渐近安全引力下的黑洞阴影和光环

Shadow and photon ring of black hole in asymptotically safe gravity

重点讨论了薄盘吸积与渐近安全(asymptotically safe,AS)引力修正参数对黑洞阴影和光环的影响.对于薄盘吸积,黑洞的暗区就是黑洞的阴影,而明亮的光环则是由直接像、透镜环和光子环组成的.对于吸积盘辐射源比强度,考虑了3个不同辐射轮廓模型.对辐射起始于最内圆轨道的二阶衰减函数模型,直接像、透镜环和光子环可以明显区分.直接像对黑洞光环亮度贡献最大,透镜环对光环亮度贡献很小,而光子环的贡献几乎可以忽略,且对应观测强度的峰值随AS引力参数的增加而减小,即对应光环亮度随修正参数的增大而变暗.对于辐射起始于光子球半径的三阶衰减函数模型,透镜环和光子环叠加在直接像上,使观测强度出现新的极值.这一极值随AS引力修正参数的增加而增加,且使得黑洞光环的亮度更亮.对辐射起始于事件视界的反三角衰减函数模型,透镜环和光子环在直接像上的叠加范围更大,观测到的光环更宽,且AS引力参数值越小,透镜环和光子环越难区分,黑洞光环的亮度越大.总之,研究表明,黑洞阴影半径的大小随AS修正参数的增加而减小,对于不同的AS引力修正参数,辐射源光强度、尤其是观测强度的辐射轮廓存在显著差异,导致黑洞的阴影和亮环明显不同.

In this paper,we discuss the influence of thin disk accretion and asymptotically safe(AS)gravity correction parameters on the shadow and photon ring of black hole.For the thin disk accretion,the dark region is the shadow of the black hole,and the bright photon ring is composed of direct image,lensing ring,and photon ring.For the specific intensity of the radiation source of the accretion disk,we consider three different emission profile models.For the second-order attenuation function model in which the emission starts from the innermost circular orbit,direct image,lensing ring,and photon ring can be clearly distinguished.The direct image contributes most of the brightness,and the lensing ring contributes a small portion,while the contribution of the photon ring can almost be ignored.And the observed corresponding intensity peak decreases with the increase of the AS gravity parameter,that is,the corresponding brightness of the photon ring darkens as correction parameter increases.For the third-order attenuation function model in which the emission begins at the radius of the photon sphere,lensing ring and photon ring are superimposed on the direct radiation.Thus a new extreme value of the observed intensity emerges,and the extreme value increases with the increase of the AS gravity parameter,which leads to a brighter observed photon ring.For the anti-trigonometric attenuation function model in which the radiation starts from the event horizon,the superposition range of lensing ring and photon ring on the direct radiation becomes larger,which makes photon ring wider.The smaller the AS gravity parameter,the more difficult it is to distinguish between the lensing ring and photon ring,and the brighter the photon ring turns.In short,the results show that the shadow radius decreases with the increase of the AS correction parameter.For different AS gravity correction parameters,the light intensities of emission source,especially emission profiles of the observed intensity are significantly different,resulting in obvious differences in observed emission intensity between the shadow of the black hole and the bright photon ring of the black hole.