First Year of Stellar-Mass Black Hole Observations with the Imaging X-ray Polarimetry Explorer

The Imaging X-ray Polarimetry Explorer (IXPE), launched on December 9, 2021, enables X-ray polarimetric observations with unprecedented sensitivity in the 2-8 keV energy range. X-ray polarization allows us to test the processes in accretion disks and coronae of stellar-mass black holes in X-ray binaries found in both soft and hard spectral states. Every state is characterized by a combination of thermal disk, coronal, or reflected emission—each type containing different information about the environment around the black hole that can be understood through polarization. In 2022, IXPE measured the polarization signatures of four stellar-mass black holes: Cygnus X-1, 4U 1630-47, Cygnus X-3, and LMC X-1. We report on the physical consequences of these first IXPE observations and the science driven by this new chapter in X-ray polarimetry.