NASA's Imaging X-ray Polarimetry Explorer (IXPE) has advanced understanding of black hole structures, particularly the accretion disk and corona surrounding them. Observations of the stellar-mass black hole in the binary system Swift J1727.8-1613, discovered during a brightening event in summer 2023, have provided new insights into X-ray binary behavior.
The black hole's outburst, which outshone nearly all X-ray sources, was the first of its kind observed by IXPE, capturing data throughout the event's progression. Alexandra Veledina, an astrophysicist at the University of Turku, noted the rapid evolution of the outburst, stating it peaked within days of initial detection.
Swift J1727, located 8,800 light years from Earth, exhibited an unprecedented brightness, surpassing the Crab Nebula, a standard reference for X-ray brightness. Such binary systems typically consist of two stars, where the elder star's supernova leaves behind a neutron star, white dwarf, or black hole, which then strips material from its companion star, generating X-rays.
IXPE specializes in measuring X-ray polarization, essential for mapping the structures around black holes. Veledina emphasized that direct observation of black holes is impossible due to their gravity, making IXPE's work crucial for understanding their environments.
Studies led by Veledina and Adam Ingram focused on the initial phases of the outburst, revealing that the corona was the primary source of observed X-ray radiation. IXPE documented polarization aligned with the black hole jet's direction, confirming similar geometrical findings in other black hole systems.
Further research by Jiří Svoboda and Jakub Podgorný examined polarization during the later stages of the outburst, indicating consistent corona geometry despite significant changes in X-ray brightness. These findings mark a substantial advancement in the comprehension of black hole structures and demonstrate IXPE's potential in collaborative cosmic monitoring.