The current state of disk wind observations in BHLMXBs through X-ray absorption lines in the iron band

Abstract

The presence of blueshifted absorption lines in the X-ray spectra of black hole low-mass X-ray binaries is the telltale mark of massive outflows called winds. These signatures are found almost exclusively in soft states of high-inclined systems, hinting at equatorial ejections originating from the accretion disk and deeply intertwined with the evolution of the outburst patterns displayed by these systems. In the wake of the launch of the new generation of X-ray spectrometers, studies of wind signatures remain mostly restricted to single sources and outbursts, with some of the recent detections departing from the commonly expected behaviors. We thus give an update to the current state of iron band absorption line detections through the analysis of all publicly available XMM-Newton-pn and Chandra-HETG exposures of known black hole low-mass X-ray binary candidates. Our results agree with previous studies, as our wind detections are exclusively found in dipping, high-inclined sources and almost exclusively in bright (LX > 0.01LEdd) soft (HR < 0.8) states with blueshift values generally restricted to a few 100 km s−1. The line parameters indicate similar properties between objects and outbursts of single sources, and despite more than 20 yr of data, very few sources have the HID sampling necessary to properly study the evolution of the wind during a single outburst. We provide an online tool with details of the wind signatures and outburst evolution data for all sources in our sample.