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 RESULTS FROM H.E.S.S. OBSERVATIONS OF RELATIVISTIC SOURCES

2010 ◽  
Vol 19 (06) ◽  
pp. 1013-1022
Author(s):  
◽  
ULISSES BARRES DE ALMEIDA
Keyword(s):  
Binary Systems ◽  
Gamma Ray ◽  
High Energy ◽  
General Picture ◽  
Cherenkov Telescopes ◽  
Invaluable Tool ◽  
Very High Energy ◽  
Energy Gamma ◽  
Stereoscopic System ◽  
Very High

The High Energy Stereoscopic System (H.E.S.S.) is a southern hemisphere array of four Imaging Atmospheric Cherenkov Telescopes observing the sky in the very-high energy gamma-ray range (E > 100 GeV ). VHE observations are an invaluable tool to study the acceleration and propagation of energetic particles in many astrophysical systems where relativistic outflows are the main drivers of the emission, such as AGNs and galactic binary systems. In this paper the main results of the H.E.S.S. observations of these objects will be reviewed, and the general picture that emerges from them will be presented. We will also comment on prospects for future investigations with H.E.S.S.-II.

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 Less noticeable shallow decay phase in early X-ray afterglows of GeV/TeV-detected gamma-ray bursts

2020 ◽  
Vol 494 (4) ◽  
pp. 5259-5269 ◽  
Author(s):  
Ryo Yamazaki ◽  
Yuri Sato ◽  
Takanori Sakamoto ◽  
Motoko Serino
Keyword(s):  
Power Law ◽  
Gamma Ray ◽  
High Energy ◽  
Decay Phase ◽  
Power Law Model ◽  
X Ray ◽  
High Energy Gamma ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

ABSTRACT The nature of the shallow decay phase in the X-ray afterglow of the gamma-ray burst (GRB) is not yet clarified. We analyse the data of early X-ray afterglows of 26 GRBs triggered by Burst Alert Telescope onboard Neil Gehrels Swift Observatory and subsequently detected by Fermi Large Area Telescope (LAT) and/or Imaging Atmospheric Cherenkov Telescopes. It is found that nine events (including two out of three very-high-energy gamma-ray events) have no shallow decay phase and that their X-ray afterglow light curves are well described by single power-law model except for the jet break at later epoch. The rest are fitted by double power-law model and have a break in the early epoch (around ks), however, eight events (including a very-high-energy gamma-ray event) have the pre-break decay index larger than 0.7. We also analyse the data of well-sampled X-ray afterglows of GRBs without LAT detection and compare their decay properties with those of high-energy and very-high-energy gamma-ray events. It is found that for the GeV/TeV bursts, the fraction of events whose X-ray afterglows are described by single power law is significantly larger than those for non-GeV/TeV GRBs. Even if the GeV/TeV GRBs have shallow decay phase, their decay slope tends to be steeper than non-GeV/TeV bursts, that is, they have less noticeable shallow decay phase in the early X-ray afterglow. A possible interpretation along with the energy injection model is briefly discussed.

scholarly journals Discovery of very-high-energy gamma-ray emission from a hard-X-ray bright HBL RX J1136.5+6737

2016 ◽  
Author(s):  
Masaaki Hayashida ◽  
Hajime Takami ◽  
Yusuke Konno ◽  
Ryosuke ITOH
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
X Ray ◽  
High Energy Gamma ◽  
Very High Energy ◽  
Energy Gamma ◽  
Gamma Ray Emission ◽  
Very High

scholarly journals Empirical multi-wavelength prediction method for Very High Energy Gamma-ray emitting BL Lacs

2016 ◽  
Vol 12 (S324) ◽  
pp. 239-240
Author(s):  
V. Fallah Ramazani ◽  
E. Lindfors ◽  
K. Nilsson
Keyword(s):  
Gamma Ray ◽  
Prediction Method ◽  
High Energy ◽  
Linear Regression Method ◽  
Cherenkov Telescopes ◽  
Multi Wavelength ◽  
Very High Energy ◽  
Energy Gamma ◽  
Bl Lacs ◽  
Very High

AbstractWe present the most up-to-date and complete multi-wavelength correlation analysis on luminosity properties of TeV BL Lacs. Correlation function (power law or linear) parameters are calculated based on linear regression method. Using the lower energy luminosities of a sample of 182 non-TeV BL Lacs and the generated functions, minimum level of VHE gamma-ray emission was calculated for each non-TeV BL Lacs. This multi wavelength prediction method gives us a list of best candidates to be observed with current generation of Imaging Air Cherenkov Telescopes.

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