2011/02/28 by Satoru Katsuda, H. Tsunemi, Hiroshi Tsunemi +10
Physics and Astronomy · #Abundance (ecology) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Charge exchange #Emission spectrum #Gamma-ray bursts and supernovae #Ion #Physics #Spectral line #Supernova #Thermal #astro-ph.HE
paper · pdf · doi:10.1088/0004-637x/730/1/24
published as ApJ, 730, 24 (2011) · Published in ApJ
openalex publication_date 2011/02/28 · arxiv created 2011/03/09 · arxiv updated 2015/05/27 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
X-ray spectroscopic measurements of the Cygnus Loop supernova remnant indicate that metal abundances throughout most of the remnant's rim are depleted to ∼0.2 times the solar value. However, recent X-ray studies have revealed in some narrow regions along the outermost rim anomalously "enhanced" abundances (up to ∼1 solar). The reason for these anomalous abundances is not understood. Here, we examine X-ray spectra in annular sectors covering nearly the entire rim of the Cygnus Loop using Suzaku (21 pointings) and XMM-Newton (1 pointing). We find that spectra in the "enhanced" abundance regions commonly show a strong emission feature at ∼0.7 keV. This feature is likely a complex of He-like O K(γ + δ + ), although other possibilities cannot be fully excluded. The intensity of this emission relative to He-like O Kα appears to be too high to be explained as thermal emission. This fact, as well as the spatial concentration of the anomalous abundances in the outermost rim, leads us to propose an origin from charge-exchange processes between neutrals and H-like O. We show that the presence of charge-exchange emission could lead to the inference of apparently "enhanced" metal abundances using pure thermal emission models. Accounting for charge-exchange emission, the actual abundances could be uniformly low throughout the rim. The overall abundance depletion remains an open question.