光学亮相对论潮汐破裂事件AT 2022 cmc的线性和圆偏振测量
Linear and circular polarimetry of the optically bright relativistic Tidal Disruption Event AT 2022cmc
摘要：
当一颗恒星绕着一个巨大的黑洞运行时，它离黑洞足够近，以至于被黑洞以潮汐的方式撕裂，就会发生潮汐破裂事件（TDE）。AT 2022 cmc是第一个被观测到（并发现）的相对论性TDE，它是一个光学上明亮和快速的瞬变，显示出由朝向地球的喷流引起的非热辐射的特征。在这项工作中，我们提出了光学线性和圆偏振测量，观察VLT/FORS 2在$R$ -波段（对应于蓝色/UV部分的光谱在休息帧），$\sim$ 7.2和$\sim$ 12.2休息帧天后，第一次检测，分别时，光变曲线的瞬态已解决在一个明亮的蓝色平台。线偏振和圆偏振均与零一致，$p_{lin}$ = 0.14 $\pm$ 0.73%和$p_{cir}$ = $-$ 0.30 $\pm$ 0.53%。这是最高的S/N线性偏振测量获得的相对论性TDE和第一个圆偏振这样的瞬态。线偏振和圆偏振的未检测与AT 2022 cmc是TDE的情况一致，其中热分量（盘+流出）被视为极上，假设轴对称几何形状。然而，射流和/或外部冲击的存在和影响很难理清。
英文摘要：
Tidal disruption events (TDEs) occur when a star orbiting a massive black hole is sufficiently close to be tidally ripped apart by the black hole. AT 2022cmc is the first relativistic TDE that was observed (and discovered) as an optically bright and fast transient, showing signatures of non-thermal radiation induced by a jet which is oriented towards the Earth. In this work, we present optical linear and circular polarization measurements, observed with VLT/FORS2 in the $R$-band (which corresponds to the blue/UV part of the spectrum in rest frame), $\sim$ 7.2 and $\sim$ 12.2 rest-frame days after the first detection, respectively, when the light curve of the transient had settled in a bright blue plateau. Both linear and circular polarization are consistent with zero, $p_{lin}$ = 0.14 $\pm$ 0.73 % and $p_{cir}$ = $-$0.30 $\pm$ 0.53 %. This is the highest S/N linear polarization measurement obtained for a relativistic TDE and the first circular polarimetry for such a transient. The non detection of the linear and circular polarization is consistent with the scenario of AT 2022cmc being a TDE where the thermal component (disk+outflows) is viewed pole-on, assuming an axially symmetric geometry. The presence and effect of a jet and/or external shocks are, however, difficult to disentangle.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
