期刊
ASTROPHYSICAL JOURNAL
卷 871, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.3847/1538-4357/aaf8a6
关键词
ISM: abundances; ISM: individual objects (Cygnus Loop); ISM: supernova remnants; X-rays: ISM
资金
- JSPS KAKENHI [26800102, 16K17673, 17H02864, 16H03983]
- Leading Initiative for Excellent Young Researchers, MEXT, Japan
- Grants-in-Aid for Scientific Research [16K17673, 16H03983, 26800102] Funding Source: KAKEN
Charge exchange (CX) is an important process in shock physics because it indicates an interaction between downstream ions and ambient neutral hydrogen, suggesting the presence of a collisionless shock. We present a high-resolution spectroscopy of an X-ray bright spot in a nearby supernova remnant (SNR), the Cygnus Loop, with the Reflection Grating Spectrometer (RGS) on board XMM-Newton. The target is a compact knotty structure called the southwestern knot (SW-K) located at the outer edge of the shell, where the blast wave is likely interacting with dense surrounding materials. The RGS spectrum of the SW-K shows details of the line features below similar to 1 keV, where we discover a high forbidden-to-resonance line ratio of O VII He alpha. The soft-band (10-35 angstrom) spectrum is well explained by a thermal component with a CX X-ray emission obscured by neutral and ionized absorbers. The presence of the CX X-ray emission will provide new insights into the shock physics of SNRs. The high-resolution spectroscopy also reveals that the CNO, Ne, and Fe abundances are truly lower than the solar values (0.2-0.4 solar) at the SW-K region. Our result gives a clue to solving the previously known low-abundance problem reported from a number of evolved SNRs.
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