High-resolution X-ray study of supernova remnant J0453.6-6829 with unusually high forbidden-to-resonance ratio

Recent high-resolution X-ray spectroscopy has revealed that several supernova remnants (SNRs) in the Large Magellanic Cloud (LMC) show unusually high forbidden-to-resonance (f/r) line ratios. While their origin is still uncertain and debated, most of these SNRs have asymmetric morphology and/or show evidence of interaction with dense material, which may hint at the true nature of the anomalous f/r ratios. Here we report on a detailed spectral analysis of the LMC SNR J0453.6-6829 with the Reflection Grating Spectrometer (RGS) onboard XMM-Newton. We find that the f/r ratio of O VII (= 1.06(-0.10)(+0.09)) is significantly higher than expected from the previously reported thermal model. The spectrum is suitably explained by taking into account a charge exchange (CX) emission in addition to the thermal component. Analyzing archival ATCA and Parkes radio data, we also reveal that an H I cloud is possibly interacting with J0453.6-6829. These results support the presence of CX in J0453.6-6829, as the origin of the obtained high f/r ratio. Although a contribution of the resonance scattering (RS) cannot be ruled out at this time, we conclude that CX seems more likely than RS considering the relatively symmetric morphology of this remnant.