scholarly journals Testing two-component models on very high-energy gamma-ray-emitting BL Lac objects

2020 ◽  
Vol 640 ◽  
pp. A132
Author(s):  
◽  
V. A. Acciari ◽  
S. Ansoldi ◽  
L. A. Antonelli ◽  
A. Arbet Engels ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Component Model ◽  
Bl Lac Objects ◽  
Two Component ◽  
Very High Energy ◽  
Component Models ◽  
Very High ◽  
Optical Polarisation

Context. It has become evident that one-zone synchrotron self-Compton models are not always adequate for very high-energy (VHE) gamma-ray-emitting blazars. While two-component models perform better, they are difficult to constrain due to the large number of free parameters. Aims. In this work, we make a first attempt at taking into account the observational constraints from very long baseline interferometry (VLBI) data, long-term light curves (radio, optical, and X-rays), and optical polarisation to limit the parameter space for a two-component model and test whether or not it can still reproduce the observed spectral energy distribution (SED) of the blazars. Methods. We selected five TeV BL Lac objects based on the availability of VHE gamma-ray and optical polarisation data. We collected constraints for the jet parameters from VLBI observations. We evaluated the contributions of the two components to the optical flux by means of decomposition of long-term radio and optical light curves as well as modelling of the optical polarisation variability of the objects. We selected eight epochs for these five objects based on the variability observed at VHE gamma rays, for which we constructed the SEDs that we then modelled with a two-component model. Results. We found parameter sets which can reproduce the broadband SED of the sources in the framework of two-component models considering all available observational constraints from VLBI observations. Moreover, the constraints obtained from the long-term behaviour of the sources in the lower energy bands could be used to determine the region where the emission in each band originates. Finally, we attempt to use optical polarisation data to shed new light on the behaviour of the two components in the optical band. Our observationally constrained two-component model allows explanation of the entire SED from radio to VHE with two co-located emission regions.

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 A STRONG RADIO BRIGHTENING AT THE JET BASE OF M 87 DURING THE ELEVATED VERY HIGH ENERGY GAMMA-RAY STATE IN 2012

2014 ◽  
Vol 788 (2) ◽  
pp. 165 ◽  
Author(s):  
K. Hada ◽  
M. Giroletti ◽  
M. Kino ◽  
G. Giovannini ◽  
F. D'Ammando ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
High Energy Gamma ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

scholarly journals Future science issues for Galactic very-high-energy gamma-ray astronomy

2008 ◽  
Author(s):  
Diego F. Torres ◽  
Felix A. Aharonian ◽  
Werner Hofmann ◽  
Frank Rieger
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Gamma Ray Astronomy ◽  
High Energy Gamma ◽  
Future Science ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

BINARY PULSAR SYSTEM PSR B1259-63/LS2883 AS A GAMMA-RAY EMITTER

2014 ◽  
Vol 28 ◽  
pp. 1460169 ◽  
Author(s):  
DMITRY KHANGULYAN ◽  
SERGEY V. BOGOVALOV ◽  
FELIX A. AHARONIAN
Keyword(s):  
Energy Band ◽  
Gamma Ray ◽  
High Energy ◽  
Energy Losses ◽  
Binary Pulsar ◽  
Emission Component ◽  
Emission Enhancement ◽  
Very High Energy ◽  
Hydrodynamical Simulations ◽  
Very High

Observations of the binary pulsar PSR B1259-63/LS2883 in the high energy and very high energy domains have revealed a few quite unusual features. One of the most puzzling phenomena is the bright GeV flare detected with Fermi/LAT in 2011 January, approximately one month after periastron passage. Since the maximum luminosity in the high energy band during the flare nearly achieved the level of the pulsar spin-down energy losses, it is likely that the particles, responsible for this emission component, had a strongly anisotropic distribution, which resulted in the emission enhancement. One of the most prolific scenarios for such an emission enhancement is the Doppler boosting, which is realized in sources with relativistic motions. Interestingly, a number of hydrodynamical simulations have predicted a formation of highly relativistic outflows in binary pulsar systems, therefore scenarios, involving relativistic boosting, are very natural for these systems. However a more detailed analysis of such a possibility, presented in this study, reveals certain limitations which put strict constraints on the maximum luminosity achievable in this scenario. These constraints render the "Doppler boosting" scenario to be less feasible, especially for the synchrotron models.

VERITAS OBSERVATIONS OF RELATIVISTIC OUTFLOWS IN LOW- AND INTERMEDIATE-FREQUENCY-PEAKED BL LAC OBJECTS

2014 ◽  
Vol 28 ◽  
pp. 1460178
Author(s):  
◽  
HEIKE PROKOPH
Keyword(s):  
Gamma Ray ◽  
Intermediate Frequency ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Bl Lac ◽  
Bl Lacs ◽  
Gamma Ray Telescopes ◽  
Very High

The majority of blazars detected at very high energies (VHE; E > 100 GeV) are high-frequency-peaked BL Lac objects (HBLs). Low- and intermediate-frequency-peaked BL Lacs (LBLs/IBLs with synchrotron-peak frequencies in the infrared and optical regime) are generally more powerful, more luminous, and have a richer jet environment than HBLs. However, only a handful of these IBL and LBLs have been detected by ground-based gamma-ray telescopes, typically during high-flux states. The VERITAS array has been monitoring five known VHE LBLs/IBLs since 2009: 3C 66A, W Comae, PKS 1424+240, S5 0716+714 and BL Lacertae, with typical exposures of 5-10 hours per year. The results of these long-term observations are presented, including a bright, subhour-scale VHE flare of BL Lacertae in June 2011, the first low-state detections of 3C 66A and W Comae, and the detection and characterization of the IBL B2 1215+30.

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