2026/07/21 by Arghajit Jana, Claudio Ricci, Franz E. Bauer +13
#astro-ph.GA #astro-ph.HE
The bolometric luminosity (L\rm bol) of active galactic nuclei (AGNs) is a key tracer of accretion physics, but its direct determination is often hindered by limited spectral coverage and contamination of the host galaxy. Bolometric corrections (κλ = L\rm bol/Lλ) offer a practical means of estimating L\rm bol, with the X-ray bolometric correction (κ\rm 2-10) being crucial for exploring the coupling between the accretion disk and the X-ray corona. Here we present multi-epoch, multi-wavelength observations of five highly variable, changing-state AGNs that span more than three orders of magnitude in Eddington ratio (-3.6\lesssim log λ\rm Edd \lesssim -0.5). This unique data set reveals a remarkably tight relation between κ\rm 2-10 and λ\rm Edd, with an intrinsic scatter of only ∼0.05 dex. We find that while the sources show bolometric corrections following different tracks in luminosity space that depend on black hole mass, they all display the same κ\rm 2-10-λ\rm Edd trend. This shows unambiguously that λ\rm Edd is the primary driver of X-ray bolometric corrections, and points to a tight underlying trend that can be used to obtain reliable estimates of bolometric output from X-ray luminosities. Our results highlight how time-domain, multi-wavelength observations of variable AGN offer unique insights into the accretion flow structure and its radiative output.