XMM-Newton observations of the TeV-discovered supernova remnant HESS J1534-571

TL;DR

XMM-Newton observations of the supernova remnant HESS J1534-571 reveal no X-ray synchrotron emission but detect a 6.4 keV line, suggesting cosmic-ray interactions with dense gas, informing the origin of its gamma-ray emission.

Contribution

This study provides the first XMM-Newton analysis of HESS J1534-571, setting upper limits on X-ray flux and identifying a 6.4 keV line, advancing understanding of cosmic-ray interactions in this SNR.

Findings

No X-ray synchrotron emission detected.

Detected 6.4 keV line emission in localized regions.

Upper limit on X-ray flux in 2-10 keV band.

Abstract

We report the results obtained from XMM-Newton observations of the TeV-detected supernova remnant (SNR) HESS J1534-571. We focus on the nature of the cosmic-ray particle content in the SNR, which is revealed by its $\gamma$-ray emission. No signatures of X-ray synchrotron emission were detected from the SNR. This is consistent with earlier results obtained with Suzaku from other regions of the object. A joint modeling of the XMM-Newton and Suzaku spectra yields an upper limit for the total X-ray flux from the SNR area of $\sim$ 5.62$ \times 10^{-13} \ \mathrm{erg\ cm^{-2}\ s^{-1}}$ (95% c.l.) in the energy band of 2-10 keV, for an assumed photon index of 2.0. On the other hand, we do find evidence in the XMM-Newton data for a line-like emission feature at 6.4 keV from localized regions, again confirming earlier Suzaku measurements. We discuss the findings in the context of the origin of the observed $\gamma$-ray emission. Although neither hadronic nor leptonic scenarios can be fully ruled out, the observed line emission can be interpreted as the result of interactions between lower energy ($\sim$ MeV) cosmic-ray protons with high gas density regions in and around HESS J1534-571, and thus potentially be associated with particles accelerated in the SNR.