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arXiv · 1402.0603

X-ray Spectroscopy of the Mixed Morphology Supernova Remnant W28 with XMM-Newton

Ryoko Nakamura·Aya Bamba·Manabu Ishida·Ryo Yamazaki·Ken'ichi Tatematsu·Kazunori Kohri·Gerd P\" uhlhofer{7}·Stefan J. Wagner{8}·Makoto Sawada{2}
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Abstract

We report on spatially resolved X-ray spectroscopy of the north-eastern part of the mixed morphology supernova remnant (SNR) W28 with {\it XMM-Newton}. The observed field of view includes a prominent and twisted shell emission forming the edge of this SNR as well as part of the center-filled X-ray emission brightening toward the south-west edge of the field of view. The shell region spectra are in general represented by an optically thin thermal plasma emission in collisional ionization equilibrium with a temperature of $\sim$0.3~keV and a density of $\sim$10~cm$^{-3}$, which is much higher than the density obtained for inner parts. In contrast, we detected no significant X-ray flux from one of the TeV $γ$-ray peaks with an upper-limit flux of 2.1$\times$10$^{-14}$ erg cm$^{-2}$ s$^{-1}$ in the 2--10~keV band. The large flux ratio of TeV to X-ray, larger than 16, and the spatial coincidence of the molecular cloud and the TeV $γ$-ray emission site indicate that the TeV $γ$-ray of W28 is $π^{0}$-decay emission originating from collisions between accelerated protons and molecular cloud protons. Comparing the spectrum in the TeV band and the X-ray upper limit, we obtained a weak upper limit on the magnetic field strength $B\lesssim$ 1500~$μ$G.

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Ryoko Nakamura, Aya Bamba, Manabu Ishida, Ryo Yamazaki, Ken'ichi Tatematsu, Kazunori Kohri, Gerd P\" uhlhofer{7}, Stefan J. Wagner{8}, Makoto Sawada{2}. 2014-02-04. X-ray Spectroscopy of the Mixed Morphology Supernova Remnant W28 with XMM-Newton. https://doi.org/10.1093/pasj%2Fpsu031

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