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تسجيل مستخدم جديدTemporal and Spatial Variation of Synchrotron X-ray Stripes in Tychos Supernova Remnant
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The synchrotron X-ray stripes discovered in Tychos supernova remnant (SNR) have been attracting attention since they may be evidence for proton acceleration up to PeV. We analyzed Chandra data taken in 2003, 2007, 2009, and 2015 for imaging and spectroscopy of the stripes in the southwestern region of the SNR. Comparing images obtained at different epochs, we find that time variability of synchrotron X-rays is not limited to two structures previously reported but is more common in the region. Spectral analysis of nine bright stripes reveals not only their time variabilities but also a strong anti-correlation between the surface brightness and photon indices. The spectra of the nine stripes have photon indices of Gamma = 2.1--2.6 and are significantly harder than those of the outer rim of the SNR in the same region with Gamma = 2.7--2.9. Based on these findings, we indicate that the magnetic field is substantially amplified, and suggest that particle acceleration through a stochastic process may be at work in the stripes.
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Analyzing Chandra data of Tychos supernova remnant (SNR) taken in 2000, 2003, 2007, 2009, and 2015, we search for time variable features of synchrotron X-rays in the southwestern part of the SNR, where stripe structures of hard X-ray emission were pr
evious found. By comparing X-ray images obtained at each epoch, we discover a knot-like structure in the northernmost part of the stripe region became brighter particularly in 2015. We also find a bright filamentary structure gradually became fainter and narrower as it moved outward. Our spectral analysis reveal that not only the nonthermal X-ray flux but also the photon indices of the knot-like structure change from year to year. During the period from 2000 to 2015, the small knot shows brightening of $sim 70%$ and hardening of $Delta Gamma sim 0.45$. The time variability can be explained if the magnetic field is amplified to $sim 100~mathrm{mu G}$ and/or if magnetic turbulence significantly changes with time.
High-resolution Chandra observations of Tychos SNR have revealed several sets of quasi-steady, high-emissivity, nearly-parallel X-ray stripes in some localized regions of the SNR. These stripes are most likely the result of cosmic-ray (CR) generated
magnetic turbulence at the SNR blast wave. However, for the amazingly regular pattern of these stripes to appear requires the simultaneous action of a number of shock-plasma phenomena and is not predicted by most models of magnetic field amplification. A consistent explanation of these stripes yields information on the complex nonlinear plasma processes connecting efficient CR acceleration and magnetic field fluctuations in strong collisionless shocks. The nonlinear diffusive shock acceleration (NL-DSA) model described here, which includes magnetic field amplification from a cosmic-ray current driven instability, does predict stripes consistent with the synchrotron emission observations of Tychos SNR. We argue that the local ambient mean magnetic field geometry determines the orientation of the stripes and therefore it can be reconstructed with the high resolution X-ray imaging. The estimated maximum energy of the CR protons responsible for the stripes is $sim 10^{15}$,eV. Furthermore, the model predicts that a specific X-ray polarization pattern, with a polarized fraction ~ 50%, accompanies the stripes, which can be tested with future X-ray polarimeter missions.
We present X-ray proper-motion measurements of the forward shock and reverse-shocked ejecta in Tychos supernova remnant, based on three sets of archival Chandra data taken in 2000, 2003, and 2007. We find that the proper motion of the edge of the rem
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Recent rapid development of deep learning algorithms, which can implicitly capture structures in high-dimensional data, opens a new chapter in astronomical data analysis. We report here a new implementation of deep learning techniques for X-ray analy
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