The cocoon emission - an electromagnetic counterpart to gravitational waves from neutron star mergers
The cocoon emission - an electromagnetic counterpart to gravitational waves from neutron star mergers
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DOI：
10.1093/mnras/stx2357
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发表时间：
2018-01-01
影响因子：
4.8
通讯作者：
Piran, Tsvi
中科院分区：
文献类型：
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作者：
Gottlieb, Ore;Nakar, Ehud;Piran, Tsvi
短伽马射线暴被认为是由紧密的双星合并（中子星-中子星星或黑洞-中子星星）产生的。如果是这样的话，它们的喷流必须穿透在合并过程中喷出的外流。当射流穿过喷出物时，它会耗散能量，产生一个热茧包围着它。我们在这里对合并流出物中的射流传播进行了3D数值模拟，并计算了由此产生的排放。这种辐射由两部分组成：冷却辐射，热茧的热能泄漏，以及茧材料的放射性衰变产生的茧macronova。这种发射给出了一个简短的（类似于1小时）蓝色，广角信号。虽然外流和喷流的参数是不确定的，但对于我们所考虑的配置，信号是明亮的（类似于-14到-15的绝对星等），并且胜过所有其他预测的紫外光信号。当喷流爆发时间较长时，信号较亮，并且其峰值亮度并不强烈地依赖于高度不确定的不透明度。快速搜索这样的信号是探测电磁合并对应物的一种有前途的策略。然后，可以对检测到的候选物质进行深红外搜索，以寻找从其余喷出物中产生的较长但较弱的macronova。
Short gamma-ray bursts are believed to arise from compact binary mergers (either neutron star-neutron star or black hole-neutron star). If so, their jets must penetrate outflows that are ejected during the merger. As a jet crosses the ejecta, it dissipates its energy, producing a hot cocoon that surrounds it. We present here 3D numerical simulations of jet propagation in mergers' outflows, and we calculate the resulting emission. This emission consists of two components: the cooling emission, the leakage of the thermal energy of the hot cocoon, and the cocoon macronova that arises from the radioactive decay of the cocoon's material. This emission gives a brief (similar to 1 h) blue, wide angle signal. While the parameters of the outflow and jet are uncertain, for the configurations we have considered, the signal is bright (similar to-14 to -15 absolute magnitude) and outshines all other predicted ultraviolet-optical signals. The signal is brighter when the jet breakout time is longer, and its peak brightness does not depend strongly on the highly uncertain opacity. A rapid search for such a signal is a promising strategy to detect an electromagnetic merger counterpart. A detected candidate could be then followed by deep infrared searches for the longer but weaker macronova arising from the rest of the ejecta.