Polarization patterns of the hot spots plunging into a Kerr black hole
Bin Chen, Yehui Hou, Yu Qin Song, Zhenyu Zhang
Abstract
The multiwavelength polarized light signals from supermassive black holes have sparked many studies on polarized images of accretion disks and hot spots. However, the polarization patterns within the innermost stable circular orbit (ISCO) region remain to be explored. In this study, we focus on two specific types of orbits, namely the plunging geodesics inward from the ISCO and homoclinic geodesics, to uncover the polarization features associated with noncircular motion in a Kerr spacetime. For an on-axis observer, we specifically develop an approximate function to describe gravitational lensing along the azimuthal direction and establish a simplified synchrotron emission model. Based on these, we analyze the time-integrated polarized images of hot spots and their Stokes parameters. Moreover, we explore the polarized image of the plunging region within a thin accretion disk.