论文标题
关于快速蓝色光学瞬变的性质
On the nature of Fast Blue Optical Transients
论文作者
论文摘要
快速蓝色光学瞬变（FBOT）的短上升时间需要非常轻的弹射信封，$ m_ {ej} \ leq 10^{ - 1} m_ \ odot $，比典型的超新星小得多。峰值时间短也意味着FBOT应该是流体动力的，而不是放射性的。 The detection by Chandra of X-ray emission in AT2020mrf of $L_X \sim 10^{42} $ erg s$^{-1}$ after 328 days implies total, overall dominant, X-ray energetics at the Gamma Ray Bursts (GRBs) level of $\sim 6 \times 10^{49}$ erg.我们进一步开发了Lyutikov＆Toonen（2019）的模型，该模型是FBOTS是后期吸积引起的崩溃（AIC）的结果，该产品是Onemg WD和另一个WD之间的Super-Chandrasekhar Double White Dwarf（WD）合并的乘积。小型喷射质量和FBOTS的稀有性是由从合并产品到风的质量损失与灰烬之间的竞争，并以$ \ sim 10^3-10^4 $年的时间尺度添加到核心中。 FBOT仅在AIC之前的信封质量为$ \ leq 10^{ - 1} m_ \ odot $时发生。适当的FBOTS来自中央发动机驱动的辐射主导的前向冲击，因为它通过射流传播。 Fbots的持续时间取决于NS驱动的向前冲击在扩展的喷射中产生的光子的扩散时间。中央源在射流内部深处产生的所有光子几乎同时逃脱，产生了一个简短的明亮事件。高能发射是在高度相对论和高度磁性终止冲击的情况下产生的，在质量上与脉冲星风云相似。 Lyutikov＆Toonen（2019）预测的SRG/Erosita在AT2020MRF中观察到的X射线颠簸来自于发动机驱动的冲击从射流到上一风。该模型只需几个$ \ times 10^{50} $ ergs，略高于观察到的X射线。我们预测该系统较差。
Short rise times of Fast Blue Optical Transients (FBOTs) require very light ejected envelopes, $M_{ej} \leq 10^{-1} M_\odot$, much smaller than of a typical supernova. Short peak times also mean that FBOTs should be hydrodynamically, not radioactively powered. The detection by Chandra of X-ray emission in AT2020mrf of $L_X \sim 10^{42} $ erg s$^{-1}$ after 328 days implies total, overall dominant, X-ray energetics at the Gamma Ray Bursts (GRBs) level of $\sim 6 \times 10^{49}$ erg. We further develop a model of Lyutikov & Toonen (2019), whereby FBOTs are the results of a late accretion induced collapse (AIC) of the product of super-Chandrasekhar double white dwarf (WD) merger between ONeMg WD and another WD. Small ejecta mass, and the rarity of FBOTs, result from the competition between mass loss from the merger product to the wind, and ashes added to the core, on time scale of $\sim 10^3-10^4$ years. FBOTs occur only when the envelope mass before AIC is $\leq 10^{-1} M_\odot$. FBOTs proper come from central engine-powered radiation-dominated forward shock as it propagates through ejecta. FBOTs' duration is determined by the diffusion time of photons produced by the NS-driven forward shock within the expanding ejecta. All the photons produced by the central source deep inside the ejecta escape almost simultaneously, producing a short bright event. The high energy emission is generated at the highly relativistic and highly magnetized termination shock, qualitatively similar to Pulsar Wind Nebulae. The X-ray bump observed in AT2020mrf by SRG/eROSITA, predicted by Lyutikov & Toonen (2019), is coming from the break-out of the engine-powered shock from the ejecta into the preceding wind. The model requires total energetics of just few $\times 10^{50}$ ergs, slightly above the observed X-rays. We predict that the system is hydrogen poor.
