scholarly journals On the High‐Energy Spectral Component and Fine Time Structure of Terrestrial Gamma Ray Flashes

2019 ◽  
Vol 124 (14) ◽  
pp. 7484-7497 ◽  
Author(s):  
M. Marisaldi ◽  
M. Galli ◽  
C. Labanti ◽  
N. Østgaard ◽  
D. Sarria ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Spectral Component ◽  
High Energy ◽  
Time Structure ◽  
Fine Time

scholarly journals GAMMA RAY BURSTS AND PARTICLE PHYSICS

1995 ◽  
Vol 10 (38) ◽  
pp. 2897-2913
Author(s):  
DAVID B. CLINE
Keyword(s):  
Black Hole ◽  
Particle Physics ◽  
Gamma Ray ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Primordial Black Hole ◽  
Black Hole Evaporation ◽  
Very High Energy ◽  
Fine Time ◽  
Made In

We provide a brief review of the current situation concerning gamma ray bursts, with emphasis on the role that particle physics may play in the interesting phenomena. The current understanding of GRB origins allows for a large range of physical processes from primordial black hole evaporation to neutron star and black hole collisions. There does not seem to be a simple standard luminosity function and the burst times range from ms to 1000 s of seconds five orders of magnitude. It is likely that some type of fireball model is needed to explain the GRBs. No counterparts of GRB have been detected. We indicate some ways in which progress can be made in either the study of the fine time structure (~μs) or the detection of very high energy photons (>100 GeV to >100 TeV). We also indicate how a small but unique class of the GRB could come from primordial black hole evaporation.

scholarly journals THE VERY BRIGHT AND NEARBY GRB130427A: THE EXTRA HARD SPECTRAL COMPONENT AND IMPLICATIONS FOR VERY HIGH-ENERGY GAMMA-RAY OBSERVATIONS OF GAMMA-RAY BURSTS

2014 ◽  
Vol 28 ◽  
pp. 1460174
Author(s):  
PAK-HIN THOMAS TAM
Keyword(s):  
Gamma Ray ◽  
Spectral Component ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Prompt Gamma ◽  
Large Area ◽  
High Energy Gamma ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

The extended high-energy gamma-ray (>100 MeV) emission occurring after the prompt gamma-ray bursts (GRBs) is usually characterized by a single power-law spectrum, which has been explained as the afterglow synchrotron radiation. We report on the Fermi Large Area Telescope (LAT) observations of the >100 MeV emission from the very bright and nearby GRB 130427A, up to ~100 GeV. By performing time-resolved spectral fits of GRB 130427A, we found a strong evidence of an extra hard spectral component above a few GeV that exists in the extended high-energy emission of this GRB. This extra spectral component may represent the first clear evidence of the long sought-after afterglow inverse Compton emission. Prospects for observations at the very high-energy gamma-rays, i.e., above 100 GeV, are described.

scholarly journals Gamma-ray Bursts at the Highest Energies

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 503
Author(s):  
Lara Nava
Keyword(s):  
Gamma Ray ◽  
Current Knowledge ◽  
Spectral Component ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Special Focus ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
Very High Energy ◽  
Very High

Emission from Gamma-ray bursts is thought to be powered mainly by synchrotron radiation from energetic electrons. The same electrons might scatter these synchrotron seed photons to higher (>10 GeV) energies, building a distinct spectral component (synchrotron self-Compton, SSC). This process is expected to take place, but its relevance (e.g., the ratio between the SSC and synchrotron emitted power) is difficult to predict on the basis of current knowledge of physical conditions at GRB emission sites. Very high-energy radiation in GRBs can be produced also by other mechanisms, such as synchrotron itself (if PeV electrons are produced at the source), inverse Compton on external seed photons, and hadronic processes. Recently, after years of efforts, very high-energy radiation has been finally detected from at least four confirmed long GRBs by the Cherenkov telescopes H.E.S.S. and MAGIC. In all four cases, the emission has been recorded during the afterglow phase, well after the end of the prompt emission. In this work, I give an overview, accessible also to non-experts of the field, of the recent detections, theoretical implications, and future challenges, with a special focus on why very high-energy observations are relevant for our understanding of Gamma-ray bursts and which long-standing questions can be finally answered with the help of these observations.

scholarly journals A new fitting function for GRB MeV spectra based on the internal shock synchrotron model

2020 ◽  
Vol 640 ◽  
pp. A91 ◽  
Author(s):  
M. Yassine ◽  
F. Piron ◽  
F. Daigne ◽  
R. Mochkovitch ◽  
F. Longo ◽  
...  
Keyword(s):  
Physical Model ◽  
Gamma Ray ◽  
Spectral Component ◽  
Emission Spectra ◽  
High Energy ◽  
Spectral Energy ◽  
Parametric Function ◽  
Time Resolved ◽  
Internal Shock ◽  
Prompt Emission

Aims. The physical origin of the gamma-ray burst (GRB) prompt emission is still a subject of debate. Internal shock models have been widely explored, owing to their ability to explain most of the high-energy properties of this emission phase. While the Band function or other phenomenological functions are commonly used to fit GRB prompt emission spectra, we propose a new parametric function that is inspired by an internal shock physical model. We use this function as a proxy of the model to compare it easily to GRB observations. Methods. We built a parametric function that represents the spectral form of the synthetic bursts provided by our internal shock synchrotron model (ISSM). We simulated the response of the Fermi instruments to the synthetic bursts and fit the obtained count spectra to validate the ISSM function. Then, we applied this function to a sample of 74 bright GRBs detected by the Fermi GBM, and we computed the width of their spectral energy distributions around their peak energy. For comparison, we also fit the phenomenological functions that are commonly used in the literature. Finally, we performed a time-resolved analysis of the broadband spectrum of GRB 090926A, which was jointly detected by the Fermi GBM and LAT. This spectrum has a complex shape and exhibits a power-law component with an exponential cutoff at high energy, which is compatible with inverse Compton emission attenuated by gamma-ray internal absorption. Results. This work proposes a new parametric function for spectral fitting that is based on a physical model. The ISSM function reproduces 81% of the spectra in the GBM bright GRB sample, versus 59% for the Band function, for the same number of parameters. It gives also relatively good fits to the GRB 090926A spectra. The width of the MeV spectral component that is obtained from the fits of the ISSM function is slightly larger than the width from the Band fits, but it is smaller when observed over a wider energy range. Moreover, all of the 74 analyzed spectra are found to be significantly wider than the synthetic synchrotron spectra. We discuss possible solutions to reconcile the observations with the internal shock synchrotron model, such as an improved modeling of the shock microphysics or more accurate spectral measurements at MeV energies.

scholarly journals GRB 210121A: A Typical Fireball Burst Detected by Two Small Missions

2021 ◽  
Vol 922 (2) ◽  
pp. 237
Author(s):  
Xiangyu Ivy Wang ◽  
Xutao Zheng ◽  
Shuo Xiao ◽  
Jun Yang ◽  
Zi-Ke Liu ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Spectral Component ◽  
High Energy ◽  
Physical Models ◽  
Host Galaxy ◽  
Initial Radius ◽  
Peak Energy ◽  
Energy Indices ◽  
Sky Monitor ◽  
Integrated Detectors

Abstract The Chinese CubeSat Mission, Gamma Ray Integrated Detectors (GRID), recently detected its first gamma-ray burst, GRB 210121A, which was jointly observed by the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM). This burst is confirmed by several other missions, including Fermi and Insight-HXMT. We combined multimission observational data and performed a comprehensive analysis of the burst’s temporal and spectral properties. Our results show that the burst is relatively special in its high peak energy, thermal-like low-energy indices, and large fluence. By putting it to the E p –E γ,iso relation diagram with assumed distance, we found that this burst can be constrained at the redshift range of [0.3, 3.0]. The thermal spectral component is also confirmed by the direct fit of the physical models to the observed spectra. Interestingly, the physical photosphere model also constrained a redshift of z ∼ 0.3 for this burst, which helps us to identify a host galaxy candidate at such a distance within the location error box. Assuming that the host galaxy is real, we found that the burst can be best explained by the photosphere emission of a typical fireball with an initial radius of r 0 ∼ 3.2 × 107 cm.

FEATURES OF MAGNETIC STRUCTURE OF SUNSPOTS GROUPS AT DEVELOPMENT OF SUSTAINED FLUXES HIGH ENERGY GAMMA RAY

2020 ◽  
Vol 3 (331) ◽  
pp. 66-72
Author(s):  
Gennady Sergeevich, Minasyants ◽  
◽  
Tamara Mihailovna, Minasyants ◽  
Vladimir Mihailovich, Tomozov ◽  
◽  
...  
Keyword(s):  
Magnetic Structure ◽  
Gamma Ray ◽  
High Energy ◽  
High Energy Gamma ◽  
Energy Gamma

scholarly journals UVscope and its application aboard the ASTRI-Horn telescope

2021 ◽  
Author(s):  
Maria Concetta Maccarone ◽  
Giovanni La Rosa ◽  
Osvaldo Catalano ◽  
Salvo Giarrusso ◽  
Alberto Segreto ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Single Photon ◽  
Photon Counting ◽  
Light Flux ◽  
Cosmic Ray ◽  
High Energy ◽  
Wide Field ◽  
High Energy Astrophysics ◽  
Single Photon Counting ◽  
Photon Counting Mode

AbstractUVscope is an instrument, based on a multi-pixel photon detector, developed to support experimental activities for high-energy astrophysics and cosmic ray research. The instrument, working in single photon counting mode, is designed to directly measure light flux in the wavelengths range 300-650 nm. The instrument can be used in a wide field of applications where the knowledge of the nocturnal environmental luminosity is required. Currently, one UVscope instrument is allocated onto the external structure of the ASTRI-Horn Cherenkov telescope devoted to the gamma-ray astronomy at very high energies. Being co-aligned with the ASTRI-Horn camera axis, UVscope can measure the diffuse emission of the night sky background simultaneously with the ASTRI-Horn camera, without any interference with the main telescope data taking procedures. UVscope is properly calibrated and it is used as an independent reference instrument for test and diagnostic of the novel ASTRI-Horn telescope.

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