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arXiv 1702.06555astro-ph.HE
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最年轻的银河系超新星遗迹G1 .9+0.3的非对称膨胀

Asymmetric Expansion of the Youngest Galactic Supernova Remnant G1.9+0.3

K. J. Borkowski, P. Gwynne, S. P. Reynolds, D. A. Green, U. Hwang, R. Petre, R. Willett

摘要:

最年轻的银河系超新星遗迹(SNR)G1.9+0.3,是由(可能的)Ia型超新星在$\sim 1900$ CE爆炸后产生的,在射电波长上是强烈不对称的,在北面要亮得多,但在X射线上是两侧对称的。我们提出了X射线膨胀测量的结果,阐明了射电不对称性的起源。我们确认平均扩张率(2011年至2015年)为每年0.58%,但存在较大的空间差异。使用非参数“Demons”方法,我们测量了整个SNR的速度场,发现运动变化了5倍,从每年0.09”到0.44”。最慢的震波位于明亮的北部射电边缘的外边界,速度$v_s$低至3,600 km/s(假设距离为8.5 kpc),远低于沿X射线明亮主轴的$v_s = 12,000 - 13,000$ km/s。北部冲击波如此强烈的减速很可能是由于SN喷出物与那里比平均环境介质密度大得多的介质碰撞造成的。这种不对称的环境介质自然地解释了无线电不对称性。在几个位置,显着的形态变化和强烈的非径向运动是明显的。空间积分的X射线通量继续随时间增加。根据Chandra长达8.3年的观测,我们测量出其每年增长1.3% +/- 0.8%。SN喷出物很可能与SN祖先在爆炸前喷出的不对称拱星介质碰撞。

英文摘要:

The youngest Galactic supernova remnant (SNR) G1.9+0.3, produced by a (probable) SN Ia that exploded $\sim 1900$ CE, is strongly asymmetric at radio wavelengths, much brighter in the north, but bilaterally symmetric in X-rays. We present the results of X-ray expansion measurements that illuminate the origin of the radio asymmetry. We confirm the mean expansion rate (2011 to 2015) of 0.58% per year, but large spatial variations are present. Using the nonparametric "Demons" method, we measure the velocity field throughout the entire SNR, finding that motions vary by a factor of 5, from 0.09" to 0.44" per year. The slowest shocks are at the outer boundary of the bright northern radio rim, with velocities $v_s$ as low as 3,600 km/s (for an assumed distance of 8.5 kpc), much less than $v_s = 12,000 - 13,000$ km/s along the X-ray-bright major axis. Such strong deceleration of the northern blast wave most likely arises from the collision of SN ejecta with a much denser than average ambient medium there. This asymmetric ambient medium naturally explains the radio asymmetry. In several locations, significant morphological changes and strongly nonradial motions are apparent. The spatially-integrated X-ray flux continues to increase with time. Based on Chandra observations spanning 8.3 years, we measure its increase at 1.3% +/- 0.8% per year. The SN ejecta are likely colliding with the asymmetric circumstellar medium ejected by the SN progenitor prior to its explosion.

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