Work

Delving into the depths of NGC 3783 with XRISM. VI. Evidence for a failed wind based on Fe XXV absorption line variability

Year: 2026

Type: article

Abstract: NGC 3783 exhibits a prominent absorption trough in the time-averaged XRISM/Resolve spectrum. To investigate its short-term variability, we present a time-resolved analysis of the absorption line during the continuous ten-day observation. We divided the resolved absorption profile into five fixed velocity intervals and measured their normalised equivalent widths (EWs) in 19 time-resolved spectra. Three velocity intervals exhibit significant EW variability. Two velocity intervals respond differently to low- and high-flux states with less emission line contamination. The time-dependent photoionisation modelling is unable to reproduce the most significant observed EW variation (3.5 , σ), possibly owing to uncertainties in the assumed initial equilibrium state, which prevent a precise density measurement. Instead, using photoionisation calculations and assuming the high-density limit, we derive approximate constraints on the ionisation parameters of the two relevant components. The low-velocity component (-320 to -680 Fe XXV Fe XXV km,s^ -1 ) shows a delayed inverse response, indicating a high ionisation parameter, while its relatively short lag timescale indicates a relatively high density and a distance upper limit of (0.05) pc. In contrast, the high-velocity component (-680 to -1040 ̊m km ,s^ -1 ) manifests a positive response with a longer lag to the ionising continuum, implying a relatively low ionisation parameter. This component appears to be less dense, with an inferred distance upper limit of 0.25 pc. The low-velocity component is consistent with a failed wind, as its outflow velocity is below the local escape velocity, whereas the high-velocity component lies near the escape threshold. Together with the lower-ionisation failed wind detected in 2001, this supports a multiphase failed-wind scenario in the unobscured state of NGC 3783 over more than two decades.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202661313