In this present work, we study the observational appearance of Kerr-Melvin black hole (KMBH) illuminated by an accretion disk. The accretion disk is assumed to be located on the equatorial plane and to be thin both geometrically and optically. Considering the fact that outside the innermost stable circular orbit (ISCO) the accretion flow moves in prograde or retrograde circular orbit and falls toward the horizon along plunging orbit inside the ISCO, we develop the numerical backward ray-tracing method and obtain the images of KMBH accompanying with the accretion disk for various black hole spins, strengths of magnetic fields, and inclination angles of observers. We present the intensity distribution horizontally and longitudinally and show the profiles of the redshift for the direct and lensed images. Our study suggests that the inner shadow and critical curves can be used to estimate the magnetic field around a black hole without degeneration.

中文翻译：

---

带有薄吸积盘的克尔-梅尔文黑洞图像

在目前的这项工作中，我们研究了吸积盘照亮的克尔-梅尔文黑洞 (KMBH) 的观测外观。假设吸积盘位于赤道平面上并且在几何和光学上都很薄。考虑到在最内稳定圆轨道（ISCO）外吸积流在顺行或逆行的圆轨道上运动并沿ISCO内的俯冲轨道落向地平线，我们开发了数值反向射线追踪方法并获得了KMBH的图像伴随着吸积盘，用于各种黑洞自旋、磁场强度和观察者倾角。我们呈现水平和纵向的强度分布，并显示直接和透镜图像的红移轮廓。