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arXiv · 1208.0113

Recombining Plasma and Hard X-ray Filament in the Mixed-Morphology Supernova Remnant W44

Hiroyuki Uchida·Katsuji Koyama·Hiroya Yamaguchi·Makoto Sawada·Takao Ohnishi·Takeshi Go Tsuru·Takaaki Tanaka·Satoshi Yoshiike·Yasuo Fukui
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Abstract

We report new features of the typical mixed-morphology (MM) supernova remnant (SNR) W44. In the X-ray spectra obtained with Suzaku, radiative recombination continua (RRCs) of highly ionized atoms are detected for the first time. The spectra are well reproduced by a thermal plasma in a recombining phase. The best-fit parameters suggest that the electron temperature of the shock-heated matters cooled down rapidly from $\sim1$,keV to $\sim 0.5$,keV, possibly due to adiabatic expansion (rarefaction) occurred $\sim20,000$ years ago. We also discover hard X-ray emission which shows an arc-like structure spatially-correlated with a radio continuum filament. The surface brightness distribution shows a clear anti-correlation with $^{12}$CO (J=2-1) emission from a molecular cloud observed with NANTEN2. While the hard X-ray is most likely due to a synchrotron enhancement in the vicinity of the cloud, no current model can quantitatively predict the observed flux.

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Hiroyuki Uchida, Katsuji Koyama, Hiroya Yamaguchi, Makoto Sawada, Takao Ohnishi, Takeshi Go Tsuru, Takaaki Tanaka, Satoshi Yoshiike, Yasuo Fukui. 2012-08-01. Recombining Plasma and Hard X-ray Filament in the Mixed-Morphology Supernova Remnant W44. https://doi.org/10.1093/pasj%2F64.6.141

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