XMM-牛顿RGS揭示的富氧超新星残余船尾座A中X射线发射物的动力学
Dynamics of X-Ray-Emitting Ejecta in the Oxygen-Rich Supernova Remnant Puppis A Revealed by the XMM-Newton RGS
摘要：
利用XMM-牛顿号上反射光栅光谱仪（RGS）前所未有的光谱分辨率，我们揭示了富氧超新星遗迹船尾座A中发射X射线的喷出物的动力学。RGS光谱显示出突出的K壳层线，包括O VII He_alpha禁戒和共振，O VIII Ly_alpha，O VIII Ly_beta和Ne IX He_alpha共振，这些线来自与光学富氧细丝（遗迹东北部所谓的Omega细丝）位置一致的喷出物结。我们发现，线的质心蓝移了1480+/-140+/-60 km/s（第一和第二项误差分别是测量和校准不确定性），这是完全一致的光学欧米茄灯丝。在654 eV（对应于O VIII Ly_alpha）处获得的谱线展宽小于~0.9 eV，表明氧温度小于~30 keV。对XMM-牛顿MOS谱的分析表明，电子温度约为0.8 keV，电离时标约为2 e10 cm^-3 s。我们表明，氧和电子的温度以及电离时标可以调和，如果喷出物结被加热的碰撞冲击，其速度是~600-1200公里/秒，随后由于库仑相互作用平衡。RGS光谱还显示了位于残骸东北边缘附近的另一个喷出物特征的相对较弱的K壳层线，从中我们测量到650+/-70+/-60 km/s的向红多普勒速度。
英文摘要：
Using the unprecedented spectral resolution of the reflection grating spectrometer (RGS) onboard XMM-Newton, we reveal dynamics of X-ray--emitting ejecta in the oxygen-rich supernova remnant Puppis A. The RGS spectrum shows prominent K-shell lines, including O VII He_alpha forbidden and resonance, O VIII Ly_alpha, O VIII Ly_beta, and Ne IX He_alpha resonance, from an ejecta knot positionally coincident with an optical oxygen-rich filament (the so-called Omega filament in the northeast of the remnant). We find that the line centroids are blueshifted by 1480+/-140+/-60 km/s (the first and second term errors are measurement and calibration uncertainties, respectively), which is fully consistent with that of the optical Omega filament. Line broadening at 654 eV (corresponding to O VIII Ly_alpha) is obtained to be less than ~0.9 eV, indicating an oxygen temperature of less than ~30 keV. Analysis of XMM-Newton MOS spectra shows an electron temperature of ~0.8 keV and an ionization timescale of ~2e10 cm^-3 s. We show that the oxygen and electron temperatures as well as the ionization timescale can be reconciled if the ejecta knot was heated by a collisionless shock whose velocity is ~600-1200 km/s and was subsequently equilibrated due to Coulomb interactions. The RGS spectrum also shows relatively weak K-shell lines of another ejecta feature located near the northeastern edge of the remnant, from which we measure redward Doppler velocities of 650+/-70+/-60 km/s.
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