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Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE
Abstract:
Previous observations with HESS have revealed the existence of an extended
very-high-energy (VHE; E>100 GeV) gamma-ray source, HESS J1834-087, coincident
with the SNR W41. The origin of the gamma-ray emission has been further
investigated with HESS and the Fermi-LAT. The gamma-ray data provided by 61h
(HESS) and 4 yrs (Fermi LAT) of observations cover over 5 decades in energy
(1.8GeV - 30TeV). The morphology and spectrum of the TeV and GeV sources have
been studied and multi-wavelength data have been used to investigate the origin
of the observed emission. The TeV source can be modeled with a sum of two
components: one point-like and one significantly extended (sig_TeV =
0.17{\deg}), both centered on SNR W41 and exhibiting spectra described by a
power law of index 2.6. The GeV source detected with Fermi is extended (sig_GeV
=0.15{\deg}) and morphologically matches the VHE emission. Its spectrum can be
described by a power-law with index 2.15 and joins smoothly the one of the
whole TeV source. A break appears in the spectra around 100 GeV. Two main
scenarios are proposed to explain the emission: a pulsar wind nebula (PWN) or
the interaction of SNR W41 with a molecular cloud. X-ray observations suggest
the presence of a point-like source (pulsar candidate) near the center of the
SNR and non-thermal X-ray diffuse emission which could arise from a potential
PWN. The PWN scenario is supported by the match of of the TeV and GeV positions
with the putative pulsar. However, the overall spectrum is reproduced by a
1-zone leptonic model only if an excess of low-energy electrons is injected by
a high spin-down power pulsar. This low-energy component is not needed if the
point-like TeV source is unrelated to the extended GeV and TeV sources. The
interacting SNR scenario is supported by the spatial coincidence between the
gamma-ray sources, the detection of OH maser lines and the hadronic modeling.
