On the Origin of TeV Gamma-Ray Emission from HESS J1834-087

Abstract

We present an X-ray study of the field containing the extended TeV source HESS J1834-087 using data obtained with the XMM-Newton telescope. Previously, the coincidence of this source with both the shell-type supernova remnant (SNR) W41 and a giant molecular cloud (GMC) was interpreted as favoring π⁰-decay γ-rays from interaction of the old SNR with the GMC. Alternatively, the TeV emission has been attributed to inverse Compton scattering from leptons deposited by PSR J1833-0827, a pulsar assumed to have been born in W41 but now located 24' from the center of the SNR (and the TeV source). Instead, we argue for a third possibility, that the TeV emission is powered by a previously unknown pulsar wind nebula located near the center of W41. The candidate pulsar is XMMU J183435.3-084443, a hard X-ray point source that lacks an optical counterpart to R > 21 and is coincident with diffuse X-ray emission. The X-rays from both the point source and diffuse feature are evidently nonthermal and highly absorbed. A best-fit power-law model yields photon index Γ ~ 0.2 and Γ ~ 1.9, for the point source and diffuse emission, respectively, and 2-10 keV flux ≈5 × 10^-13 erg cm^-2 s^-1 for each. At the measured 4 kpc distance of W41, the observed X-ray luminosity implies an energetic pulsar with \dot{E} ∼ 10^{36} d_4^2 erg s^-1, which is also sufficient to generate the observed γ-ray luminosity of 2.7 × 10³⁴ d ² ₄ erg s^-1 via inverse Compton scattering.