Shocked jets in CCSNe can power the zoo of fast blue optical transients
Shocked jets in CCSNe can power the zoo of fast blue optical transients
复制标题
CCSNe 中的冲击射流可为快速蓝色光学瞬变动物园提供动力
DOI：
10.1093/mnras/stac910
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发表时间：
2022
影响因子：
4.8
通讯作者：
Margutti, Raffaella
中科院分区：
文献类型：
--
作者：
Gottlieb, Ore;Tchekhovskoy, Alexander;Margutti, Raffaella
越来越多的证据表明，最近对恒星形成星系中快速蓝色光学瞬变（FBOT）的多波长探测包括一类新的瞬变，其起源尚待了解。我们证明，在中央发动机附近发射相对论性喷流的富氢塌缩恒星可以自然地解释整套 FBOT 可观测数据。射流-恒星相互作用形成了一个温和相对论性的冲击射流（内茧）成分，它为冷却发射提供动力，在最初几周内主导高速光信号，典型能量为~1050-1051erg。在此期间，茧径向能量分布意味着光学光曲线呈现快速衰减。几周后，当发射壳的速度约为 0.01 c 时，茧变得透明，冷却外壳控制发射。茧与稠密的星周风之间的相互作用产生射电波段的同步加速器自吸收发射，其特征是在一个月的时间尺度上稳定上升。几个月后，相对论流出减速，进入观察者的视线，并为射电光曲线的峰值提供动力，此后迅速衰减。塌陷后的第二天，喷流（以及内部茧）对于 X 射线来说变得光学变薄，从而使 X 射线光子从将喷流发射到观察者的中央发动机中扩散出来。与 FBOT 类似，茧冷却发射的体积速率预计比伽马射线暴 (GRB) 高几倍。我们排除了非准直流出，但是，GRB 喷流和失败的准直喷流都与所有可观测值兼容。
Evidence is mounting that recent multiwavelength detections of fast blue optical transients (FBOTs) in star-forming galaxies comprise a new class of transients, whose origin is yet to be understood. We show that hydrogen-rich collapsing stars that launch relativistic jets near the central engine can naturally explain the entire set of FBOT observables. The jet–star interaction forms a mildly relativistic shocked jet (inner cocoon) component, which powers cooling emission that dominates the high velocity optical signal during the first few weeks, with a typical energy of ∼1050–1051erg. During this time, the cocoon radial energy distribution implies that the optical light curve exhibits a fast decay of. After a few weeks, when the velocity of the emitting shell is ∼0.01 c, the cocoon becomes transparent, and the cooling envelope governs the emission. The interaction between the cocoon and the dense circumstellar winds generates synchrotron self-absorbed emission in the radio bands, featuring a steady rise on a month time-scale. After a few months the relativistic outflow decelerates, enters the observer’s line of sight, and powers the peak of the radio light curve, which rapidly decays thereafter. The jet (and the inner cocoon) becomes optically thin to X-rays ∼day after the collapse, allowing X-ray photons to diffuse from the central engine that launched the jet to the observer. Cocoon cooling emission is expected at higher volumetric rates than gamma-ray bursts (GRBs) by a factor of a few, similar to FBOTs. We rule out uncollimated outflows, however, both GRB jets and failed collimated jets are compatible with all observables.