An Iron K Component to the Ultrafast Outflow in NGC 1313 X-1

TL;DR

This paper reports the detection of an iron K absorption feature in NGC 1313 X-1, indicating an ultrafast outflow with velocities around 0.2-0.25c, supporting the super-Eddington accretion hypothesis.

Contribution

First detection of an iron K component in the ultrafast outflow of NGC 1313 X-1, linking it to previously observed lower-energy outflows and suggesting extreme accretion conditions.

Findings

Detected an absorption feature at 8.77 keV with 3σ significance.

Outflow velocity estimated at ~0.2c to 0.25c, consistent with ultrafast outflows.

Supports super-Eddington accretion scenario for NGC 1313 X-1.

Abstract

We present the detection of an absorpton feature at $E=8.77^{+0.05}_{-0.06}$ keV in the combined X-ray spectrum of the ultraluminous X-ray source NGC 1313 X-1 observed with XMM-Newton and NuSTAR, significant at the 3$\sigma$ level. If associated with blueshifted ionized iron, the implied outflow velocity is ~0.2$c$ for Fe XXVI, or ~0.25$c$ for Fe XXV. These velocities are similar to the ultrafast outflow seen in absorption recently discovered in this source at lower energies by XMM-Newton, and we therefore conclude that this is an iron component to the same outflow. Photoionization modeling marginally prefers the Fe XXV solution, but in either case the outflow properties appear to be extreme, potentially supporting a super-Eddington hypothesis for NGC 1313 X-1.