The First Second of a Type II Supernova: Convection, Accretion, and Shock Propagation
The First Second of a Type II Supernova: Convection, Accretion, and Shock Propagation
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II 型超新星的第一秒：对流、吸积和冲击传播
DOI：
10.1086/309604
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
E. Mueller
中科院分区：
文献类型：
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作者：
H. Janka;E. Mueller
对 15 M☉ 恒星中微子驱动的超新星爆炸的一维和二维流体动力学模拟，针对瞬发激波停滞和核心弹跳后 1 s 之间的阶段进行。来自 ν 球体的中微子 (ν) 通量的变化表明，爆炸能量和时间尺度、初始原中子星质量和 Fe 族元素的爆炸核合成敏感地依赖于激波形成后最初几百毫秒内 ν 加热的强度。激波后面 ν 加热区域的对流翻转对于仅在 ν 光度狭窄窗口内的爆炸至关重要。这里只有在多维情况下才能获得强大的爆炸，主要是因为翻转通过允许冷的震后物质向内渗透到最强加热区域来提高ν能量沉积的效率，而加热的气体可以快速向外上升，从而减少由于中微子重新发射而造成的能量损失。一维和二维模型中爆炸能量随时间的不同增加支持了这种解释。对于较高的核心 ν 通量，球对称模型也会产生高能爆炸，而对于较低的光度，即使有对流，也不会发生强烈的爆炸。从激波到加热区的下流中的冷气体通过 νe 发射失去轻子，但通过与核心 ν 通量的相互作用获得能量。然而，由于它的氮含量不是非常丰富并且其熵增加，因此它不会吸积到中子星的低熵中子化表面中。由于爆炸在 100 毫秒的时间尺度上发展时没有显着的吸积，因此最初的原中子星（重子）质量仅为约 1.2 M☉。中子星周围的湍流活动是短暂的；在激波形成后 200-300 毫秒，湍流层与 ν 加热区解耦，并在超新星激波后面向外移动。冲击显示出大范围的变形。温度 T、密度 ρ 和速度的不均匀性与激波后壳中 30°-45° 尺度上的有序统一性对比有助于解释 SN 1987A 中观察到的各向异性和径向混合。当超新星激波在反弹后约 400-500 毫秒到达 5700 km 处的 Si-O 界面熵阶时，中子星周围致密壳层和低密度“热气泡”区域之间的 ρ 反转开始陡峭成强烈的反向激波，从而在来自新生中子星的 ν 驱动风中形成急剧的不连续性。风膨胀的减速可能会在几秒的时间尺度内引发物质向中子星的显着的各向异性回落。
One- and two-dimensional hydrodynamical simulations of the neutrino-driven supernova explosion of a 15 M☉ star are performed for the phase between stagnation of the prompt shock and 1 s after core bounce. Variation of the neutrino (ν) fluxes from the ν sphere shows that explosion energy and timescale, initial proto-neutron star mass, and explosive nucleosynthesis of Fe group elements depend sensitively on the strength of the ν heating during the first few 100 ms after shock formation. Convective overturn in the ν-heated region behind the shock is a crucial help for the explosion only in a narrow window of ν luminosities. Here powerful explosions can be obtained only in the multidimensional case, primarily because the overturn increases the efficiency of ν energy deposition by allowing cool postshock matter to penetrate inward to the region of strongest heating, while heated gas can quickly rise outward, thus reducing its energy loss due to reemission of neutrinos. This interpretation is supported by the different increase of the explosion energy with time in one- and two-dimensional models. For higher core ν fluxes spherically symmetrical models also yield energetic explosions, while for lower luminosities even with convection, no strong explosions occur. Cool gas in downflows from the shock to the heating zone loses leptons by νe emission but gains energy by interactions with the core ν fluxes. However, because it does not get very n rich and its entropy increases, it is not accreted into the low-entropy, neutronized surface of the neutron star. Because of the absence of significant accretion while the explosions develop on a timescale of a few 100 ms, the initial proto-neutron star (baryonic) masses are only ~1.2 M☉. Turbulent activity around the neutron star is transient; at 200-300 ms after shock formation, the turbulent layer decouples from the ν-heated zone and moves outward behind the supernova shock. The shock shows deformation on large scales. Inhomogeneities of temperature T, density ρ, and velocity with contrasts of order unity on scales of 30°-45° in the shell behind the shock could help to explain anisotropies and radial mixing observed in SN 1987A. When the supernova shock reaches the entropy step of the Si-O interface at 5700 km about 400-500 ms after bounce, the ρ inversion between the dense shell and the low-density, “hot bubble” region around the neutron star begins to steepen into a strong reverse shock that forms a sharp discontinuity in the ν-driven wind from the nascent neutron star. The deceleration of the wind expansion might trigger significant, anisotropic fallback of matter to the neutron star on a timescale of several seconds.
Masayuki Inoue：“牙周病和冠桥修复体的初始或加速因素”J J S P. 5. 2-10 (1987)
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