Observations of Stellar Mass Black Holes

Henric Krawczynski (Washington University in St. Louis)

January 08, 2026

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Abstract: NASA and ESA launched the Imaging X-Ray Polarimetry Explorer (IXPE) in 2021, and our group has launched the balloon-born hard X-ray polarimeter XL-Calibur in 2024. The two missions observe extreme objects such as stellar mass and supermassive black holes, neutron stars in different environments, and magnetars and perform for the first time precision measurements of their polarization in the 2-8 keV (IXPE) and 15-60 keV (XL-Calibur) energy bands. I will describe the two missions, and discuss the results obtained for Black Holes in X-ray binaries with regards to their implications for how black holes accrete matter. My talk will emphasize what we know about the properties of the region from which the emission originates, and what the X-ray polarimetry observations tell us about the background spacetime, the properties of the emitting plasma, and the micro and macro plasma processes that lead to the observed X-ray energy spectra and polarization.