scholarly journals Gamma-ray emission in radio galaxies, from MeV to TeV

2018 ◽  
Vol 14 (S342) ◽  
pp. 158-166
Author(s):  
Eleonora Torresi
Keyword(s):  
Gamma Ray ◽  
Radio Galaxies ◽  
High Energy ◽  
Cherenkov Telescopes ◽  
New Class ◽  
Very High Energy ◽  
Structure Complexity ◽  
The Impact ◽  
Jet Structure ◽  
Very High

AbstractThanks to the Fermi λ-ray satellite and the current Imaging Atmospheric Cherenkov Telescopes, radio galaxies have arisen as a new class of high- and very-high energy emitters. The favourable orientation of their jets makes radio galaxies extremely relevant in addressing important issues such as: (i) revealing the jet structure complexity; (ii) localising the emitting region(s) of high- and very-high energy radiation; (iii) understanding the physical processes producing these photons. In this review the main results on the λ-ray emission studies of radio galaxies from the MeV to TeV regimes will be presented, and the impact of future Cherenkov Telescope Array observations will be discussed.

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 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 Search for High Energy emission from GRBs with MAGIC

2016 ◽  
Vol 12 (S324) ◽  
pp. 70-73
Author(s):  
Alessio Berti ◽  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Cherenkov Telescopes ◽  
Gamma Ray Imaging ◽  
Very High Energy ◽  
Γ Rays ◽  
High Energy Emission ◽  
The Universe ◽  
Very High

AbstractGamma-Ray Bursts (GRBs) are the most violent explosions in the Universe, releasing a huge amount of energy in few seconds. While our understanding of the prompt and the afterglow phases has increased with Swift and Fermi, we have very few information about their High Energy (HE, E ≲ 100) emission components. This requires a ground-based experiment able to perform fast follow-up with enough sensitivity above ~ 50 GeV. The MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes have been designed to perform fast follow-up on GRBs thanks to fast slewing movement and low energy threshold (~ 50 GeV). Since the beginning of the operations, MAGIC followed-up 89 GRBs in good observational conditions. In this contribution the MAGIC GRBs follow-up campaign and the results which could be obtained by detecting HE and Very High Energy (VHE, E ≳ 100 GeV) γ-rays from GRBs will be reviewed.

scholarly journals The Crab Pulsar and Nebula as Seen in Gamma-Rays

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 448
Author(s):  
Elena Amato ◽  
Barbara Olmi
Keyword(s):  
Gamma Ray ◽  
Crab Nebula ◽  
High Energy ◽  
Crab Pulsar ◽  
Gamma Ray Astronomy ◽  
Very High Energy ◽  
Energy Gamma ◽  
The Crab Nebula ◽  
The Impact ◽  
Very High

Slightly more than 30 years ago, Whipple detection of the Crab Nebula was the start of Very High Energy gamma-ray astronomy. Since then, gamma-ray observations of this source have continued to provide new surprises and challenges to theories, with the detection of fast variability, pulsed emission up to unexpectedly high energy, and the very recent detection of photons with energy exceeding 1 PeV. In this article, we review the impact of gamma-ray observations on our understanding of this extraordinary accelerator.

VERITAS: STATUS SUMMARY 2009

2010 ◽  
Vol 19 (06) ◽  
pp. 1003-1012 ◽  
Author(s):  
◽  
T. C. WEEKES ◽  
V. A. ACCIARI ◽  
T. ARLEN ◽  
T. AUNE ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Reliability ◽  
High Energy ◽  
Telescope Array ◽  
Cherenkov Telescopes ◽  
The Status ◽  
Very High Energy ◽  
Very High

VERITAS is a ground-based gamma-ray observatory that uses the imaging atmospheric Cherenkov technique and operates in the very-high energy (VHE) region of the gamma-ray spectrum from 100 GeV to 50 TeV. The observatory consists of an array of four 12 m-diameter imaging atmospheric Cherenkov telescopes located in southern Arizona, USA. The four-telescope array has been fully operational since September 2007, and over the last two years, VERITAS has been operating with high reliability and sensitivity. It is currently one of the most sensitive VHE observatories. This paper summarizes the status of VERITAS as of October 2009, and describes the detection of several new VHE gamma-ray sources.

scholarly journals Gamma-ray burst detection prospects for next generation ground-based VHE facilities

2021 ◽  
Author(s):  
G La Mura ◽  
U Barres de Almeida ◽  
R Conceição ◽  
A De Angelis ◽  
F Longo ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Large Area ◽  
Gamma Ray Burst ◽  
Cherenkov Telescopes ◽  
200 Gev ◽  
Energy Domain ◽  
Very High Energy ◽  
Γ Ray ◽  
Very High

Abstract Gamma-ray Bursts (GRB) were discovered by satellite-based detectors as powerful sources of transient γ-ray emission. The Fermi satellite detected an increasing number of these events with its dedicated Gamma-ray Burst Monitor (GBM), some of which were associated with high energy photons (E > 10 GeV), by the Large Area Telescope (LAT). More recently, follow-up observations by Cherenkov telescopes detected very high energy emission (E > 100 GeV) from GRBs, opening up a new observational window with implications on the interpretation of their central engines and on the propagation of very energetic photons across the Universe. Here, we use the data published in the 2nd Fermi-LAT Gamma Ray Burst Catalogue to characterise the duration, luminosity, redshift and light curve of the high energy GRB emission. We extrapolate these properties to the very high energy domain, comparing the results with available observations and with the potential of future instruments. We use observed and simulated GRB populations to estimate the chances of detection with wide-eld ground-based γ-ray instruments. Our analysis aims to evaluate the opportunities of the Southern Wide-eld-of-view Gamma-ray Observatory (SWGO), to be installed in the Southern Hemisphere, to complement CTA. We show that a low-energy observing threshold (Elow < 200 GeV), with good point source sensitivity (Flim ≈ 10−11erg cm−2 s−1 in 1 yr), are optimal requirements to work as a GRB trigger facility and to probe the burst spectral properties down to time scales as short as 10 s, accessing a time domain that will not be available to IACT instruments.

Sign in / Sign up

Export Citation Format

Share Document