Aim.
We aim for an understanding of the morphological and spectral properties of the supernova remnant RCW 86 and for insights into the production mechanism leading to the RCW 86 very high-energy
γ
...-ray emission.
Methods.
We analyzed High Energy Spectroscopic System (H.E.S.S.) data that had increased sensitivity compared to the observations presented in the RCW 86 H.E.S.S. discovery publication. Studies of the morphological correlation between the 0.5–1 keV X-ray band, the 2–5 keV X-ray band, radio, and
γ
-ray emissions have been performed as well as broadband modeling of the spectral energy distribution with two different emission models.
Results.
We present the first conclusive evidence that the TeV
γ
-ray emission region is shell-like based on our morphological studies. The comparison with 2–5 keV X-ray data reveals a correlation with the 0.4–50 TeV
γ
-ray emission. The spectrum of RCW 86 is best described by a power law with an exponential cutoff at
E
cut
= (3.5 ± 1.2
stat
) TeV and a spectral index of Γ ≈ 1.6 ± 0.2. A static leptonic one-zone model adequately describes the measured spectral energy distribution of RCW 86, with the resultant total kinetic energy of the electrons above 1 GeV being equivalent to ~0.1% of the initial kinetic energy of a Type Ia supernova explosion (10
51
erg). When using a hadronic model, a magnetic field of
B
≈ 100
μ
G is needed to represent the measured data. Although this is comparable to formerly published estimates, a standard E
−2
spectrum for the proton distribution cannot describe the
γ
-ray data. Instead, a spectral index of Γ
p
≈ 1.7 would be required, which implies that ∼7 × 10
49
/
n
cm
−3
has been transferred into high-energy protons with the effective density
n
cm
−3
=
n
/1 cm
−3
. This is about 10% of the kinetic energy of a typical Type Ia supernova under the assumption of a density of 1 cm
−3
.
Using the High Energy Spectroscopic System (H.E.S.S.) telescopes we have discovered a steady and extended very high-energy (VHE) γ-ray source towards the luminous blue variable candidate LBV 1806−20, ...massive stellar cluster Cl* 1806−20, and magnetar SGR 1806−20. The new VHE source, HESS J1808−204, was detected at a statistical significance of >6σ (post-trial) with a photon flux normalisation (2.9 ± 0.4stat ± 0.5sys) × 10−13 ph cm−2 s−1 TeV−1 at 1 TeV and a power-law photon index of 2.3 ± 0.2stat ± 0.3sys. The luminosity of this source (0.2 to 10 TeV; scaled to distance d = 8.7 kpc) is LVHE ~ 1.6 × 1034(d/8.7 kpc)2 erg s−1. The VHE γ-ray emission is extended and is well fit by a single Gaussian with statistical standard deviation of 0.095° ± 0.015°. This extension is similar to that of the synchrotron radio nebula G10.0−0.3, which is thought to be powered by LBV 1806−20. The VHE γ-ray luminosity could be provided by the stellar wind luminosity of LBV 1806−20 by itself and/or the massive star members of Cl* 1806−20. Alternatively, magnetic dissipation (e.g. via reconnection) from SGR 1806−20 can potentially account for the VHE luminosity. The origin and hadronic and/or leptonic nature of the accelerated particles responsible for HESS J1808−204 is not yet clear. If associated with SGR 1806−20, the potentially young age of the magnetar (650 yr) can be used to infer the transport limits of these particles to match the VHE source size. This discovery provides new interest in the potential for high-energy particle acceleration from magnetars, massive stars, and/or stellar clusters.
The results of follow-up observations of the TeV γ-ray source HESS J1640−465 from 2004 to 2011 with the High Energy Stereoscopic System (HESS) are reported in this work. The spectrum is well ...described by an exponential cut-off power law with photon index Γ = 2.11 ± 0.09stat ± 0.10sys, and a cut-off energy of
TeV. The TeV emission is significantly extended and overlaps with the northwestern part of the shell of the SNR G338.3−0.0. The new HESS results, a re-analysis of archival XMM-Newton data and multiwavelength observations suggest that a significant part of the γ-ray emission from HESS J1640−465 originates in the supernova remnant shell. In a hadronic scenario, as suggested by the smooth connection of the GeV and TeV spectra, the product of total proton energy and mean target density could be as high as W
p
n
H ∼ 4 × 1052(d/10kpc)2 erg cm−3.
A deep observation campaign carried out by the High Energy Stereoscopic System (HESS) on Centaurus A enabled the discovery of γ-rays from the blazar 1ES 1312−423, 2° away from the radio galaxy. With ...a differential flux at 1 TeV of φ(1 TeV) = (1.9 ± 0.6stat ± 0.4sys) × 10−13 cm−2 s−1 TeV−1 corresponding to 0.5 per cent of the Crab nebula differential flux and a spectral index Γ = 2.9 ± 0.5stat ± 0.2sys, 1ES 1312−423 is one of the faintest sources ever detected in the very high energy (E > 100 GeV) extragalactic sky. A careful analysis using three and a half years of Fermi Large Area Telescope (Fermi-LAT) data allows the discovery at high energies (E > 100 MeV) of a hard spectrum (Γ = 1.4 ± 0.4stat ± 0.2sys) source coincident with 1ES 1312−423. Radio, optical, UV and X-ray observations complete the spectral energy distribution of this blazar, now covering 16 decades in energy. The emission is successfully fitted with a synchrotron self-Compton model for the non-thermal component, combined with a blackbody spectrum for the optical emission from the host galaxy.
The non-thermal nature of the X-ray emission from the shell-type supernova remnants (SNRs) G1.9+0.3 and G330.2+1.0 is an indication of intense particle acceleration in the shock fronts of both ...objects. This suggests that the SNRs are prime candidates for very-high-energy (VHE; E > 0.1 TeV) γ-ray observations. G1.9+0.3, recently established as the youngest known SNR in the Galaxy, also offers a unique opportunity to study the earliest stages of SNR evolution in the VHE domain. The purpose of this work is to probe the level of VHE γ-ray emission from both SNRs and use this to constrain their physical properties. Observations were conducted with the H.E.S.S. (High Energy Stereoscopic System) Cherenkov Telescope Array over a more than six-year period spanning 2004–2010. The obtained data have effective livetimes of 67 h for G1.9+0.3 and 16 h for G330.2+1.0. The data are analysed in the context of the multiwavelength observations currently available and in the framework of both leptonic and hadronic particle acceleration scenarios. No significant γ-ray signal from G1.9+0.3 or G330.2+1.0 was detected. Upper limits (99 per cent confidence level) to the TeV flux from G1.9+0.3 and G330.2+1.0 for the assumed spectral index Γ = 2.5 were set at 5.6 × 10−13 cm−2 s−1 above 0.26 TeV and 3.2 × 10−12 cm−2 s−1 above 0.38 TeV, respectively. In a one-zone leptonic scenario, these upper limits imply lower limits on the interior magnetic field to B
G1.9 ≳ 12 μG for G1.9+0.3 and to B
G330 ≳ 8 μG for G330.2+1.0. In a hadronic scenario, the low ambient densities and the large distances to the SNRs result in very low predicted fluxes, for which the H.E.S.S. upper limits are not constraining.
The non-thermal nature of the X-ray emission from the shell-type supernova remnants (SNRs) G1.9+0.3 and G330.2+1.0 is an indication of intense particle acceleration in the shock fronts of both ...objects. This suggests that the SNRs are prime candidates for very-high-energy (VHE; E > 0.1 TeV) γ-ray observations. G1.9+0.3, recently established as the youngest known SNR in the Galaxy, also offers a unique opportunity to study the earliest stages of SNR evolution in the VHE domain. The purpose of this work is to probe the level of VHE γ-ray emission from both SNRs and use this to constrain their physical properties. Observations were conducted with the H.E.S.S. (High Energy Stereoscopic System) Cherenkov Telescope Array over a more than six-year period spanning 2004-2010. The obtained data have effective livetimes of 67 h for G1.9+0.3 and 16 h for G330.2+1.0. The data are analysed in the context of the multiwavelength observations currently available and in the framework of both leptonic and hadronic particle acceleration scenarios. No significant γ-ray signal from G1.9+0.3 or G330.2+1.0 was detected. Upper limits (99 per cent confidence level) to the TeV flux from G1.9+0.3 and G330.2+1.0 for the assumed spectral index ... = 2.5 were set at 5.6 x 10^sup -13^ cm^sup -2^ s^sup -1^ above 0.26 TeV and 3.2 x 10^sup -12^ cm^sup -2^ s^sup -1^ above 0.38 TeV, respectively. In a one-zone leptonic scenario, these upper limits imply lower limits on the interior magnetic field to B^sub G1.9^ ... 12 μG for G1.9+0.3 and to B^sub G330^ ... 8 μG for G330.2+1.0. In a hadronic scenario, the low ambient densities and the large distances to the SNRs result in very low predicted fluxes, for which the H.E.S.S. upper limits are not constraining. (ProQuest: ... denotes formulae/symbols omitted.)
A deep observation campaign carried out by the High Energy Stereoscopic System (HESS) on Centaurus A enabled the discovery of ...-rays from the blazar 1ES 1312...423, 2... away from the radio galaxy. ...With a differential flux at 1 TeV of ...(1 TeV) = (1.9 ± 0.6... ± 0.4...) x 10... cm... s... TeV... corresponding to 0.5 per cent of the Crab nebula differential flux and a spectral index ... = 2.9 ± 0.5... ± 0.2..., 1ES 1312 423 is one of the faintest sources ever detected in the very high energy (E > 100 GeV) extragalactic sky. A careful analysis using three and a half years of Fermi Large Area Telescope (Fermi-LAT) data allows the discovery at high energies (E > 100 MeV) of a hard spectrum (... = 1.4 ± 0.4... ± 0.2...) source coincident with 1ES 1312...423. Radio, optical, UV and X-ray observations complete the spectral energy distribution of this blazar, now covering 16 decades in energy. The emission is successfully fitted with a synchrotron self-Compton model for the non-thermal component, combined with a blackbody spectrum for the optical emission from the host galaxy. (ProQuest: ... denotes formulae/symbols omitted.)
The H.E.S.S. cameras require a precise and regular calibration over time, to reconstruct the gamma-ray characteristics. The different sub-systems used to determine the gain and the uniformity of the ...PMTs and their evolution with time are presented. Then, we focus on the absolute energy scale calibration, by using a full reconstruction of isolated muons recorded during normal observation. The method and the evolution of the absolute overall light collection efficiency are shown.
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