Though Miles Apart, One in Heart: X-ray Insights into Super-Eddington AGN Across Cosmic Times

Understanding how supermassive black holes (SMBHs) rapidly grew in the early Universe is a central question in extragalactic astrophysics. Here I present X-ray studies of super-Eddington (S-E) accreting active galactic nuclei (AGN) across cosmic epochs, combining results from local Narrow-Line Seyfert 1 (NLS1) galaxies and hyper-luminous quasars at z > 6. Broadband X-ray spectral analyses with NuSTAR, XMM-Newton, and Swift show that local S-E AGN have steep continua, low coronal temperatures, and strong reflection components. IRAS 04416+1215, the most extreme source in our sample and in the local Universe (?_Edd = 427), exhibits a coronal temperature of ~3 keV—the lowest ever measured in an AGN. At the opposite end of cosmic time, X-ray observations of z > 6 quasars from the HYPERION sample reveal very steep photon indices and fast UV-driven winds. Leveraging ~700 hours of XMM-Newton observations, we detect a strong correlation between the X-ray photon index and C IV blueshift in 18 luminous QSOs, suggesting a tight link between coronal physics and disc wind kinematics. These findings indicate that early QSOs likely accreted in the S-E regime throughout their formation history. Despite their separation in cosmic time, these QSOs show converging X-ray properties when accreting at high rates. Our results highlight the physical continuity of super-Eddington accretion across ~13Gyr, suggesting that low-z NLS1s offer key insights into the growth of the first QSOs.