scholarly journals The POLAR gamma-ray burst polarization catalog

2020 ◽  
Vol 644 ◽  
pp. A124 ◽  
Author(s):  
M. Kole ◽  
N. De Angelis ◽  
F. Berlato ◽  
J. M. Burgess ◽  
N. Gauvin ◽  
...  
Keyword(s):  
Linear Polarization ◽  
Gamma Ray ◽  
Integrated Analysis ◽  
Polarization Angle ◽  
Analysis Tool ◽  
Time Resolved ◽  
Gamma Ray Burst ◽  
Polarization Measurements ◽  
Open Questions ◽  
Polarization Studies

Context. Despite over 50 years of research, many open questions remain about the origin and nature of gamma-ray bursts (GRBs). Linear polarization measurements of the prompt emission of these extreme phenomena have long been thought to be key to answering a range of these questions. The POLAR detector was designed to produce the first set of detailed and reliable linear polarization measurements in the 50 − 500 keV energy range. During late 2016 and early 2017, POLAR detected a total of 55 GRBs. The analysis results of 5 of these GRBs have been reported, and were found to be consistent with a low or unpolarized flux. However, previous reports by other collaborations found high levels of linear polarization, including some as high as 90%. Aims. We study the linear polarization for the 14 GRBs observed by POLAR for which statistically robust inferences are possible. Additionally, time-resolved polarization studies are performed on GRBs with sufficient apparent flux. Methods. A publicly available polarization analysis tool, developed within the Multi-Mission Maximum Likelihood framework (3ML), was used to produce statistically robust results. The method allows spectral and polarimetric data from POLAR to be combined with spectral data from the Fermi Gamma-ray Burst Monitor (Fermi-GBM) and the Neil Gehrels Swift Observatory to jointly model the spectral and polarimetric parameters. Results. The time-integrated analysis finds all results to be compatible with low or zero polarization with the caveat that, when time-resolved analysis is possible within individual pulses, we observe moderate linear polarization with a rapidly changing polarization angle. Therefore, time-integrated polarization results, while pointing to lower polarization, are potentially an artifact of summing over the changing polarization signal and thus washing out the true moderate polarization. We therefore caution against overinterpretation of any time-integrated results inferred herein and encourage the community to wait for more detailed polarization measurements from forthcoming missions such as POLAR-2 and LEAP.

scholarly journals First Detection of Radio Linear Polarization in a Gamma-Ray Burst Afterglow

2019 ◽  
Vol 884 (2) ◽  
pp. L58 ◽  
Author(s):  
Yuji Urata ◽  
Kenji Toma ◽  
Kuiyun Huang ◽  
Keiichi Asada ◽  
Hiroshi Nagai ◽  
...  
Keyword(s):  
Linear Polarization ◽  
Gamma Ray ◽  
Gamma Ray Burst

scholarly journals Time-resolved GRB polarization with POLAR and GBM

2019 ◽  
Vol 627 ◽  
pp. A105 ◽  
Author(s):  
J. M. Burgess ◽  
M. Kole ◽  
F. Berlato ◽  
J. Greiner ◽  
G. Vianello ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Single Pulse ◽  
Current Data ◽  
Gamma Ray Bursts ◽  
Polarization Angle ◽  
Analysis Pipeline ◽  
Time Resolved ◽  
Polarization Models ◽  
Probabilistic Context ◽  
Prompt Emission

Context. Simultaneousγ-ray measurements ofγ-ray burst spectra and polarization offer a unique way to determine the underlying emission mechanism(s) in these objects, as well as probing the particle acceleration mechanism(s) that lead to the observedγ-ray emission.Aims. We examine the jointly observed data from POLAR andFermi-GBM of GRB 170114A to determine its spectral and polarization properties, and seek to understand the emission processes that generate these observations. We aim to develop an extensible and statistically sound framework for these types of measurements applicable to other instruments.Methods. We leveraged the existing3MLanalysis framework to develop a new analysis pipeline for simultaneously modeling the spectral and polarization data. We derived the proper Poisson likelihood forγ-ray polarization measurements in the presence of background. The developed framework is publicly available for similar measurements with otherγ-ray polarimeters. The data are analyzed within a Bayesian probabilistic context and the spectral data from both instruments are simultaneously modeled with a physical, numerical synchrotron code.Results. The spectral modeling of the data is consistent with a synchrotron photon model as has been found in a majority of similarly analyzed single-pulse gamma-ray bursts. The polarization results reveal a slight trend of growing polarization in time reaching values of ∼30% at the temporal peak of the emission. We also observed that the polarization angle evolves with time throughout the emission. These results suggest a synchrotron origin of the emission but further observations of many GRBs are required to verify these evolutionary trends. Furthermore, we encourage the development of time-resolved polarization models for the prompt emission of gamma-ray bursts as the current models are not predictive enough to enable a full modeling of our current data.

Gamma-ray linear polarization measurements inBa129

1978 ◽  
Vol 17 (2) ◽  
pp. 596-600 ◽  
Author(s):  
J. Gizon ◽  
A. Gizon ◽  
Y. K. Lee ◽  
D. O. Elliott
Keyword(s):  
Linear Polarization ◽  
Gamma Ray ◽  
Polarization Measurements

scholarly journals A Bayesian Fermi-GBM short GRB spectral catalogue

2019 ◽  
Vol 490 (1) ◽  
pp. 927-946 ◽  
Author(s):  
J Michael Burgess ◽  
Jochen Greiner ◽  
Damien Bégué ◽  
Franceso Berlato
Keyword(s):  
Light Curve ◽  
Gravitational Wave ◽  
Power Law ◽  
Gamma Ray ◽  
Posterior Distributions ◽  
Time Resolved ◽  
Gamma Ray Burst ◽  
Posterior Predictive Checks ◽  
Peak Flux ◽  
Reduced Data

ABSTRACT Inspired by the confirmed detection of a short gamma-ray burst (GRB) in association with a gravitational wave signal, we present the first Bayesian Fermi-Gamma-ray Burst Monitor (GBM) short GRB spectral catalogue. Both peak flux and time-resolved spectral results are presented. Data are analysed with the proper Poisson likelihood allowing us to provide statistically reliable results even for spectra with few counts. All fits are validated with posterior predictive checks. We find that nearly all spectra can be modelled with a cut-off power law. Additionally, we release the full posterior distributions and reduced data from our sample. Following our previous study, we introduce three variability classes based on the observed light-curve structure.

scholarly journals TheFermiGBM gamma-ray burst time-resolved spectral catalog: brightest bursts in the first four years

2016 ◽  
Vol 588 ◽  
pp. A135 ◽  
Author(s):  
Hoi-Fung Yu ◽  
Robert D. Preece ◽  
Jochen Greiner ◽  
P. Narayana Bhat ◽  
Elisabetta Bissaldi ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Time Resolved ◽  
Gamma Ray Burst ◽  
Burst Time

scholarly journals Constraints on Lorentz Invariance Violation from Optical Polarimetry of Astrophysical Objects

Symmetry ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 596 ◽  
Author(s):  
Fabian Kislat
Keyword(s):  
Standard Model ◽  
Quantum Gravity ◽  
Linear Polarization ◽  
Lorentz Invariance ◽  
Polarization Angle ◽  
Standard Model Extension ◽  
Polarization Measurements ◽  
Invariance Violation ◽  
The Standard Model ◽  
Lorentz Invariance Violation

Theories of quantum gravity suggest that Lorentz invariance, the fundamental symmetry of the Theory of Relativity, may be broken at the Planck energy scale. While any deviation from conventional Physics must be minuscule in particular at attainable energies, this hypothesis motivates ever more sensitive tests of Lorentz symmetry. In the photon sector, astrophysical observations, in particular polarization measurements, are a very powerful tool because tiny deviations from Lorentz invariance will accumulate as photons propagate over cosmological distances. The Standard-Model Extension (SME) provides a theoretical framework in the form of an effective field theory that describes low-energy effects due to a more fundamental quantum gravity theory by adding additional terms to the Standard Model Lagrangian. These terms can be ordered by the mass dimension d of the corresponding operator and lead to a wavelength, polarization, and direction dependent phase velocity of light. Lorentz invariance violation leads to an energy-dependent change of the Stokes vector as photons propagate, which manifests itself as a rotation of the polarization angle in measurements of linear polarization. In this paper, we analyze optical polarization measurements from 63 Active Galactic Nuclei (AGN) and Gamma-ray Bursts (GRBs) to search for Lorentz violating signals. We use both spectropolarimetric measurements, which directly constrain the change of linear polarization angle, as well as broadband spectrally integrated measurements. In the latter, Lorentz invariance violation manifests itself by reducing the observed net polarization fraction. Any observation of non-vanishing linear polarization thus leads to constraints on the magnitude of Lorentz violating effects. We derive the first set limits on each of the 10 individual birefringent coefficients of the minimal SME with d = 4 , with 95% confidence limits on the order of 10−34 on the dimensionless coefficients.

Gamma ray linear polarization measurements forAl29

1975 ◽  
Vol 11 (4) ◽  
pp. 1111-1116 ◽  
Author(s):  
J. R. Williams ◽  
R. O. Nelson ◽  
C. R. Gould ◽  
D. R. Tilley
Keyword(s):  
Linear Polarization ◽  
Gamma Ray ◽  
Polarization Measurements

scholarly journals GAMMA-RAY BURST PROMPT EMISSION

2014 ◽  
Vol 23 (02) ◽  
pp. 1430002 ◽  
Author(s):  
BING ZHANG
Keyword(s):  
Gamma Ray ◽  
Spectral Component ◽  
Broad Band ◽  
Current Data ◽  
Radiation Mechanism ◽  
Main Band ◽  
Gamma Ray Burst ◽  
Open Questions ◽  
Dominant Band ◽  
Prompt Emission

The origin of gamma-ray burst (GRB) prompt emission, bursts of γ-rays lasting from shorter than one second to thousands of seconds, remains not fully understood after more than 40 years of observations. The uncertainties lie in several open questions in the GRB physics, including jet composition, energy dissipation mechanism, particle acceleration mechanism and radiation mechanism. Recent broad-band observations of prompt emission with Fermi sharpen the debates in these areas, which stimulated intense theoretical investigations invoking very different ideas. I will review these debates, and argue that the current data suggest the following picture: A quasi-thermal spectral component originating from the photosphere of the relativistic ejecta has been detected in some GRBs. Even though in some cases (e.g. GRB 090902B) this component dominates the spectrum, in most GRBs, this component either forms a sub-dominant "shoulder" spectral component in the low energy spectral regime of the more dominant "Band" component, or is not detectable at all. The main "Band" spectral component likely originates from the optically thin region due to synchrotron radiation. The diverse magnetization in the GRB central engine is likely the origin of the observed diverse prompt emission properties among bursts.

scholarly journals Interpreting the Behavior of Time‐resolved Gamma‐Ray Burst Spectra

2002 ◽  
Vol 565 (1) ◽  
pp. 182-194 ◽  
Author(s):  
Nicole M. Lloyd‐Ronning ◽  
Vahe Petrosian
Keyword(s):  
Gamma Ray ◽  
Time Resolved ◽  
Gamma Ray Burst
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