Abstract
The unidentified very-high-energy (VHE;E> 0.1 TeV)γ-ray source, HESS J1826−130, was discovered with the High Energy Stereoscopic System (HESS) in the Galactic plane. The analysis of 215 h of HESS data has revealed a steadyγ-ray flux from HESS J1826−130, which appears extended with a half-width of 0.21° ± 0.02stat° ± 0.05sys°. The source spectrum is best fit with either a power-law function with a spectral index Γ = 1.78 ± 0.10stat± 0.20sysand an exponential cut-off at 15.2−3.2+5.5TeV, or a broken power-law with Γ1= 1.96 ± 0.06stat± 0.20sys, Γ2= 3.59 ± 0.69stat± 0.20sysfor energies below and aboveEbr= 11.2 ± 2.7 TeV, respectively. The VHE flux from HESS J1826−130 is contaminated by the extended emission of the bright, nearby pulsar wind nebula, HESS J1825−137, particularly at the low end of the energy spectrum. Leptonic scenarios for the origin of HESS J1826−130 VHE emission related to PSR J1826−1256 are confronted by our spectral and morphological analysis. In a hadronic framework, taking into account the properties of dense gas regions surrounding HESS J1826−130, the source spectrum would imply an astrophysical object capable of accelerating the parent particle population up to ≳200 TeV. Our results are also discussed in a multiwavelength context, accounting for both the presence of nearby supernova remnants, molecular clouds, and counterparts detected in radio, X-rays, and TeV energies.
Highlights
The High Energy Stereoscopic System (HESS) Galactic Plane Survey (HGPS) revealed the presence of 16 new γ-ray sources in the very high energy (VHE; E > 0.1 TeV) domain
The contamination from HESS J1825−137 could potentially affect the spectrum of HESS J1826−130, our studies demonstrate that the effects on the spectral parameters are at the level of our analysis systematic uncertainties
The deep observation campaign on the source reported in this paper provides several constraints to its spectral and morphological properties, its origin is still uncertain
Summary
The High Energy Stereoscopic System (HESS) Galactic Plane Survey (HGPS) revealed the presence of 16 new γ-ray sources in the very high energy (VHE; E > 0.1 TeV) domain The results obtained from the analysis of 215 h of VHE γ-ray data recorded with the HESS telescopes is presented, yielding an accurate morphological description and a detailed spectral characterization of the source, including an energy-dependent emission study of the region. Spectral analysis The green circular region with a radius of 0.22◦ centered at the best-fit position of HESS J1826−130 (see Fig. 1) was used as the integration region for measuring the differential VHE γ-ray spectrum of the source. Taking the ratio of the total number of excess counts within the integration region (Fig. 1, green circle) used for measuring HESS J1826−130’s spectrum between the model components can give a quantitative estimation of the contamination. The 3D analysis results published in Ziegler (2018) are found to be compatible with the results presented here
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