GROND). We construct the near-infrared to X-ray spectral energy distributions (SEDs) at four spectroscopic epochs. The SEDs are well described by a single power law and an extinction law with RV~4.4, Av~1.5, and the 2175{AA} extinction feature. The bump strength and extinction curve are shallower than the average Galactic extinction curve. We determine a metallicity of [Zn/H]{>}-0.98 from the VLT/X-shooter spectrum. We detect strong neutral carbon associated with the GRB with equivalent width of Wr({lambda}1656)=0.85+/-0.05. We also detect optical emission lines from the host galaxy. Based on the H{alpha} emission-line flux, the derived dust-corrected star formation rate is ~46+/-4M_{sun}_/yr and the predicted stellar mass is log M*/M_{sun}_~9.3+/-0.4, suggesting that the host galaxy is among the main-sequence star-forming galaxies.
190. Hard X-ray catalog of Sagittarius arm
ID:
ivo://CDS.VizieR/J/PAZh/30/589
Title:
Hard X-ray catalog of Sagittarius arm
Short Name:
J/PAZh/30/589
Date:
21 Oct 2021
Publisher:
CDS
Description:
The images of the Sagittarius arm tangent obtained with the IBIS telescope of the INTEGRAL observatory in the energy range 18-120keV during their observations in the spring of 2003 are analyzed.