scholarly journals Gamma Ray Bursts in the Fermi era: the spectral energy distribution of the prompt emission

2010 ◽  
Author(s):  
F. Massaro ◽  
J. E. Grindlay ◽  
A. Paggi ◽  
Nobuyuki Kawai ◽  
Shigehiro Nagataki
Keyword(s):  
Energy Distribution ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Gamma Ray Bursts ◽  
Spectral Energy ◽  
Prompt Emission

scholarly journals Prevalence of Extra Power-Law Spectral Components in Short Gamma-Ray Bursts

2021 ◽  
Vol 922 (2) ◽  
pp. 255
Author(s):  
Qing-Wen Tang ◽  
Kai Wang ◽  
Liang Li ◽  
Ruo-Yu Liu
Keyword(s):  
Power Law ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Spectral Feature ◽  
Gamma Ray Bursts ◽  
Spectral Energy ◽  
Spectral Components ◽  
Short Grbs ◽  
Prompt Emission ◽  
Emission Phase

Abstract A prompt extra power-law (PL) spectral component that usually dominates the spectral energy distribution below tens of keV or above ∼10 MeV has been discovered in some bright gamma-ray bursts (GRBs). However, its origin is still unclear. In this paper, we present a systematic analysis of 13 Fermi short GRBs, as of 2020 August, with contemporaneous keV–MeV and GeV detections during the prompt emission phase. We find that the extra PL component is a ubiquitous spectral feature for short GRBs, showing up in all 13 analyzed GRBs. The PL indices are mostly harder than −2.0, which may be well reproduced by considering the electromagnetic cascade induced by ultrarelativistic protons or electrons accelerated in the prompt emission phase. The average flux of these extra PL components positively correlates with that of the main spectral components, which implies they may share the same physical origin.

scholarly journals Limits on quantum gravity effects from Swift short gamma-ray bursts

2017 ◽  
Vol 607 ◽  
pp. A121 ◽  
Author(s):  
M. G. Bernardini ◽  
G. Ghirlanda ◽  
S. Campana ◽  
P. D’Avanzo ◽  
J.-L. Atteia ◽  
...  
Keyword(s):  
Quantum Gravity ◽  
Gamma Ray ◽  
Lorentz Invariance ◽  
Spectral Energy Distribution ◽  
Gamma Ray Bursts ◽  
Low Energy ◽  
Energy Separation ◽  
Spectral Energy ◽  
Spectral Evolution ◽  
Short Grbs

The delay in arrival times between high and low energy photons from cosmic sources can be used to test the violation of the Lorentz invariance (LIV), predicted by some quantum gravity theories, and to constrain its characteristic energy scale EQG that is of the order of the Planck energy. Gamma-ray bursts (GRBs) and blazars are ideal for this purpose thanks to their broad spectral energy distribution and cosmological distances: at first order approximation, the constraints on EQG are proportional to the photon energy separation and the distance of the source. However, the LIV tiny contribution to the total time delay can be dominated by intrinsic delays related to the physics of the sources: long GRBs typically show a delay between high and low energy photons related to their spectral evolution (spectral lag). Short GRBs have null intrinsic spectral lags and are therefore an ideal tool to measure any LIV effect. We considered a sample of 15 short GRBs with known redshift observed by Swift and we estimate a limit on EQG ≳ 1.5 × 1016 GeV. Our estimate represents an improvement with respect to the limit obtained with a larger (double) sample of long GRBs and is more robust than the estimates on single events because it accounts for the intrinsic delay in a statistical sense.

scholarly journals A search for radio afterglows from gamma-ray bursts with the Australian Square Kilometre Array Pathfinder

2021 ◽  
Vol 503 (2) ◽  
pp. 1847-1863
Author(s):  
James K Leung ◽  
Tara Murphy ◽  
Giancarlo Ghirlanda ◽  
David L Kaplan ◽  
Emil Lenc ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Phase 1 ◽  
Spectral Energy Distribution ◽  
Early Time ◽  
Gamma Ray Bursts ◽  
Spectral Energy ◽  
Density Parameter ◽  
Square Kilometre Array ◽  
Optical Images ◽  
Celestial Sphere

ABSTRACT We present a search for radio afterglows from long gamma-ray bursts using the Australian Square Kilometre Array Pathfinder (ASKAP). Our search used the Rapid ASKAP Continuum Survey, covering the entire celestial sphere south of declination +41○, and three epochs of the Variables and Slow Transients Pilot Survey (Phase 1), covering ∼5000 square degrees per epoch. The observations we used from these surveys spanned a nine-month period from 2019 April 21 to 2020 January 11. We cross-matched radio sources found in these surveys with 779 well-localized (to ≤15 arcsec) long gamma-ray bursts occurring after 2004 and determined whether the associations were more likely afterglow- or host-related through the analysis of optical images. In our search, we detected one radio afterglow candidate associated with GRB 171205A, a local low-luminosity gamma-ray burst with a supernova counterpart SN 2017iuk, in an ASKAP observation 511 d post-burst. We confirmed this detection with further observations of the radio afterglow using the Australia Telescope Compact Array at 859 and 884 d post-burst. Combining this data with archival data from early-time radio observations, we showed the evolution of the radio spectral energy distribution alone could reveal clear signatures of a wind-like circumburst medium for the burst. Finally, we derived semi-analytical estimates for the microphysical shock parameters of the burst: electron power-law index p = 2.84, normalized wind-density parameter A* = 3, fractional energy in electrons ϵe = 0.3, and fractional energy in magnetic fields ϵB = 0.0002.

scholarly journals Spectral and morphological study of the gamma radiation of the middle-aged supernova remnant HB 21

2019 ◽  
Vol 623 ◽  
pp. A86 ◽  
Author(s):  
L. Ambrogi ◽  
R. Zanin ◽  
S. Casanova ◽  
E. De Oña Wilhelmi ◽  
G. Peron ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Electron Spectrum ◽  
Supernova Remnant ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Three Dimensional ◽  
Spectral Energy ◽  
Proton Spectrum ◽  
Middle Aged ◽  
Gamma Ray Emission

Aims. We investigate the nature of the accelerated particles responsible for the production of the gamma-ray emission observed from the middle-aged supernova remnant (SNR) HB 21. Methods. We present the analysis of more than nine years of Fermi LAT data from the SNR HB 21. We performed morphological and spectral analysis of the SNR by means of a three-dimensional binned likelihood analysis. To assess the intrinsic properties of the parent particle models, we fit the obtained gamma-ray spectral energy distribution of the SNR by both hadronic- and leptonic-induced gamma-ray spectrum. Results. We observe an extended emission positionally in agreement with the SNR HB 21. The bulk of this gamma-ray emission is detected from the remnant; photons up to ~10 GeV show clear evidence of curvature at the lower energies. The remnant is characterized by an extension of 0°.83, that is, 30% smaller than claimed in previous studies. The increased statistics allowed us also to resolve a point-like source at the edge of the remnant, in proximity to a molecular cloud of the Cyg OB7 complex. In the southern part of the remnant, a hint of an additional gamma-ray excess in correspondence to shocked molecular clouds is observed. Conclusions. The spectral energy distribution of the SNR shows evidence of a break around 400 MeV, which can be properly fitted within both the hadronic and leptonic scenario. The pion-decay mechanism reproduces well the gamma rays, postulating a proton spectrum with a slope ~2.5 and with a steepening around tens of GeV, which could be explained by the energy-dependent escape of particles from the remnant. In the leptonic scenario the electron spectrum within the SNR matches closely the locally measured spectrum. This remarkable and novel result shows that SNR HB 21 could be a direct contributor to the population of Galactic electrons. In the leptonic scenario, we find that the local electron spectrum with a break around 2 GeV, closely evokes the best-fitting parental spectrum within this SNR. If such a scenario is confirmed, this would indicate that the SNR might be a source of Galactic background electrons.

scholarly journals A complete sample of long bright Swift gamma ray bursts

2013 ◽  
Vol 371 (1992) ◽  
pp. 20120235 ◽  
Author(s):  
Gianpiero Tagliaferri ◽  
Ruben Salvaterra ◽  
Sergio Campana ◽  
Stefano Covino ◽  
Paolo D’Avanzo ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Gamma Ray ◽  
Cosmic Time ◽  
Gamma Ray Bursts ◽  
Spectral Energy ◽  
Complete Sample ◽  
Peak Flux ◽  
S Peak ◽  
Prompt Emission

Complete samples are the basis of any population study. To this end, we selected a complete subsample of Swift long bright gamma ray bursts (GRBs). The sample, made up of 58 bursts, was selected by considering bursts with favourable observing conditions for ground-based follow-up observations and with the 15–150 keV 1 s peak flux above a flux threshold of 2.6 photons cm −2  s −1 . This sample has a redshift completeness level higher than 90 per cent. Using this complete sample, we investigate the properties of long GRBs and their evolution with cosmic time, focusing in particular on the GRB luminosity function, the prompt emission spectral-energy correlations and the nature of dark bursts.

Gamma-ray bursts spectral correlations and their cosmological use

2007 ◽  
Vol 365 (1854) ◽  
pp. 1385-1394 ◽  
Author(s):  
Giancarlo Ghirlanda
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Spectral Energy ◽  
Selection Effects ◽  
Emission Energy ◽  
X Ray ◽  
New Class ◽  
The Universe ◽  
Prompt Emission ◽  
Open Issues

The correlations involving the long-gamma-ray bursts (GRBs) prompt emission energy represent a new key to understand the GRB physics. These correlations have been proved to be the tool that makes long-GRBs a new class of standard candles. Gamma Ray Bursts, being very powerful cosmological sources detected in the hard X-ray band, represent a new tool to investigate the Universe in a redshift range, which is complementary to that covered by other cosmological probes (SNIa and CMB). A review of the , , and correlations is presented. Open issues related to these correlations (e.g. presence of outliers and selection effects) and to their use for cosmographic purposes (e.g. dependence on model assumptions) are discussed. Finally, the relevance of thermal components in GRB spectra is discussed in the light of some of the models recently proposed for the interpretation of the spectral-energy correlations.

The origin of HE and VHE gamma-ray flares from FSRQs

2018 ◽  
Vol 27 (10) ◽  
pp. 1844007
Author(s):  
S. Gasparyan ◽  
N. Sahakyan ◽  
P. Chardonnet
Keyword(s):  
Energy Distribution ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Cherenkov Telescopes ◽  
Spectrum Radio ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

The discovery of very-high-energy gamma-ray emission from Flat Spectrum Radio Quasars (FSRQs) by ground-based Cherenkov telescopes (HESS, MAGIC, VERITAS) provides a new view of blazar emission processes. The available data from multiwavelength observations of FSRQs, allow us to constrain the size (possibly also location) of the emitting region, magnetic field, electron energy distribution, etc., which are crucial for the understanding of the jet properties. We investigate the origin of emission from FSRQs (PKS 1510-089, PKS 1222+216 and 3C 279) by modeling the broadband spectral energy distribution in their quiescent and flaring states, using estimation of the parameter space that describes the underlying particle distribution responsible for the emission through the Markov Chain Monte Carlo (MCMC) technique.

scholarly journals On the Origin of Gamma-Ray Flares from Bright Fermi Blazars

2021 ◽  
Vol 257 (2) ◽  
pp. 37
Author(s):  
Vaidehi S. Paliya ◽  
M. Böttcher ◽  
Mark Gurwell ◽  
C. S. Stalin
Keyword(s):  
Energy Distribution ◽  
Magnetic Reconnection ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Pivotal Role ◽  
Jet Physics ◽  
Spectral Energy ◽  
Electron Population ◽  
Doppler Factor

Abstract The origin of γ-ray flares observed from blazars is one of the major mysteries in jet physics. We have attempted to address this problem following a novel spectral energy distribution (SED) fitting technique that explored the flaring patterns identified in the broadband SEDs of two γ-ray bright blazars, 3C 279 (z = 0.54) and 3C 454.3 (z = 0.86), using near-simultaneous radio-to-γ-ray observations. For both sources, the γ-ray flux strongly correlates with the separation of the SED peaks and the Compton dominance. We propose that spectral hardening of the radiating electron population and/or enhancement of the Doppler factor can naturally explain these observations. In both cases, magnetic reconnection may play a pivotal role in powering the luminous γ-ray flares.

scholarly journals The spectral energy distribution of an X-ray pair halo from a gamma-ray source with a power-law continuum

2021 ◽  
Vol 2145 (1) ◽  
pp. 012013
Author(s):  
A Eungwanichayapant ◽  
W Luangtip
Keyword(s):  
Energy Distribution ◽  
Power Law ◽  
Gamma Ray ◽  
Energy Levels ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Maximum Energy ◽  
Spectral Energy ◽  
Power Indices ◽  
X Ray

Abstract Interactions between Very High Energy (VHE) gamma-rays from Active Galactic Nuclei (AGNs) and infrared photons from the Extragalactic Background Light (EBL) can start electromagnetic cascades. If the extragalactic magnetic field near a host galaxy is strong enough (∼1 µG), the cascades would develop isotropically around the AGN. As a result, the electron/positron pairs created along the development of the cascades would create an X-ray halo via synchrotron radiation process. It is believed that the VHE gamma-ray spectra from the AGNs could be approximated by a power-law model which is truncated at high energy end (i.e. maximum energy). In this work we studied the X-ray Spectral Energy Distribution (SED) of the halo generated from the AGN spectra with different power indices and maximum energy levels. The results showed that the SEDs were slightly higher and broader, as they were obtaining higher flux if the power indices were lower. On the other hand, the SEDs were sensitive to the maximum energy levels between 100-300 TeV. More flux could be obtained from the higher maximum energy. However, we found that the SED becomes insensitive to the varied parameters when the maximum energy and the power index are > 500 TeV and < 1.5, respectively.

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