scholarly journals Very high energy γ-ray emission from two blazars of unknown redshift and upper limits on their distance

2020 ◽  
Vol 494 (4) ◽  
pp. 5590-5602
Author(s):  
H Abdalla ◽  
R Adam ◽  
F Aharonian ◽  
F Ait Benkhali ◽  
E O Angüner ◽  
...  
Keyword(s):  
Confidence Level ◽  
High Energy ◽  
Bl Lac Objects ◽  
Upper Limit ◽  
Upper Limits ◽  
Bl Lac ◽  
Very High Energy ◽  
Stereoscopic System ◽  
Γ Ray ◽  
Very High

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.

scholarly journals THE H.E.S.S. EXTRAGALACTIC SKY

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.

scholarly journals Very high energy observations of the BL Lac objects 3C 66A and OJ 287

2007 ◽  
Vol 28 (3) ◽  
pp. 338-347 ◽  
Author(s):  
T. Lindner ◽  
D.S. Hanna ◽  
J. Kildea ◽  
J. Ball ◽  
D.A. Bramel ◽  
...  
Keyword(s):  
High Energy ◽  
Bl Lac Objects ◽  
Bl Lac ◽  
Very High Energy ◽  
Very High

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

2011 ◽  
Vol 34 (9) ◽  
pp. 674-678 ◽  
Author(s):  
C. Mueller ◽  
N. Akhter ◽  
J. Ball ◽  
D.A. Bramel ◽  
J. Carson ◽  
...  
Keyword(s):  
High Frequency ◽  
High Energy ◽  
Bl Lac Objects ◽  
Bl Lac ◽  
Very High Energy ◽  
Very High

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

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).

scholarly journals HESS upper limit on the very high energy γ-ray emission from the globular cluster 47 Tucanae

2009 ◽  
Vol 499 (1) ◽  
pp. 273-277 ◽  
Author(s):  
F. Aharonian ◽  
A. G. Akhperjanian ◽  
G. Anton ◽  
U. Barres de Almeida ◽  
A. R. Bazer-Bachi ◽  
...  
Keyword(s):  
Globular Cluster ◽  
High Energy ◽  
Upper Limit ◽  
Very High Energy ◽  
Γ Ray ◽  
Very High

scholarly journals Hadronic flares and associated neutrinos for Markarian 421

2014 ◽  
Vol 10 (S313) ◽  
pp. 177-178 ◽  
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.

scholarly journals TeV γ-ray source MGRO J2019+37 : PWN or SNR?

2013 ◽  
Vol 9 (S296) ◽  
pp. 300-304
Author(s):  
Lab Saha ◽  
Pijushpani Bhattacharjee
Keyword(s):  
Crab Nebula ◽  
High Energy ◽  
Emission Region ◽  
Pulsar Wind Nebulae ◽  
Upper Limit ◽  
Multi Wavelength ◽  
Very High Energy ◽  
Hadronic Energy ◽  
Γ Ray ◽  
Very High

AbstractMilagro has recently reported an extended TeV γ-ray source MGRO J2019+37 in the Cygnus region. It is the second brightest TeV source after Crab nebula in their source catalogue. No confirmed counterparts of this source are known although possible associations with several known sources have been suggested. We study leptonic as well as hadronic models of TeV emission within the context of Pulsar Wind Nebulae (PWN) and Supernova Remnant (SNR) type sources, using constraints from multi-wavelength data from observations made on sources around MGRO J2019+37. These include radio upper limit given by GMRT, GeV observations by Fermi-LAT, EGRET and AGILE and very high energy data taken from Milagro. We find that, within the PWN scenario, while both leptonic as well as hadronic models can explain the TeV flux from this source, the GMRT upper limit imposes a stringent upper limit on the size of the emission region in the case of leptonic model. In the SNR scenario, on the other hand, a purely leptonic origin of TeV flux is inconsistent with the GMRT upper limit. At the same time, a dominantly hadronic origin of the TeV flux is consistent with all observations, and the required hadronic energy budget is comparable to that of typical supernovae explosions.

scholarly journals Detection of variable VHE γ-ray emission from the extra-galactic γ-ray binary LMC P3

2018 ◽  
Vol 610 ◽  
pp. L17 ◽  
Author(s):  
◽  
H. Abdalla ◽  
A. Abramowski ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
...  
Keyword(s):  
Binary System ◽  
Orbital Period ◽  
Statistical Significance ◽  
Large Magellanic Cloud ◽  
High Energy ◽  
Data Set ◽  
Very High Energy ◽  
Stereoscopic System ◽  
Γ Ray ◽  
Very High

Context. Recently, the high-energy (HE, 0.1–100 GeV) γ-ray emission from the object LMC P3 in the Large Magellanic Cloud (LMC) has been discovered to be modulated with a 10.3-day period, making it the first extra-galactic γ-ray binary. Aim. This work aims at the detection of very-high-energy (VHE, >100 GeV) γ-ray emission and the search for modulation of the VHE signal with the orbital period of the binary system. Methods. LMC P3 has been observed with the High Energy Stereoscopic System (H.E.S.S.); the acceptance-corrected exposure time is 100 h. The data set has been folded with the known orbital period of the system in order to test for variability of the emission. Results. VHE γ-ray emission is detected with a statistical significance of 6.4 σ. The data clearly show variability which is phase-locked to the orbital period of the system. Periodicity cannot be deduced from the H.E.S.S. data set alone. The orbit-averaged luminosity in the 1–10 TeV energy range is (1.4 ± 0.2) × 1035 erg s−1. A luminosity of (5 ± 1) × 1035 erg s−1 is reached during 20% of the orbit. HE and VHE γ-ray emissions are anti-correlated. LMC P3 is the most luminous γ-ray binary known so far.

scholarly journals H.E.S.S. Follow-up Observations of Binary Black Hole Coalescence Events during the Second and Third Gravitational-wave Observing Runs of Advanced LIGO and Advanced Virgo

2021 ◽  
Vol 923 (1) ◽  
pp. 109
Author(s):  
H. Abdalla ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
E. O. Angüner ◽  
H. Ashkar ◽  
...  
Keyword(s):  
Black Hole ◽  
Gravitational Wave ◽  
High Energy ◽  
Binary Black Hole ◽  
Upper Limits ◽  
Very High Energy ◽  
Stereoscopic System ◽  
The Times ◽  
Very High

Abstract We report on the observations of four well-localized binary black hole (BBH) mergers by the High Energy Stereoscopic System (H.E.S.S.) during the second and third observing runs of Advanced LIGO and Advanced Virgo, O2 and O3. H.E.S.S. can observe 20 deg2 of the sky at a time and follows up gravitational-wave (GW) events by “tiling” localization regions to maximize the covered localization probability. During O2 and O3, H.E.S.S. observed large portions of the localization regions, between 35% and 75%, for four BBH mergers (GW170814, GW190512_180714, GW190728_064510, and S200224ca). For these four GW events, we find no significant signal from a pointlike source in any of the observations, and we set upper limits on the very high energy (>100 GeV) γ-ray emission. The 1–10 TeV isotropic luminosity of these GW events is below 1045 erg s−1 at the times of the H.E.S.S. observations, around the level of the low-luminosity GRB 190829A. Assuming no changes are made to how follow-up observations are conducted, H.E.S.S. can expect to observe over 60 GW events per year in the fourth GW observing run, O4, of which eight would be observable with minimal latency.

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