Expected evolution of disk wind properties along an X-ray binary outburst

Abstract

Blueshifted X-ray absorption lines (preferentially from Fe XXV and Fe XXVI present in the 6–8 keV range) indicating the presence of massive hot disk winds in black hole (BH) X-ray binaries (XrB) are most generally observed during soft states. It has been recently suggested that the nondetection of such hot wind signatures in hard states could be due to the thermal instability of the wind in the ionization domain consistent with Fe XXV and Fe XXVI. Studying the wind thermal stability does require, however, a very good knowledge of the spectral shape of the ionizing spectral energy distribution (SED). In this paper, we discuss the expected evolution of the disk wind properties during an entire outburst by using the RXTE observations of GX 339-4 during its 2010–2011 outburst. While GX 339-4 never showed signatures of a hot wind in the X-rays, the dataset used is optimal for the analysis shown in this study. We computed the corresponding stability curves of the wind using the SED obtained with the jet-emitting disk model. We show that the disk wind can transit from stable to unstable states for Fe XXV and Fe XXVI ions on a day timescale. While the absence of wind absorption features in hard states could be explained by this instability, their presence in soft states seems to require changes in the wind properties (e.g., density) during the spectral transitions between hard and soft states. We propose that these changes could be partly due to the variation of the heating power release at the accretion disk surface through irradiation by the central X-ray source. The evolution of the disk wind properties discussed in this paper could be confirmed through the daily monitoring of the spectral transition of a high-inclination BH XrB.

Winds and Disk Turbulence Exert Equal Torques on Thick Magnetically Arrested Disks

“…Our nonradiative simulations are most appropriate for modeling the hard state of X-ray binaries, which are believed to host strongly magnetized radiatively inefficient accretion flows (Ferreira et al 2006;Remillard & McClintock 2006;Marcel et al 2019). The absence of X-ray absorption lines during the hard state does not imply the disappearance of winds, but rather indicates changes in the ionization of the wind due to alterations in the flux of ionizing X-ray photons from the disk (Chakravorty et al 2013;Petrucci et al 2021). This interpretation is supported by the detection of blueshifted near-infrared absorption lines during complete state transitions, exhibiting similar properties during both the hard and soft states (Sánchez-Sierras & Muñoz-Darias 2020).…”

Determining the Orbital Period and Wind Geometry in GRO J1655–40

“…However, this state dependence is still not fully understood, especially given the discovery of winds in the optical and near-infrared at all outburst phases (e.g., Muñoz-Darias et al 2016;Sánchez-Sierras & Muñoz-Darias 2020;Muñoz-Darias & Ponti 2022). The appearance and production of X-ray winds may be due to changes between state transitions, such as the launching mechanism or mass-loss rate (e.g., Neilsen & Homan 2012;Tomaru et al 2019;Higginbottom et al 2020), but a combination of photoionization and thermodynamic stability considerations (e.g., Chakravorty et al 2013;Petrucci et al 2021) may be more plausible in light of the multiphase nature of these outflows (e.g., Neilsen & Degenaar 2023). A better understanding of winds and their evolution can lead to more knowledge about spectral states and the reasons behind this dependence.…”

A unified accretion-ejection paradigm for black hole X-ray binaries

“…In addition to these two jets, strong winds are usually detected, especially in the soft states (see, e.g., Ponti et al 2012). However, it is still unclear exactly when these winds are produced and observed (see introduction in Petrucci et al 2021).…”