RADIO MONITORING OF THE TIDAL DISRUPTION EVENT SWIFT J164449.3+573451. II. THE RELATIVISTIC JET SHUTS OFF AND A TRANSITION TO FORWARD SHOCK X-RAY/RADIO EMISSION
RADIO MONITORING OF THE TIDAL DISRUPTION EVENT SWIFT J164449.3+573451. II. THE RELATIVISTIC JET SHUTS OFF AND A TRANSITION TO FORWARD SHOCK X-RAY/RADIO EMISSION
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DOI：
10.1088/0004-637x/767/2/152
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发表时间：
2012-12
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影响因子：
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通讯作者：
B. Zauderer;E. Berger;R. Margutti;G. Pooley;R. Sari;A. Soderberg;A. Brunthaler;M. Bietenholz;M. Bietenholz
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作者：
B. Zauderer;E. Berger;R. Margutti;G. Pooley;R. Sari;A. Soderberg;A. Brunthaler;M. Bietenholz;M. Bietenholz
本文对相对论性潮汐扰动事件Swift J164449.3+573451（Sw 1644+57）进行了持续600天的多频射电观测。这些数据是通过JVLA和AMI大型阵列获得的，作为我们正在进行的对干扰超大质量黑洞周围的喷流能量学和秒差距尺度环境的密度结构的研究的一部分。我们将这些数据与公开的Swift/XRT和Chandra X射线观测结果在同一时间框架内结合起来，表明喷流从1500天开始经历了一个戏剧性的转变，在δt/t ≥ 0.2的时间尺度上，X射线通量急剧下降约170倍（在δt/t ≥ 0.05的时间尺度上下降15倍）。快速下降排除了前向冲击源（直接或后处理）的X射线发射在0.500天，而是指向内部喷流的内部耗散。另一方面，我们的无线电数据独特地表明，钱德拉在610天测量到的低X射线通量与前向激波的发射一致。此外，钱德拉的数据与来自吸积盘本身的热辐射不一致，因为预期的温度为30-60 eV，内半径为12 -10 Rs，无法容纳观测到的通量水平或检测到的12 - 1 keV的辐射。我们将快速下降与相对论喷流的关闭联系起来，当质量吸积率下降到M/yr−1以下时（对于3 × 106 M/yr黑洞和阶数单位效率），表明峰值吸积率约为，到t/500天的总吸积质量约为0.15 M/yr。从射电资料中我们进一步发现，前向激波的积分能量在t_250天时明显变平，Ej，iso = 1054 erg（喷流张开角θj = 0.1时Ej = 1052 erg），在t_30 -250天时上升约15倍。展望未来，我们预测无线电和X射线波段的发射将以类似的下降率同步发展。
We present continued multi-frequency radio observations of the relativistic tidal disruption event Swift J164449.3+573451 (Sw 1644+57) extending to t ≈ 600 days. The data were obtained with the JVLA and AMI Large Array as part of our on-going study of the jet energetics and the density structure of the parsec-scale environment around the disrupting supermassive black hole. We combine these data with public Swift/XRT and Chandra X-ray observations over the same time-frame to show that the jet has undergone a dramatic transition starting at ≈500 days, with a sharp decline in the X-ray flux by about a factor of 170 on a timescale of δt/t ≲ 0.2 (and by a factor of 15 in δt/t ≈ 0.05). The rapid decline rules out a forward shock origin (direct or reprocessing) for the X-ray emission at ≲ 500 days, and instead points to internal dissipation in the inner jet. On the other hand, our radio data uniquely demonstrate that the low X-ray flux measured by Chandra at ≈610 days is consistent with emission from the forward shock. Furthermore, the Chandra data are inconsistent with thermal emission from the accretion disk itself since the expected temperature of ∼30–60 eV and inner radius of ∼2–10 Rs cannot accommodate the observed flux level or the detected emission at ≳ 1 keV. We associate the rapid decline with a turn off of the relativistic jet when the mass accretion rate dropped below M☉ yr−1 (for a 3 × 106 M☉ black hole and order unity efficiency) indicating that the peak accretion rate was about , and the total accreted mass by t ≈ 500 days is about 0.15 M☉. From the radio data we further find significant flattening in the integrated energy of the forward shock at t ≳ 250 days with Ej, iso ≈ 2 × 1054 erg (Ej ≈ 1052 erg for a jet opening angle, θj = 0.1) following a rise by about a factor of 15 at ≈30–250 days. Projecting forward, we predict that the emission in the radio and X-ray bands will evolve in tandem with similar decline rates.