Radio Observations of an Ordinary Outflow from the Tidal Disruption Event AT2019dsg
Radio Observations of an Ordinary Outflow from the Tidal Disruption Event AT2019dsg
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DOI：
10.3847/1538-4357/ac110a
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发表时间：
2021-03
期刊：
影响因子：
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通讯作者：
Y. Cendes;K. Alexander;E. Berger;T. Eftekhari;P. G. Williams;R. Chornock
中科院分区：
文献类型：
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作者：
Y. Cendes;K. Alexander;E. Berger;T. Eftekhari;P. G. Williams;R. Chornock
本文介绍了利用卡尔G. Jansky甚大阵列（VLA）和阿塔卡马大型毫米/亚毫米阵列（阿尔马），并跨越55-560天后中断。我们发现射电辐射的峰值亮度一直增加到200天，然后开始稳定地下降。使用标准的均分分析，包括由联合VLA-ALMA光谱能量分布确定的同步加速器冷却的影响，我们发现，为射电发射提供动力的外流大致处于自由膨胀状态，速度为10.07 c，而其动能从55到200天增加约5倍，此后在104.4 × 1048 erg处达到平台。外流所追踪到的环境密度以半径<$R −1.7下降，范围为<$（1-4）× 1016 cm（<$6300 - 25，000 R s），然后急剧下降到<$7 × 1016 cm（<$44，000 R s）。考虑到准直几何，我们发现，要达到甚至是温和的相对论速度（Γ = 2），外流需要θ j <$2 °的开口角，即使以伽马射线暴喷流的标准来看，这也是很窄的;真正的相对论外流需要非物理上窄的喷流。AT 2019 dsg的外流速度和动能是以前非相对论性TDE的典型特征，与Ib/c型超新星的速度和动能相当，这让人怀疑它与高能中微子事件的关联。
We present detailed radio observations of the tidal disruption event (TDE) AT2019dsg, obtained with the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA), and spanning 55–560 days post disruption. We find that the peak brightness of the radio emission increases until ∼200 days and subsequently begins to decrease steadily. Using a standard equipartition analysis, including the effects of synchrotron cooling as determined by the joint VLA–ALMA spectral energy distributions, we find that the outflow powering the radio emission is in roughly free expansion with a velocity of ≈0.07 c, while its kinetic energy increases by a factor of about 5 from 55 to 200 days and plateaus at ≈4.4 × 1048 erg thereafter. The ambient density traced by the outflow declines as radius ≈R −1.7 on a scale of ≈(1–4) × 1016 cm (≈6300–25,000 R s ), followed by a steeper decline to ≈7 × 1016 cm (≈44,000 R s ). Allowing for a collimated geometry, we find that to reach even mildly relativistic velocities (Γ = 2) the outflow requires an opening angle of θ j ≈ 2°, which is narrow even by the standards of gamma-ray burst jets; a truly relativistic outflow requires an unphysically narrow jet. The outflow velocity and kinetic energy in AT2019dsg are typical of previous non-relativistic TDEs, and comparable to those from type Ib/c supernovae, raising doubts about the claimed association with a high-energy neutrino event.