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 Very High Energy gamma-rays from blazars

2013 ◽  
Vol 9 (S304) ◽  
pp. 119-124
Author(s):  
Helene Sol
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Low Frequency ◽  
High Energy ◽  
Spectral Energy ◽  
Bl Lac Objects ◽  
Cherenkov Telescopes ◽  
Bl Lac ◽  
Very High Energy ◽  
Very High

AbstractThe extragalactic very high energy (VHE) gamma-ray sky is dominated at the moment by more than fifty blazars detected by the present imaging atmospheric Cherenkov telescopes (IACT), with a majority (about 90%) of high-frequency peaked BL Lac objects (HBL) and a small number of low-frequency peaked and intermediate BL Lac objects (LBL and IBL) and flat spectrum radio quasars (FSRQ). A significant variability is often observed, with time scales from a few minutes to months and years. The spectral energy distribution (SED) of these blazars typically shows two bumps from the radio to the TeV range, which can usually be described by leptonic or hadronic processes. While elementary bricks of the VHE emission scenarios seem now reasonably well identified, a global picture of these sources, describing the geometry and dynamics of the VHE zone, is not yet available. Multiwavelength monitoring and global alert network will be important to better constrain the picture, especially with the perspective of CTA, a major project of the next generation in ground-based gamma-ray astronomy.

scholarly journals Very high energy gamma-rays from flat spectrum radio quasars

2014 ◽  
Vol 10 (S313) ◽  
pp. 27-32
Author(s):  
Elina Lindfors
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
High Energy ◽  
High Energy Gamma ◽  
Spectrum Radio ◽  
Very High Energy ◽  
Energy Gamma ◽  
Emission Models ◽  
Γ Rays ◽  
Very High

AbstractThe detection of Flat Spectrum Radio Quasars (FSRQs) in the Very High Energy (VHE, E>100 GeV) range is challenging, mainly because of their steep soft spectra and distance. Nevertheless four FSRQs are now known to be VHE emitters. The detection of the VHE γ-rays has challenged the emission models of these sources. The sources are also found to exhibit very different behavior. I will give an overview of what is known about the VHE emission of these sources and about the multiwavelength signatures that are connected to the VHE gamma-ray emission.

scholarly journals A fast muon tagger method for Imaging Atmospheric Cherenkov Telescopes

2020 ◽  
Vol 1548 (1) ◽  
pp. 012036
Author(s):  
L Di Venere ◽  
G Giavitto ◽  
F Giordano ◽  
R López-Coto ◽  
R Pillera
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Silicon Photomultiplier ◽  
Cherenkov Telescopes ◽  
Large Size ◽  
Very High Energy ◽  
Energy Gamma ◽  
Design Options ◽  
Very High ◽  
Computation Speed

Abstract The Cherenkov Telescope Array (CTA) will be the next major observatory for Very High Energy gamma-ray astronomy. Its optical throughput calibration relies on muon Cherenkov rings. This work is aimed at developing a fast and efficient muon tagger at the camera level for the CTA telescopes. A novel technique to tag muons using the capabilities of silicon photomultiplier Compact High-Energy Camera CHEC-S, one of the design options for the camera of the small size telescopes, has been developed, studying and comparing different algorithms such as circle fitting with the Taubin method, machine learning using a neural network and simple pixel counting. Their performance in terms of efficiency and computation speed was investigated using simulations with varying levels of night sky background light. The application of the best performing method to the large size telescope camera has also been studied, to improve the speed of the muon preselection.

scholarly journals Observation of the Gamma-Ray Binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS Telescopes

2021 ◽  
Vol 923 (2) ◽  
pp. 241
Author(s):  
C. B. Adams ◽  
W. Benbow ◽  
A. Brill ◽  
J. H. Buckley ◽  
M. Capasso ◽  
...  
Keyword(s):  
Binary Systems ◽  
Gamma Ray ◽  
High Energy ◽  
Energy Bands ◽  
X Ray ◽  
Cherenkov Telescopes ◽  
Orbital Cycles ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

Abstract The results of gamma-ray observations of the binary system HESS J0632 + 057 collected during 450 hr over 15 yr, between 2004 and 2019, are presented. Data taken with the atmospheric Cherenkov telescopes H.E.S.S., MAGIC, and VERITAS at energies above 350 GeV were used together with observations at X-ray energies obtained with Swift-XRT, Chandra, XMM-Newton, NuSTAR, and Suzaku. Some of these observations were accompanied by measurements of the Hα emission line. A significant detection of the modulation of the very high-energy gamma-ray fluxes with a period of 316.7 ± 4.4 days is reported, consistent with the period of 317.3 ± 0.7 days obtained with a refined analysis of X-ray data. The analysis of data from four orbital cycles with dense observational coverage reveals short-timescale variability, with flux-decay timescales of less than 20 days at very high energies. Flux variations observed over a timescale of several years indicate orbit-to-orbit variability. The analysis confirms the previously reported correlation of X-ray and gamma-ray emission from the system at very high significance, but cannot find any correlation of optical Hα parameters with fluxes at X-ray or gamma-ray energies in simultaneous observations. The key finding is that the emission of HESS J0632 + 057 in the X-ray and gamma-ray energy bands is highly variable on different timescales. The ratio of gamma-ray to X-ray flux shows the equality or even dominance of the gamma-ray energy range. This wealth of new data is interpreted taking into account the insufficient knowledge of the ephemeris of the system, and discussed in the context of results reported on other gamma-ray binary systems.

scholarly journals Measurement of the EBL spectral energy distribution using the VHE γ-ray spectra of H.E.S.S. blazars

2017 ◽  
Vol 606 ◽  
pp. A59 ◽  
Author(s):  
◽  
H. Abdalla ◽  
A. Abramowski ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Extragalactic Background Light ◽  
Cherenkov Telescopes ◽  
Spectral Bands ◽  
Electron Positron ◽  
Very High Energy ◽  
Model Independent

Very high-energy γ rays (VHE, E ≳ 100 GeV) propagating over cosmological distances can interact with the low-energy photons of the extragalactic background light (EBL) and produce electron-positron pairs. The transparency of the Universe to VHE γ rays is then directly related to the spectral energy distribution (SED) of the EBL. The observation of features in the VHE energy spectra of extragalactic sources allows the EBL to be measured, which otherwise is very difficult. An EBL model-independent measurement of the EBL SED with the H.E.S.S. array of Cherenkov telescopes is presented. It was obtained by extracting the EBL absorption signal from the reanalysis of high-quality spectra of blazars. From H.E.S.S. data alone the EBL signature is detected at a significance of 9.5σ, and the intensity of the EBL obtained in different spectral bands is presented together with the associated γ-ray horizon.

scholarly journals Empirical multi-wavelength prediction method for Very High Energy Gamma-ray emitting BL Lacs

2016 ◽  
Vol 12 (S324) ◽  
pp. 239-240
Author(s):  
V. Fallah Ramazani ◽  
E. Lindfors ◽  
K. Nilsson
Keyword(s):  
Gamma Ray ◽  
Prediction Method ◽  
High Energy ◽  
Linear Regression Method ◽  
Cherenkov Telescopes ◽  
Multi Wavelength ◽  
Very High Energy ◽  
Energy Gamma ◽  
Bl Lacs ◽  
Very High

AbstractWe present the most up-to-date and complete multi-wavelength correlation analysis on luminosity properties of TeV BL Lacs. Correlation function (power law or linear) parameters are calculated based on linear regression method. Using the lower energy luminosities of a sample of 182 non-TeV BL Lacs and the generated functions, minimum level of VHE gamma-ray emission was calculated for each non-TeV BL Lacs. This multi wavelength prediction method gives us a list of best candidates to be observed with current generation of Imaging Air Cherenkov Telescopes.

scholarly journals Te-REX: a sample of extragalactic TeV-emitting candidates

2019 ◽  
Vol 492 (3) ◽  
pp. 3728-3741
Author(s):  
Barbara Balmaverde ◽  
A Caccianiga ◽  
R Della Ceca ◽  
A Wolter ◽  
A Belfiore ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Host Galaxy ◽  
Spectral Energy ◽  
X Rays ◽  
X Ray ◽  
Cherenkov Telescopes ◽  
Sky Survey ◽  
Very High Energy ◽  
Energy Gamma

ABSTRACT The REX (Radio-Emitting X-ray sources) is a catalogue produced by cross-matching X-ray data from the ROSAT-PSPC archive of pointed observations and radio data from the NRAO VLA Sky Survey, aimed at the selection of blazars. From the REX catalogue, we select a well-defined and statistically complete sample of high-energy peaked BL Lac (HBL). HBL are expected to be the most numerous class of extragalactic TeV-emitting sources. Specifically, we have considered only the REX sources in the currently planned CTA extragalactic survey area satisfying specific criteria and with an optical spectroscopic confirmation. We obtain 46 HBL candidates that we called Te-REX (TeV-emitting REX). We estimate the very high-energy gamma-ray emission, in the TeV domain, using an empirical approach i.e. using specific statistical relations between gamma-rays (at GeV energies) and radio/X-rays properties observed in bright HBL from the literature. We compare the spectral energy distributions (SEDs) with the sensitivities of current and upcoming Cherenkov telescopes and we predict that 14 Te-REX could be detectable with 50 h of observations of CTA and 7 of them also with current Cherenkov facilities in 50 h. By extrapolating these numbers on the total extragalactic sky, we predict that about 800 HBL could be visible in pointed CTA observations and ∼400 with current Cherenkov telescopes in 50 h. Interestingly, our predictions show that a non-negligible fraction (∼30 per cent) of the HBL that will be detectable by CTA is composed of relatively weak objects whose optical nuclear emission is swamped by the host-galaxy light and not (yet) detected by Fermi-LAT.

scholarly journals Multiwavelength observations in 2019-2020 of a new very-high-energy gamma-ray emitter: the flat spectrum radio quasar QSO B1420+326

2021 ◽  
Author(s):  
Filippo D’Ammando ◽  
Roberto Angioni ◽  
Monica Orienti ◽  
Julian Sitarek ◽  
Seiya Nozaki ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
High Energy Gamma ◽  
Spectrum Radio ◽  
Very High Energy ◽  
Energy Gamma ◽  
Radio Quasar ◽  
Very High ◽  
Multiwavelength Observations
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