论文标题
射手座A*的EHT观察之后，无视对象的约束*
Constraints on horizonless objects after the EHT observation of Sagittarius A*
论文作者
论文摘要
事件地平线望远镜合作最近发布的Sagittarius A $^*$的图像伴随着[ap.j.lett. \ \，{\ bf 930 \，\＃2} \，（2022）\，（2022）\，（l17]），通过对置于置物的限制的分析，可能会陷入困境。超紧凑型物体，表面重新发射入射辐射。实际上，使用观察到的图像大小和sgr a $^*$的宽带光谱，据称，任何此类热表面的半径都受这些最新观察结果的强烈界定。在本文中，我们讨论了报告的约束如何取决于积聚磁盘和中心物体之间能量交换中完美平衡的极强假设，并表明每当表面赋予任何非零吸收系数时，这会违反。我们详细讨论可以在表面的半径和无量纲吸收系数上施放的上限约束。我们表明，EHT协作提供的分析的结论仅适用于吸收系数的不自然值（即低于$ 10^{ - 14} $），因此在具有物理意义的情况下必须进行显着修订。
The images of Sagittarius A$^*$ recently released by the Event Horizon Telescope collaboration have been accompanied [Ap.J.Lett.\,{\bf 930\,\#2}\,(2022)\,L17] by an analysis of the constraints on the possible absence of a trapping horizon, i.e.~on the possibility that the object at the center of our galaxy is an ultra-compact object with a surface re-emitting incident radiation. Indeed, using the observed image size and the broadband spectrum of Sgr A$^*$, it is claimed that the radius of any such thermal surface is strongly bounded from above by these latest observations. Herein, we discuss how the reported constraint relies on the extremely strong assumption of perfect balance in the energy exchange between the accretion disk and the central object, and show that this is violated whenever the surface is endowed with any non-zero absorption coefficient. We discuss in detail the upper-bound constraints that can be cast on the radius and dimensionless absorption coefficient of the surface. We show that the conclusions of the analysis presented by the EHT collaboration hold only for unnaturally small values of the absorption coefficient (i.e. much lower than $10^{-14}$), and thus have to be significantly revised in scenarios with physical significance.
