Hubble Space Telescope Observations of GW170817: Complete Light Curves and the Properties of the Galaxy Merger of NGC 4993
Hubble Space Telescope Observations of GW170817: Complete Light Curves and the Properties of the Galaxy Merger of NGC 4993
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DOI：
10.3847/1538-4357/ac3e59
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发表时间：
2022-02
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通讯作者：
C. Kilpatrick;W. Fong;P. Blanchard;J. Leja;A. Nugent;A. Palmese;K. Paterson;T. Starkenburg;K. Alexander;E. Berger;R. Chornock;A. Hajela;R. Margutti
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作者：
C. Kilpatrick;W. Fong;P. Blanchard;J. Leja;A. Nugent;A. Palmese;K. Paterson;T. Starkenburg;K. Alexander;E. Berger;R. Chornock;A. Hajela;R. Margutti
我们展示了哈勃太空望远镜拍摄的中子星星合并双星GW 170817及其光学对应物AT 2017 gfo的完整图像。包括F814 W、F110 W、F140 W和F160 W在合并后3.4年的深度模板成像，我们重新分析了AT 2017 gfo在合并后5至1273个休息帧天的12个波段的全光变曲线。我们获得了短γ暴170817 A在并合后109 - 170个静止帧天的四个新的余辉观测结果。这些探测结果与先前观测到的β = −0.6的余辉光变曲线光谱指数一致，没有光谱演化的证据。我们还分析了我们的限制，在背景下的kilonova余辉或红外尘埃回波发射，但发现我们的限制是不约束这些模型。我们使用这些新数据来构建深度光学和红外堆栈，达到M = −6.3至−4.6等的极限，以分析AT 2017 gfo周围的局部环境及其宿主星系NGC 4993的低表面亮度特征。我们排除了在AT 2017 gfo到2.3 × 104 L <$的位置上存在任何球状星团的可能性，包括那些具有最红的V-H色的星团。最后，我们分析了NGC 4993在深残留成像中的子结构，发现NGC 4993的外壳特征延伸到71.″8（14.2 kpc）。壳层的累积恒星质量为6.3 × 108 M <$，约为NGC 4993的2%，质量加权年龄大于3 Gyr。我们的结论是，GW 170817的祖先系统不太可能在星系合并中形成。
We present the complete set of Hubble Space Telescope imaging of the binary neutron star merger GW170817 and its optical counterpart AT 2017gfo. Including deep template imaging in F814W, F110W, F140W, and F160W at 3.4 yr post-merger, we reanalyze the full light curve of AT 2017gfo across 12 bands from 5 to 1273 rest-frame days after merger. We obtain four new detections of the short γ-ray burst 170817A afterglow from 109 to 170 rest-frame days post-merger. These detections are consistent with the previously observed β = −0.6 spectral index in the afterglow light curve with no evidence for spectral evolution. We also analyze our limits in the context of kilonova afterglow or IR dust echo emission but find that our limits are not constraining for these models. We use the new data to construct deep optical and IR stacks, reaching limits of M = −6.3 to −4.6 mag, to analyze the local environment around AT 2017gfo and low surface brightness features in its host galaxy NGC 4993. We rule out the presence of any globular cluster at the position of AT 2017gfo to 2.3 × 104 L ⊙, including those with the reddest V − H colors. Finally, we analyze the substructure of NGC 4993 in deep residual imaging and find shell features that extend up to 71.″8 (14.2 kpc) from NGC 4993. The shells have a cumulative stellar mass of 6.3 × 108 M ⊙, roughly 2% of NGC 4993, and mass-weighted ages of >3 Gyr. We conclude that it was unlikely that the GW170817 progenitor system formed in the galaxy merger.