An Eddington-limited Accretion Disk Wind in the Narrow-line Seyfert 1 PG 1448+273

PG 1448+273 is a luminous, nearby (z = 0.0645), narrow-line Seyfert 1 galaxy, which likely accretes close to the Eddington limit. Previous X-ray observations of PG 1448+273 with XMM-Newton in 2017 and NuSTAR in 2022 revealed the presence of an ultrafast outflow, as seen through its blueshifted iron (Fe) K absorption profile, where the outflow velocity appeared to vary in the range 0.1‑0.3c. In this work, new X-ray observations of PG 1448+273 are presented, in the form of four simultaneous XMM-Newton and NuSTAR observations performed in 2023 July and August. The X-ray spectra appeared at a similar flux in each observation, making it possible to analyze the mean 2023 X-ray spectrum at high signal-to-noise ratio. A broad (σ = 1 keV) and highly blueshifted (E = 9.8 ± 0.4 keV) Fe K absorption profile is revealed in the mean spectrum. The profile can be modeled by a fast, geometrically thick accretion disk wind, which reveals a maximum terminal velocity of v _∞ = ‑0.43 ± 0.03c, one of the fastest known winds in a nearby active galactic nucleus. As a result, the inferred mass outflow rate of the wind may reach a significant fraction of the Eddington accretion rate.