POSSIBLE CHARGE-EXCHANGE X-RAY EMISSION IN THE CYGNUS LOOP DETECTED WITH SUZAKU

被引:69
作者
Katsuda, Satoru [1 ]
Tsunemi, Hiroshi [2 ]
Mori, Koji [3 ]
Uchida, Hiroyuki [2 ]
Kosugi, Hiroko [2 ]
Kimura, Masashi [2 ]
Nakajima, Hiroshi [2 ]
Takakura, Satoru [2 ]
Petre, Robert [1 ]
Hewitt, John W. [1 ]
Yamaguchi, Hiroya [4 ]
机构
[1] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
[2] Osaka Univ, Grad Sch Sci, Dept Earth & Space Sci, Osaka 5600043, Japan
[3] Miyazaki Univ, Fac Engn, Dept Appl Phys, Miyazaki 8892192, Japan
[4] RIKEN, Inst Phys & Chem Res, Wako, Saitama 3510198, Japan
关键词
atomic processes; ISM: abundances; ISM: individual objects (Cygnus Loop); ISM: supernova remnants; X-rays: ISM; SUPERNOVA REMNANT 1E-0102.2-7219; XMM-NEWTON OBSERVATION; SOLAR-WIND; ABUNDANCE INHOMOGENEITY; NORTHEASTERN RIM; CHANDRA OBSERVATIONS; INTERSTELLAR-MEDIUM; PLASMA STRUCTURE; BACKGROUND MAPS; GALACTIC DISK;
D O I
10.1088/0004-637X/730/1/24
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
X-ray spectroscopic measurements of the Cygnus Loop supernova remnant indicate that metal abundances throughout most of the remnant's rim are depleted to similar 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 similar 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 similar to 0.7 keV. This feature is likely a complex of He-like O K(gamma + delta + epsilon), although other possibilities cannot be fully excluded. The intensity of this emission relative to He-like O K alpha 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.
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页数:15
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