Discovery of 6.4 keV line and soft X-ray emissions from G323.7$-$1.0 with Suzaku

Abstract

In this paper, the Suzaku X-ray data of the Galactic Supernova Remnant (SNR) candidate G323.7$-$1.0 are analyzed to search for X-ray emission. Spatially-extended enhancements in the 6.4 keV line and in soft X-rays are found inside or on the radio shell. The soft X-ray enhancement would be the hottest part of the shell-like X-ray emission along the radio shell. The 6.4 keV line enhancement is detected at a significance level of $4.1\sigma$. The lower limit of the equivalent width (EW) is 1.2 keV. The energy centroid of the 6.4 keV line is $6.40\pm 0.04$ keV, indicating that the iron is less ionized than the Ne-like state. If the 6.4 keV line originates from ionizing non-equilibrium thermal plasma, presence of iron-rich ejecta in a low-ionization state is required, which is disfavored by the relatively old age of the SNR. The 6.4 keV line enhancement would be due to K-shell ionization of iron atoms in a dense interstellar medium by high-energy particles. Since there is no irradiating X-ray source, the origin of the 6.4 keV line enhancement is not likely the photoionization. The large EW can only be explained by K-shell ionization due to cosmic-ray protons with an energy of $\sim 10$ MeV, which might be generated by the shock acceleration in G323.7$-$1.0.

13 pages, 6 figures, 2 tables, accepted by PASJ

References in corpus (6)

• Discriminating the Progenitor Type of Supernova Remnants with Iron K-Shell Emission
• Nonthermal X-rays from low-energy cosmic rays: Application to the 6.4 keV line emission from the Arches cluster region
• Scale heights and equivalent widths of the iron K-shell lines in the Galactic diffuse X-ray emission
• Discovery of Recombining Plasma in the Supernova Remnant 3C 391
• Suzaku spectra of a Type II Supernova Remnant Kes 79
• Detection of GeV Gamma-rays from HESS J1534-571 and Multiwavelength Implications for the Origin of the Non-thermal Emission

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• Probing Cosmic Rays with Fe K$\alpha$ Line Structures Generated by Multiple Ionization Process
• The Black Hole Candidate Swift J1728.9$-$3613 and the Supernova Remnant G351.9$-$0.9
• XMM-Newton observations of the TeV-discovered supernova remnant HESS J1534-571
• Suzaku Observations of Fe K-shell Lines in the Supernova Remnant W51C and Hard X-ray Sources in the Proximity