Gravastar Shadows
Gravastar Shadows
复制标题
格拉瓦星阴影
DOI：
10.1103/physrevd.90.104013
复制
发表时间：
2014
期刊：
影响因子：
--
通讯作者：
玉置孝至
中科院分区：
文献类型：
--
作者：
坂井伸之;斉田浩見;玉置孝至
直接观测黑洞是天文学面临的重大挑战之一。然而，如果有超致密物体具有不稳定的光子圆形轨道，通过观察光子可能很难将它们与黑洞区分开来。作为超致密天体的一个模型，我们考虑由Mazur和Mottola最先提出的引力真空星。为了确定，我们采用了Visser和Wiltshire提出的球面薄壳模型，它连接了内部的de Sitter几何和外部的Schwarzschild几何。我们发现，不稳定的圆形光子轨道可以出现在坡度星周围。然后，我们研究了具有不稳定圆轨道的梯度星的光学图像，假设它的光学透明表面和梯度星背后的两种光源：(I)无限大的光学平面和(Ii)伴星。(I)图像的主要特征是在该区域的中心出现一个明亮的圆盘和一个围绕该圆盘的深厚的环，如果致密物体不是格瓦斯塔星而是Schwarzschild黑洞，该区域将是完全黑暗的。同样在情况(Ii)中，一个小圆盘和圆盘周围的弧线出现在施瓦西德黑洞的透镜图像完全黑暗的区域。因为在这两种情况下，特征图像都出现在葡萄牙星的内部，我们可以在不久的将来通过高分辨率的超长基线干涉观测来区分黑洞和葡萄牙星。
Direct observation of black holes is one of the grand challenges in astronomy. If there are supercompact objects which possess unstable circular orbits of photons, however, it may be difficult to distinguish them from black holes by observing photons. As a model of supercompact objects, we consider a gravastar (gravitational-vacuum-star) which was originally proposed by Mazur and Mottola. For definiteness, we adopt a spherical thin-shell model of a gravastar developed by Visser and Wiltshire, which connects interior de Sitter geometry and exterior Schwarzschild geometry. We find that unstable circular orbits of photons can appear around the gravastar. Then, we investigate the optical images of the gravastar possessing unstable circular orbits, assuming its optically transparent surface and two types of optical sources behind the gravastar: (i) an infinite optical plane and (ii) a companion star. The main feature of the image of (i) is that a bright disk and a dark thick ring surrounding the disk appear in the center of the region which would be completely dark if the compact object was not the gravastar but the Schwarzschild black hole. Also in case (ii), a small disk and arcs around the disk appear in the region which would be completely dark for the lensing image by the Schwarzschild black hole. Because characteristic images appear inside the gravastar in both cases, we could tell the difference between a black hole and a gravastar with high-resolution very-long-baseline-interferometry observations in the near future.