A Fast X-ray Disk Wind in the Transient Pulsar IGR J17480-2446 in Terzan 5

TL;DR

This paper reports the detection of a fast, blue-shifted disk wind in the transient pulsar IGR J17480-2446, revealing similarities to black hole winds and providing insights into accretion processes and magnetic field strengths.

Contribution

First detection of a fast disk wind in a transient pulsar, showing similarities to black hole winds and suggesting disk truncation by magnetic fields.

Findings

Blue-shifted Fe XXV and Fe XXVI absorption lines indicating a wind

Wind velocity of approximately 3100 km/s and 1000 km/s

Inner disk possibly truncated with magnetic field strength of 0.7-4.0 x 10^9 Gauss

Abstract

Accretion disk winds are revealed in Chandra gratings spectra of black holes. The winds are hot and highly ionized (typically composed of He-like and H-like charge states), and show modest blue-shifts. Similar line spectra are sometimes seen in "dipping" low-mass X-ray binaries, which are likely viewed edge-on; however, that absorption is tied to structures in the outer disk, and blue-shifts are not typically observed. Here we report the detection of blue-shifted He-like Fe XXV (3100 +/- 400 km/s) and H-like Fe XXVI (1000 +/- 200 km/s) absorption lines in a Chandra/HETG spectrum of the transient pulsar and low-mass X-ray binary IGR J17480-2446 in Terzan 5. These features indicate a disk wind with at least superficial similarities to those observed in stellar-mass black holes. The wind does not vary strongly with numerous weak X-ray bursts or flares. A broad Fe K emission line is detected in the spectrum, and fits with different line models suggest that the inner accretion disk in this system may be truncated. If the stellar magnetic field truncates the disk, a field strength of B = 0.7-4.0 E+9 Gauss is implied, which is in line with estimates based on X-ray timing techniques. We discuss our findings in the context of accretion flows onto neutron stars and stellar-mass black holes.