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.

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 Magnetic energy dissipation and origin of non-thermal spectra in radiatively efficient relativistic sources

2019 ◽  
Vol 491 (3) ◽  
pp. 3900-3907 ◽  
Author(s):  
E Sobacchi ◽  
Y E Lyubarsky
Keyword(s):  
Energy Distribution ◽  
Magnetic Energy ◽  
Strong Electric Field ◽  
Spectral Energy Distribution ◽  
Lorentz Factor ◽  
High Energy ◽  
Local Magnetic Field ◽  
Spectral Energy ◽  
Electron Mass ◽  
Electron Positron

ABSTRACT The dissipation of turbulent magnetic fields is an appealing scenario to explain the origin of non-thermal particles in high-energy astrophysical sources. However, it has been suggested that the particle distribution may effectively thermalize when the radiative (synchrotron and/or Inverse Compton) losses are severe. Inspired by recent particle-in-cell simulations of relativistic turbulence, which show that electrons are impulsively heated in intermittent current sheets by a strong electric field aligned with the local magnetic field, we instead argue that in plasmas where the particle number density is dominated by the pairs (electron–positron and electron–positron–ion plasmas): (i) as an effect of fast cooling and of different injection times, the electron energy distribution is dne/dγ ∝ γ−2 for γ ≲ γheat (the Lorentz factor γheat being close to the equipartition value), while the distribution steepens at higher energies; (ii) since the time-scales for the turbulent fields to decay and for the photons to escape are of the same order, the magnetic and the radiation energy densities in the dissipation region are comparable; (iii) if the mass energy of the plasma is dominated by the ion component, the pairs with a Lorentz factor smaller than a critical one (of the order of the proton-to-electron mass ratio) become isotropic, while the pitch angle remains small otherwise. The outlined scenario is consistent with the typical conditions required to reproduce the spectral energy distribution of blazars, and allows one to estimate the magnetization of the emission site. Finally, we show that turbulence within the Crab Nebula may power the observed gamma-ray flares if the pulsar wind is nearly charge separated at high latitudes.

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 Monitoring of the radio galaxy M 87 at Very High Energy with MAGIC during a low emission state between 2012 and 2015

2016 ◽  
Vol 12 (S324) ◽  
pp. 164-167
Author(s):  
C. Arcaro ◽  
P. Bangale ◽  
M. Manganaro ◽  
D. Mazin ◽  
P. Colin ◽  
...  
Keyword(s):  
Radio Galaxy ◽  
Spectral Energy Distribution ◽  
Photon Emission ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
Low Emission ◽  
Very High Energy ◽  
Alternative Scenarios ◽  
Very High

AbstractWe present the preliminary results from observing the nearby radio galaxy M 87 for 156 hours (between the years 2012 and 2015) with the MAGIC telescopes, which lead to a significant very high energy (VHE, E > 100 GeV) detection of the source in quiescent states each year. Our VHE analysis combined with quasi-simultaneous data at other energies (from gamma-rays, X-rays, optical and radio) provides a unique opportunity to study the source variability and its broadband spectral energy distribution, which is found to disfavour a one-zone synchrotron/synchrotron self-Compton model. Therefore, other alternative scenarios for the photon emission are explored. We also find that the VHE emission is compatible with being produced close to the source radio core as previous data already indicated. A detailed paper presenting full results of the observing campaign is in preparation.

scholarly journals An intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced state

2020 ◽  
Vol 496 (3) ◽  
pp. 3912-3928
Author(s):  
MAGIC Collaboration: V A Acciari ◽  
S Ansoldi ◽  
L A Antonelli ◽  
A Arbet Engels ◽  
A Babić ◽  
...  
Keyword(s):  
Crab Nebula ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
Bl Lac ◽  
Very High Energy ◽  
Γ Ray ◽  
Using Data ◽  
The Crab Nebula

ABSTRACT Extreme high-frequency BL Lacs (EHBL) feature their synchrotron peak of the broad-band spectral energy distribution (SED) at νs ≥ 1017 Hz. The BL Lac object 1ES 2344+514 was included in the EHBL family because of its impressive shift of the synchrotron peak in 1996. During the following years, the source appeared to be in a low state without showing any extreme behaviours. In 2016 August, 1ES 2344+514 was detected with the ground-based γ-ray telescope FACT during a high γ-ray state, triggering multiwavelength (MWL) observations. We studied the MWL light curves of 1ES 2344+514 during the 2016 flaring state, using data from radio to very-high-energy (VHE) γ-rays taken with OVRO, KAIT, KVA, NOT, some telescopes of the GASP-WEBT collaboration at the Teide, Crimean, and St. Petersburg observatories, Swift-UVOT, Swift-XRT, Fermi-LAT, FACT, and MAGIC. With simultaneous observations of the flare, we built the broad-band SED and studied it in the framework of a leptonic and a hadronic model. The VHE γ-ray observations show a flux level of 55 per cent of the Crab Nebula flux above 300 GeV, similar to the historical maximum of 1995. The combination of MAGIC and Fermi-LAT spectra provides an unprecedented characterization of the inverse-Compton peak for this object during a flaring episode. The Γ index of the intrinsic spectrum in the VHE γ-ray band is 2.04 ± 0.12stat ± 0.15sys. We find the source in an extreme state with a shift of the position of the synchrotron peak to frequencies above or equal to 1018 Hz.

scholarly journals A NuSTAR view of powerful γ-ray loud blazars

2019 ◽  
Vol 627 ◽  
pp. A72 ◽  
Author(s):  
G. Ghisellini ◽  
M. Perri ◽  
L. Costamante ◽  
G. Tagliaferri ◽  
T. Sbarrato ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Peak Frequency ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
X Ray ◽  
Γ Ray ◽  
The Universe ◽  
Jet Power

We observed three blazars at z >  2 with the NuSTAR satellite. These were detected in the γ-rays by Fermi/LAT and in the soft X-rays, but have not yet been observed above 10 keV. The flux and slope of their X-ray continuum, together with Fermi/LAT data allows us to estimate their total electromagnetic output and peak frequency. For some of them we were able to study the source in different states, and investigate the main cause of the different observed spectral energy distribution. We then collected all blazars at redshifts greater than 2 observed by NuSTAR, and confirm that these hard and luminous X-ray blazars are among the most powerful persistent sources in the Universe. We confirm the relation between the jet power and the disk luminosity, extending it at the high-energy end.

scholarly journals THE FSRQs 3C 279 AND PKS 1510-089: MAGIC LATEST RESULTS AND MULTIWAVELENGTH OBSERVATIONS

2014 ◽  
Vol 28 ◽  
pp. 1460176 ◽  
Author(s):  
◽  
G. DE CANEVA ◽  
U. BARRES DE ALMEIDA ◽  
E. LINDFORS ◽  
K. SAITO ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
Spectrum Radio ◽  
Upper Limits ◽  
Very High Energy ◽  
Γ Rays ◽  
Differential Flux ◽  
Multiwavelength Observations

At very high energy (VHE, E> 100 GeV), we count only three blazars of the flat spectrum radio quasars (FSRQs) type to date. The MAGIC experiment detected all three of them; here we present MAGIC observations of 3C 279 and PKS 1510-089. 3C 279 was observed in 2011, without a significant detection, hence upper limits on the differential flux have been computed. The MAGIC observations of PKS 1510-089 in 2012 were triggered by alerts of high activity states and resulted in a significant detection. MAGIC observations are complemented with simultaneous multiwavelength observations in high energy γ rays, X-rays, optical and radio wavelengths and polarization measurements. With the study of the spectral features and the variability observed, we aim to identify the physical processes responsible for the behavior of this source class. In particular, we propose coherent scenarios, which take into account both the modeling of the spectral energy distribution and the constraints obtained from the lightcurves.

scholarly journals VERY HIGH ENERGY GAMMA RAYS FROM e± PAIR HALOS

2009 ◽  
Vol 18 (06) ◽  
pp. 911-927 ◽  
Author(s):  
A. EUNGWANICHAYAPANT ◽  
F. AHARONIAN
Keyword(s):  
Energy Spectrum ◽  
Gamma Rays ◽  
High Energy ◽  
Angular Distributions ◽  
Extragalactic Background Light ◽  
Electron Positron ◽  
Very High Energy ◽  
Energy Gamma ◽  
Electron Positron Pair ◽  
Very High

In this paper we study the formation of giant electron–positron pair halos around the powerful high energy extragalactic sources. We investigate the dependence of radiation of pair halos, in particular the spectral and angular distributions on the energy spectrum of the primary gamma rays, the redshift of the source, and the flux of the extragalactic background light.

scholarly journals IGR J17503–2636: a candidate supergiant fast X-ray transient

2019 ◽  
Vol 624 ◽  
pp. A142 ◽  
Author(s):  
C. Ferrigno ◽  
E. Bozzo ◽  
A. Sanna ◽  
G. K. Jaisawal ◽  
J. M. Girard ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Neutron Star ◽  
Energy Distribution ◽  
Power Law ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
X Ray ◽  
Broad Feature

The object IGR J17503–2636 is a hard X-ray transient discovered by INTEGRAL on 2018 August 11. This was the first ever reported X-ray emission from this source. Following the discovery, follow-up observations were carried out with Swift, Chandra, NICER, and NuSTAR. Here we report on the analysis of all of these X-ray data and the results obtained. Based on the fast variability in the X-ray domain, the spectral energy distribution in the 0.5–80 keV energy range, and the reported association with a highly reddened OB supergiant at ∼10 kpc, we conclude that IGR J17503–2636 is most likely a relatively faint new member of the supergiant fast X-ray transients. Spectral analysis of the NuSTAR data revealed a broad feature in addition to the typical power-law with exponential roll-over at high energy. This can be modeled either in emission or as a cyclotron scattering feature in absorption. If confirmed by future observations, this feature would indicate that IGR J17503–2636 hosts a strongly magnetized neutron star with B ∼ 2 × 1012 G.

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