Very high-energy observations of the two high-frequency peaked BL Lac objects 1ES 1218+304 and H 1426+428

ABSTRACT We report on the detection of very high energy (VHE; E > 100 GeV) γ-ray emission from the BL Lac objects KUV 00311−1938 and PKS 1440−389 with the High Energy Stereoscopic System (H.E.S.S.). H.E.S.S. observations were accompanied or preceded by multiwavelength observations with Fermi/LAT, XRT and UVOT onboard the Swift satellite, and ATOM. Based on an extrapolation of the Fermi/LAT spectrum towards the VHE γ-ray regime, we deduce a 95 per cent confidence level upper limit on the unknown redshift of KUV 00311−1938 of $z$ < 0.98 and of PKS 1440−389 of $z$ < 0.53. When combined with previous spectroscopy results, the redshift of KUV 00311−1938 is constrained to 0.51 ≤ $z$ < 0.98 and of PKS 1440−389 to 0.14 ⪅ $z$ < 0.53.

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Very High Energy gamma-rays from blazars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314003524 ◽

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.

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Hadronic flares and associated neutrinos for Markarian 421

Proceedings of the International Astronomical Union ◽

10.1017/s174392131500215x ◽

2014 ◽

Vol 10 (S313) ◽

pp. 177-178 ◽

Cited By ~ 1

Author(s):

Antonio Marinelli ◽

Barbara Patricelli ◽

Nissim Fraija

Keyword(s):

Monte Carlo Simulation ◽

Monte Carlo ◽

Neutrino Flux ◽

High Energy ◽

Neutrino Telescope ◽

Bl Lac Objects ◽

Markarian 421 ◽

Bl Lac ◽

Very High Energy ◽

Very High

AbstractMarkarian 421 (Mrk 421) is one of the brightest, fastest and closest BL Lac objects known. Its very high energy (VHE) spectrum has been successfully modeled with both leptonic and hadronic models and no conclusive results have been achieved yet about the origin of its VHE emission. Here we investigate the possibility that a fraction of the VHE flares of Mrk 421 are due to hadronic processes and calculate the expected associated neutrino flux. We introduce the obtained neutrino flux in a Monte Carlo simulation to see the expectation for a km3 Cherenkov neutrino telescope.

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Is very high energy emission from the BL Lac 1ES 0806+524 centrifugally driven?

New Astronomy ◽

10.1016/j.newast.2009.10.001 ◽

2010 ◽

Vol 15 (4) ◽

pp. 351-355 ◽

Cited By ~ 5

Author(s):

Z. Osmanov

Keyword(s):

High Energy ◽

Energy Emission ◽

Bl Lac ◽

Very High Energy ◽

High Energy Emission ◽

Very High

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THE H.E.S.S. EXTRAGALACTIC SKY

International Journal of Modern Physics Conference Series ◽

10.1142/s201019451460163x ◽

2014 ◽

Vol 28 ◽

pp. 1460163

Author(s):

◽

JEAN-PHILIPPE LENAIN

Keyword(s):

Radio Galaxies ◽

High Energy ◽

Bl Lac Objects ◽

Dominant Class ◽

Cherenkov Telescopes ◽

Spectrum Radio ◽

System Experiment ◽

Very High Energy ◽

Stereoscopic System ◽

Very High

More than fifty extragalactic very high energy (VHE; E > 100 GeV) sources have been found using ground-based imaging atmospheric Cherenkov telescopes, about twenty of which have been discovered using the H.E.S.S. (High Energy Stereoscopic System) experiment based in Namibia. Even though BL Lac objects are the dominant class of VHE detected extragalactic objects, other types of sources (starburst galaxies, radio galaxies or flat spectrum radio quasars) begin to emerge. A review of the extragalactic sources studied with H.E.S.S. is given, with an emphasis on new results.

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037811 ◽

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.

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VHE BL Lacs through the MAGIC glasses

Proceedings of the International Astronomical Union ◽

10.1017/s174392131500188x ◽

2014 ◽

Vol 10 (S313) ◽

pp. 64-69

Author(s):

Josefa Becerra González ◽

Keyword(s):

Optical Emission ◽

Theoretical Models ◽

High Energy ◽

Bl Lac Objects ◽

Individual Object ◽

Bl Lac ◽

Multi Wavelength ◽

Very High Energy ◽

First Time

AbstractIn this contribution an overview of the latest results on the study of BL Lac objects with the MAGIC telescopes at the very high energy (VHE, E>100 GeV) gamma-rays is presented. Three new VHE sources were detected during 2014, two BL Lac objects and the gravitational lensed blazar S3 0218+357. MAGIC detected very fast intra-night variability from IC 310. This detection points to smaller emitting regions than the event horizon, this is hard to be explained in the framework of the current theoretical models. The long term multi wavelength (MWL) study of the BL Lac PKS 1424+240 shows correlation between the radio and optical emission, pointing to a common origin. The MWL SED is not well fitted by a one-zone synchrotron-self Compton (SSC) model, but a two-zone SSC model can explain both, the MWL light curve and the SED. Spectral curvature has been found in the observed VHE spectrum from PG 1553+113. This is the first time that spectral curvature compatible with the EBL absorption is found in an individual object.

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Peculiar emission from the new VHE gamma-ray source H1722+119

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317001387 ◽

2016 ◽

Vol 12 (S324) ◽

pp. 251-252

Author(s):

T. Terzić ◽

A. Stamerra ◽

F. D'Ammando ◽

C. M. Raiteri ◽

M. Villata ◽

...

Keyword(s):

High Activity ◽

Energy Band ◽

Gamma Ray ◽

High Energy ◽

Cherenkov Telescopes ◽

Bl Lac ◽

Gamma Ray Imaging ◽

Very High Energy ◽

Γ Ray ◽

Very High

The BL Lac object H1722+119 was observed in the very high energy band (VHE, E > 100 GeV) by the MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes (Aleksić et al. 2016a, b)) between 2013 May 17 and 22, following a state of high activity in the optical band measured by the KVA (Kungliga Vetenskapsakademien) telescope. Optical high states are often used to trigger MAGIC observations, which result in the VHE γ-ray signal detection (see e.g. Aleksić et al. 2015, Ahnen et al. 2016 and references therein).

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Detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832624 ◽

2018 ◽

Vol 617 ◽

pp. A30 ◽

Cited By ~ 3

Author(s):

◽

M. L. Ahnen ◽

S. Ansoldi ◽

L. A. Antonelli ◽

C. Arcaro ◽

...

Keyword(s):

Light Curve ◽

Spectral Energy Distribution ◽

Low Frequency ◽

High Energy ◽

Spectral Energy ◽

Polarization Angle ◽

Optical Polarization ◽

Bl Lac Objects ◽

Very High Energy ◽

Very High

Aims. The very high energy (VHE ≳100 GeV) γ-ray MAGIC observations of the blazar S4 0954+65, were triggered by an exceptionally high flux state of emission in the optical. This blazar has a disputed redshift of z = 0.368 or z ≥ 0.45 and an uncertain classification among blazar subclasses. The exceptional source state described here makes for an excellent opportunity to understand physical processes in the jet of S4 0954+65 and thus contribute to its classification. Methods. We investigated the multiwavelength (MWL) light curve and spectral energy distribution (SED) of the S4 0954+65 blazar during an enhanced state in February 2015 and have put it in context with possible emission scenarios. We collected photometric data in radio, optical, X-ray, and γ-ray. We studied both the optical polarization and the inner parsec-scale jet behavior with 43 GHz data. Results. Observations with the MAGIC telescopes led to the first detection of S4 0954+65 at VHE. Simultaneous data with Fermi-LAT at high energy γ-ray (HE, 100 MeV < E < 100 GeV) also show a period of increased activity. Imaging at 43 GHz reveals the emergence of a new feature in the radio jet in coincidence with the VHE flare. Simultaneous monitoring of the optical polarization angle reveals a rotation of approximately 100°. Conclusions. The high emission state during the flare allows us to compile the simultaneous broadband SED and to characterize it in the scope of blazar jet emission models. The broadband spectrum can be modeled with an emission mechanism commonly invoked for flat spectrum radio quasars (FSRQs), that is, inverse Compton scattering on an external soft photon fieldfrom the dust torus, also known as external Compton. The light curve and SED phenomenology is consistent with an interpretation of a blob propagating through a helical structured magnetic field and eventually crossing a standing shock in the jet, a scenario typically applied to FSRQs and low-frequency peaked BL Lac objects (LBL).

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