The Optical Afterglow of GW170817: An Off-axis Structured Jet and Deep Constraints on a Globular Cluster Origin
The Optical Afterglow of GW170817: An Off-axis Structured Jet and Deep Constraints on a Globular Cluster Origin
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DOI：
10.3847/2041-8213/ab3d9e
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发表时间：
2019-08
期刊：
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通讯作者：
W. Fong;P. Blanchard;P. Blanchard;K. Alexander;J. Strader;R. Margutti;A. Hajela;V. Villar;Y. Wu;Claire S. Ye;E. Berger;R. Chornock;D. Coppejans;P. Cowperthwaite;T. Eftekhari;D. Giannios;C. Guidorzi;A. Kathirgamaraju;A. Kathirgamaraju;T. Laskar;A. MacFadyen;B. Metzger;M. Nicholl;M. Nicholl;K. Paterson;G. Terreran;D. Sand;L. Sironi;P. G. Williams;P. G. Williams;Xiaoyi Xie;J. Zrake
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文献类型：
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作者：
W. Fong;P. Blanchard;P. Blanchard;K. Alexander;J. Strader;R. Margutti;A. Hajela;V. Villar;Y. Wu;Claire S. Ye;E. Berger;R. Chornock;D. Coppejans;P. Cowperthwaite;T. Eftekhari;D. Giannios;C. Guidorzi;A. Kathirgamaraju;A. Kathirgamaraju;T. Laskar;A. MacFadyen;B. Metzger;M. Nicholl;M. Nicholl;K. Paterson;G. Terreran;D. Sand;L. Sironi;P. G. Williams;P. G. Williams;Xiaoyi Xie;J. Zrake
我们给出了一个修正的和完整的双中子星合并GW170817的光学余辉曲线，这是由深度哈勃太空望远镜F606W在合并后584d的≈观测实现的，这提供了一个健壮的光学模板。该光曲线跨度为≈110362天，与之前由无线电和X射线数据显示的离轴观察的相对论结构喷流的辐射完全一致。结合同期的射电和X射线观测，我们没有发现光谱演化，其加权平均谱指数<β>=−0.583±0.013，表明在这些时间尺度上，射电和X射线波段之间没有同步加速器破裂频率的演化。我们发现GW170817的峰后时间斜率外推到宇宙学短伽马射线暴的亮度与观测到的喷流破裂时间相匹配，这表明它们的爆炸性质是相似的，GW170817的主要区别是视角。此外，我们对L≲6.7×10~3 L⊙或M≲1.3×10~4M⊙的球状星团(GC)的光度和质量进行了深刻的限制，这至少比宿主星系GC质量函数的峰值NGC4993低4个标准差。这一限制提供了GW170817没有在GC中形成和合并的直接和强烈的约束。正如这里强调的那样，HST(以及很快的詹姆斯·韦伯太空望远镜)能够对中子星合并喷流和流出的光学发射进行关键观测。
We present a revised and complete optical afterglow light curve of the binary neutron star merger GW170817, enabled by deep Hubble Space Telescope (HST) F606W observations at ≈584 days post-merger, which provide a robust optical template. The light curve spans ≈110–362 days, and is fully consistent with emission from a relativistic structured jet viewed off-axis, as previously indicated by radio and X-ray data. Combined with contemporaneous radio and X-ray observations, we find no spectral evolution, with a weighted average spectral index of 〈 β 〉 = − 0.583 ± 0.013 , demonstrating that no synchrotron break frequencies evolve between the radio and X-ray bands over these timescales. We find that an extrapolation of the post-peak temporal slope of GW170817 to the luminosities of cosmological short gamma-ray bursts matches their observed jet break times, suggesting that their explosion properties are similar, and that the primary difference in GW170817 is viewing angle. Additionally, we place a deep limit on the luminosity and mass of an underlying globular cluster (GC) of L ≲ 6.7 × 103 L⊙, or M ≲ 1.3 × 104 M⊙, at least 4 standard deviations below the peak of the GC mass function of the host galaxy, NGC 4993. This limit provides a direct and strong constraint that GW170817 did not form and merge in a GC. As highlighted here, HST (and soon the James Webb Space Telescope) enables critical observations of the optical emission from neutron star merger jets and outflows.