We use two-dimensional hydrodynamical simulations to investigate the properties of dense ejecta clumps (bullets) in a core-collapse supernova remnant, motivated by the observation of protrusions probably caused by clumps in the Vela supernova remnant. The ejecta, with an inner flat and an outer steep power-law density distribution, were assumed to freely expand into an ambient medium with a constant density, ~0.1 H atoms cm~(-3) for the case of Vela. At an age of 10~ 4 yr, the reverse shock front is expected to have moved back to the center of the remnant. Ejecta clumps with an initial density contrast χ ~100 relative to their surroundings are found to be rapidly fragmented and decelerated. In order to cause a pronounced protrusion on the blast wave, as observed in the Vela remnant, ~1000 may be required. In this case, the clump should be near the inflection point in the ejecta density profile, at an ejecta velocity ~3000 km s~(-1). These results apply to moderately large clumps; smaller clumps would require an even larger density contrast. Clumps can create ring structure in the shell of the Vela remnant, and we investigate the possibility that RX J0852-4622, an apparent supernova remnant superposed on Vela, is actually part of the Vela shell. Radio observations support this picture, but the possible presence of a compact object argues against it. The Ni bubble effect or compression in a pulsar wind nebula are possible mechanisms to produce the clumping.
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机译:我们使用二维流体动力学模拟来研究核心塌陷超新星残余物中稠密的喷射团块(子弹)的性质,这是由于观察到可能由Vela超新星残余物中的团块引起的突起而引起的。假定具有V形内表面和外部陡峭的幂律密度分布的喷射器可以自由膨胀到恒定密度的环境介质中,对于Vela而言,该密度为〜0.1 H原子cm〜(-3)。在10到4年的年龄中,预计反向冲击前沿将移回到残余部分的中心。相对于周围环境,初始密度差为χ〜100的弹射团块被迅速破碎和减速。为了在爆炸波上引起明显的突出,如在Vela残余中观察到的,可能需要〜1000。在这种情况下,团块应位于喷射密度分布图的拐点附近,喷射速度约为3000 km s〜(-1)。这些结果适用于中等大小的团块。较小的团块将需要更大的密度对比。团块可以在Vela残留物的外壳中形成环结构,我们研究了RX J0852-4622(一种明显的超新星残留物叠加在Vela上)实际上是Vela外壳的一部分的可能性。无线电观测支持此图,但可能存在的紧凑物体对此表示反对。镍气泡效应或脉冲星云中的压缩是产生团块的可能机制。
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