Constraining leptonic emission scenarios for the PeVatron candidate HESS J1702-420 with deep XMM-Newton observations

TL;DR

This study uses deep XMM-Newton X-ray observations to investigate the leptonic emission scenarios of the PeVatron candidate HESS J1702-420, setting upper limits on X-ray emission and exploring possible associations with new sources.

Contribution

It provides the first deep X-ray constraints on HESS J1702-420A, introduces a multi-wavelength modeling toolkit, and reports a new extended X-ray source near the PeVatron candidate.

Findings

No clear X-ray counterpart was detected for HESS J1702-420A.

Strict upper limits on diffuse X-ray emission and magnetic field were established.

A new extended X-ray source was serendipitously discovered.

Abstract

The unidentified TeV source HESS J1702-420 has recently been proposed as a new hadronic PeVatron candidate, based on the discovery of a small-scale emission sub-region with extremely hard gamma-ray spectrum up to 100 TeV (named HESS J1702-420A). Given the difficulty to discriminate between a hadronic or leptonic origin of the TeV emission, based on the H.E.S.S. measurement alone, we opted for a multi-wavelength approach. A deep X-ray observation was carried out using the XMM-Newton satellite, with the goal of probing a possible association with a hidden leptonic accelerator. No evidence of a clear counterpart for HESS J1702-420A was found in the X-ray data. After excluding an association with all nearby X-ray point sources, we derived strict upper limits on the diffuse X-ray emission and average magnetic field in the HESS J1702-420A region. We additionally report the serendipitous discovery of a new extended X-ray source, whose association with HESS J1702-420A is not obvious but cannot be ruled out either. A set of scripts dedicated to the multi-wavelength modeling of X-ray and gamma-ray data, based on Gammapy, Naima and Xspec, was developed in the context of this work and is made publicly available along with this paper.