Nagoya University experts observe polarized X-rays from a black hole

A black hole binary star “Haku” observed by the X-ray polarization observation satellite IXPE (Imaging X-ray Polarimetry Explorer), an international joint project in which Ikuyuki Mitsuishi, a lecturer at the Graduate School of Science, Nagoya University, participates. The observation results of “Cygnus X-1” were published in the online version of the scientific journal “Science” dated November 4, 2022.
IXPE is the world’s first X-ray polarization imaging satellite, which was launched on December 9, 2021. From the observation of a black hole and a binary system of stars in the Milky Way, this research group is able to detect the X emitted from the vicinity of the black hole. We found that the lines were slightly polarized, and clarified the position and shape of the hot plasma (corona) near the black hole . Around the black hole in the black hole binary system, there is a spiral-shaped high-temperature “disk” formed by the strong gravitational pull of matter from the star and a plasma called “corona” that is hotter than the disk. To do. This time, the joint research group observed the black hole binary system Cygnus X-1, and found that the direction of X-ray oscillation was slightly biased toward the direction of the plasma jets emitted from the black hole. (polarized). This X-ray bias and intensity suggests that the corona is not in the direction of the jet, but instead covers both sides of the disk or is located between the inner edge of the disk and the black hole. Such a positional relationship of matter near the black hole is too far away to be resolved by conventional X-ray telescopes, and it was revealed for the first time by observing polarized light. The results of this research are expected to lead to the verification of the physics under strong gravitational fields near black holes and the measurement of the rotation speed of black holes.