Asymmetric expansion of the Fe ejecta in Kepler’s supernova remnant
Asymmetric expansion of the Fe ejecta in Kepler’s supernova remnant
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DOI：
10.1093/pasj/psy085
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发表时间：
2018-07
影响因子：
2.3
通讯作者：
T. Kasuga;Toshiki Sato;K. Mori;H. Yamaguchi;A. Bamba
中科院分区：
文献类型：
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作者：
T. Kasuga;Toshiki Sato;K. Mori;H. Yamaguchi;A. Bamba
超新星遗迹的抛射运动学是理解Ia型超新星爆炸机制的重要线索之一。特别是，铁峰元素的运动学不对称性为理解发生在爆发白矮星(WD)核心的物理过程提供了关键，尽管观测对其了解甚少。本文利用钱德拉记录数据，通过光谱分析和成像分析，首次揭示了开普勒信噪比中铁喷出物在视线方向的不对称膨胀结构。我们发现，Kα谱线的质心能量和谱线宽度相对较低($<；$6.4keV)和较窄($SIM$80 eV)，这意味着中心区域的大部分Fe喷射物是红移的。在外部区域，我们识别出明亮的蓝移结构，因为它可能是以高速致密团块的形式抛出的。考虑到铁电荷态的广泛布居，我们估计了每种速度结构的红移速度约为2,000公里/S，蓝移速度约为3,000公里/S。我们还提出了一种可能性，即中心附近的一部分铁喷出物与残骸近侧的致密星周介质(CSM)相互作用。作为铁喷出物不对称运动的起源，我们提出了三种情况：(1)CSM的不对称分布；(2)伴星在铁中投射的“阴影”；(3)不对称爆炸。
The ejecta kinematics of supernova remnants (SNRs) is one of crucial clues to understand the explosion mechanism of type Ia supernovae (SNe). In particular, the kinematic asymmetry of iron-peak elements provides the key to understanding physical processes taking place in the core of the exploding white dwarfs (WDs) although it has been poorly understood by observations. In this paper, we show for the first time the asymmetric expansion structure in the line-of-sight direction of Fe ejecta in Kepler's SNR revealed by spectral and imaging analysis using the Chandra archival data. We found that the K$\alpha$ line centroid energy and line width is relatively lower ($<$ 6.4 keV) and narrower ($\sim$80 eV) around the center of the remnant, which implies that the majority of the Fe ejecta in the central region is red-shifted. At the outer regions, we identify bright blue-shifted structures as it might have been ejected as high velocity dense clumps. Taking into account the broad population of the Fe charge states, we estimate the red-shifted velocity of ~2,000 km/s and the blue-shifted velocity of ~3,000 km/s for each velocity structure. We also present a possibility that a portion of the Fe ejecta near the center are interacting with the dense circumstellar medium (CSM) on the near side of the remnant. As the origin of the asymmetric motion of the Fe ejecta, we suggest three scenarios, (1) the asymmetric distribution of the CSM, (2) the "shadow" in Fe cast by the companion star, and (3) the asymmetric explosion.