Continued Radio Observations of GW170817 3.5 yr Post-merger
Continued Radio Observations of GW170817 3.5 yr Post-merger
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DOI：
10.3847/2041-8213/abfd38
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发表时间：
2021-03
期刊：
影响因子：
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通讯作者：
A. Balasubramanian;A. Corsi;K. Mooley;M. Brightman;G. Hallinan;K. Hotokezaka;D. Kaplan;D. Lazzati;E. Murphy
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文献类型：
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作者：
A. Balasubramanian;A. Corsi;K. Mooley;M. Brightman;G. Hallinan;K. Hotokezaka;D. Kaplan;D. Lazzati;E. Murphy
我们介绍了双中子星合并GW170817与卡尔·G·詹斯基甚大阵列(VLA)在合并3年后进行的新的射电观测。我们的组合数据集是通过叠加超过≈32小时的VLA源时间得出的，因此提供了迄今为止在3 GHz处获得的GW170817场的最深组合观测(均方根灵敏度≈0.99μJy)。我们没有发现任何证据表明，在合并后1200d的平均历期t≈的射电重新变亮，而在同一平均历元，在X射线波长观测到的≈2.1σ超额。我们的测量结果与GW170817结构喷流的射电余辉峰后衰减的预期一致。利用这些结果，我们限制了模型的参数空间，这些模型预测可能由GW170817 konova抛射的高速尾巴引起的后期射电再亮，它将在合并数年后主导射电和X射线发射(一旦结构喷流余辉减弱到探测水平以下)。我们的结果表明，千诺瓦喷出物具有陡峭的能量-速度分布(能量-速度指数α≳为5)。我们提出了我们的射电分析的可能含义，结合最近关于X射线后期重新变亮的试探性证据，并强调有必要继续进行射电到X射线的监测，以测试不同的情况。
We present new radio observations of the binary neutron star merger GW170817 carried out with the Karl G. Jansky Very large Array (VLA) more than 3 yr after the merger. Our combined data set is derived by coadding more than ≈32 hr of VLA time on-source, and as such provides the deepest combined observation (rms sensitivity ≈0.99 μJy) of the GW170817 field obtained to date at 3 GHz. We find no evidence for a late-time radio rebrightening at a mean epoch of t ≈ 1200 days since merger, in contrast to a ≈2.1σ excess observed at X-ray wavelengths at the same mean epoch. Our measurements agree with expectations from the post-peak decay of the radio afterglow of the GW170817 structured jet. Using these results, we constrain the parameter space of models that predict a late-time radio rebrightening possibly arising from the high-velocity tail of the GW170817 kilonova ejecta, which would dominate the radio and X-ray emission years after the merger (once the structured jet afterglow fades below detection level). Our results point to a steep energy-speed distribution of the kilonova ejecta (with energy-velocity power-law index α ≳ 5). We suggest possible implications of our radio analysis, when combined with the recent tentative evidence for a late-time rebrightening in the X-rays, and highlight the need for continued radio-to-X-ray monitoring to test different scenarios.