用光回波直接证实Cas A超新星的不对称性
Direct Confirmation of the Asymmetry of the Cas A Supernova with Light Echoes
摘要：
我们报告的第一个检测的不对称性的超新星（SN）光球的基础上SN光回波（LE）光谱的Cas A从不同的角度尘埃浓度的LE椭球。基于差分图像，报道了新的发光二极管，并对这些发光二极管的光谱进行了分析和比较。在适当考虑有限的尘埃细丝的范围和倾斜的影响后，我们发现一个领域的He I和H α功能蓝移了额外的~4000 km/s相对于其他光谱和IIb型SN 1993 J的光谱。相同的方向不显示任何位移相对于其他Cas A LE光谱中的Ca II近红外三重态功能。我们比较的角度与最近的三维建模的SN残余（SNR）的Cas A LE尘埃浓度，并注意到，具有蓝移的He I和H α功能的位置大致是在一个富铁流出的方向和在相反的方向上的紧凑的对象的运动在SNR的中心。我们得出结论，Cas A是一个本质上不对称的SN。未来的LE光谱的这个对象，和其他历史的SNe，将提供更多的洞察爆炸机制的连接到SN到SNR，以及提供关键的观测证据，恒星如何爆炸。
英文摘要：
We report the first detection of asymmetry in a supernova (SN) photosphere based on SN light echo (LE) spectra of Cas A from the different perspectives of dust concentrations on its LE ellipsoid. New LEs are reported based on difference images, and optical spectra of these LEs are analyzed and compared. After properly accounting for the effects of finite dust-filament extent and inclination, we find one field where the He I and H alpha features are blueshifted by an additional ~4000 km/s relative to other spectra and to the spectra of the Type IIb SN 1993J. That same direction does not show any shift relative to other Cas A LE spectra in the Ca II near-infrared triplet feature. We compare the perspectives of the Cas A LE dust concentrations with recent three-dimensional modeling of the SN remnant (SNR) and note that the location having the blueshifted He I and H alpha features is roughly in the direction of an Fe-rich outflow and in the opposite direction of the motion of the compact object at the center of the SNR. We conclude that Cas A was an intrinsically asymmetric SN. Future LE spectroscopy of this object, and of other historical SNe, will provide additional insight into the connection of explosion mechanism to SN to SNR, as well as give crucial observational evidence regarding how stars explode.
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