The physics behind the ionization structure of outflows from black holes is yet to be fully understood. Using archival observations with the Chandra/HETG gratings over the past two decades, we measured an absorption measure distribution for a sample of outflows in nine active galactic nuclei (AGNs), namely the dependence of outflow column density, N H, on the ionization parameter, ξ. The slope of log N H versus log ξ is found to be between 0.00 and 0.72. We find an anticorrelation between the log of total column density of the outflow and the log of AGN luminosity, and none with the black hole mass and accretion efficiency. A major improvement in the diagnostics of AGN outflows will potentially occur with the launch of the XRISM/Resolve spectrometer. We study the ability of Resolve to reveal the outflow ionization structure by constructing the absorption measure distribution from simulated Resolve spectra, utilizing its superior resolution and effective area. Resolve constrains the column density as well as HETG, but with much shorter observations.

Supernovae (SNe) are responsible for the elemental enrichment of the galaxy [1, 2]. High-mass core-collapse SNe are postulated to leave behind a black hole (BH) [3, 4]. In a stellar binary the BH can accrete back its own debris, emit X-rays, and eject winds [5]. Measuring abundances of elements in the outflow, or of the companion [6, 7], can lead to inferences about the historical explosion and identify the long-gone progenitor of the black hole [8]. Here, we exploit a uniquely rich X-ray spectrum of the binary GRO J1655-40 [9-11] to measure seventeen different elements in its wind. The wind is unusually rich in odd-Z elements, such as Na, Al, P, Cl, and K. Such a composition has been predicted for core-collapse SNe of metal-rich massive stars of 40 M⊙ [12, 13], but never before observed. The ionization distribution in the wind [14, 15] features two distinct regions, which reflect changes in its radial profile, and perhaps entrainment of pristine circumstellar supernova debris. It can also explain why the wind differs in composition from that of the stellar companion, where SN debris is mixed with its atmosphere [7]. The difference between the current BH mass of 6.6 M⊙ and theoretical estimates for its birth mass of ∼ 3 M⊙ date the supernova at least 10 million years back if it grew by accretion.