HESS VHE Gamma-Ray Sources Without Identified Counterparts

TL;DR

This paper analyzes unidentified very-high-energy gamma-ray sources detected by HESS in the Galactic plane, presenting their spectra and sky maps, and finding no plausible counterparts in other wavelengths, to understand their nature.

Contribution

It provides detailed spectral and morphological analysis of eight unidentified VHE gamma-ray sources from HESS, with no counterparts found, advancing understanding of these enigmatic sources.

Findings

No plausible multi-wavelength counterparts identified.

Spectral and morphological data for eight sources presented.

Results suggest these sources are a new class of gamma-ray emitters.

Abstract

The detection of gamma rays in the very-high-energy (VHE) energy range (100 GeV--100 TeV) provides a direct view of the parent population of ultra-relativistic particles found in astrophysical sources. For this reason, VHE gamma rays are useful for understanding the underlying astrophysical processes in non-thermal sources. We investigate unidentified VHE gamma-ray sources that have been discovered with HESS in the most sensitive blind survey of the Galactic plane at VHE energies conducted so far. The HESS array of imaging atmospheric Cherenkov telescopes (IACTs) has a high sensitivity compared with previous instruments(~ 0.01 Crab) in 25 hours observation time for a 5 sigma point-source detection), and with its large field of view, is well suited for scan-based observations. The on-going HESS survey of the inner Galaxy has revealed a large number of new VHE sources, and for each we attempt to associate the VHE emission with multi-wavelength data in the radio through X-ray wavebands. For each of the eight unidentified VHE sources considered here, we present the energy spectra and sky maps of the sources and their environment. The VHE morphology is compared with available multi-wavelength data (mainly radio and X-rays). No plausible counterparts are found.