A failed wind candidate in NGC 3783 from the 2001 campaign with Chandra/HETGS

¹ Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
² SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
³ Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637, USA
⁴ MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
⁵ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

^⋆ Corresponding author; cli@strw.leidenuniv.nl

Received: 6 November 2024
Accepted: 15 January 2025

Abstract

We reanalyse the Chandra/HETGS observations of NGC 3783 from the campaign in the year 2001 and identify significant spectral variations in the Fe unresolved transition array (UTA) over timescales of weeks to months. These changes correlate with a 1.4− to two-fold increase in the ionising continuum and exceed 10σ significance. The variations primarily originate from a low-ionisation state (log ξ = 1.65) component of the warm absorber. Time-dependent photoionisation modelling confirmed the sensitivity of this low-ionisation component to continuum variations within the Fe UTA band. Local fitting indicated a lower density limit of > 10^12.3 m⁻³ at a 3σ statistical uncertainty, with the component located within 0.27 pc. Our findings suggest that this low-ionisation component is a potential failed wind candidate.