Resolving a Clumpy Disk Wind in 4U 1957+115 with XRISM
Abstract
We present a high-resolution XRISM/Resolve observation of the persistent black hole candidate 4U 1957+115, revealing the first detection of an intrinsic disk wind in this source. The absorption is dominated by highly ionized Fe XXV and Fe XXVI and varies substantially throughout the observation, becoming prominent during the final ∼40 ks despite a modest decrease of only ∼5--10% in source flux. The observed evolution of the absorption cannot be explained solely by ionization changes driven by the modest continuum variability, favoring an inhomogeneous outflow with evolving line-of-sight properties. Time-resolved spectroscopy reveals substantially narrower absorption features in shorter intervals, with the inferred turbulent velocity decreasing from ∼350 km/s in the longer integration to ≲70 km/s in the shortest selections. This suggests that the broader absorption profiles measured over longer integrations may result, at least in part, from averaging over an evolving wind rather than from intrinsically larger turbulent velocities. Such time averaging can therefore affect the inferred physical properties of the wind and complicate efforts to identify its launching mechanism. Even though the wind carries only a small fraction of the radiative luminosity in kinetic form, its mass-loss rate may remain dynamically relevant. These results highlight the importance of time-resolved, high-resolution X-ray spectroscopy for characterizing the structure and variability of accretion disk winds.
Related
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BibTeX
@misc{draghis2026resolving,
title = {{Resolving a Clumpy Disk Wind in 4U 1957+115 with XRISM}},
author = {Paul A. Draghis and Erin Kara and Ehud Behar and Jon M. Miller and Vera Berger and Joheen Chakraborty and Peter Kosec and Christos Panagiotou and Swati Ravi and Fatima Zaidouni},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.34478},
eprint = {2610.34478},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.34478},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Resolving a Clumpy Disk Wind in 4U 1957+115 with XRISM
AU - Paul A. Draghis
AU - Erin Kara
AU - Ehud Behar
AU - Jon M. Miller
AU - Vera Berger
AU - Joheen Chakraborty
AU - Peter Kosec
AU - Christos Panagiotou
AU - Swati Ravi
AU - Fatima Zaidouni
PY - 2026
DA - 2026/10/25
PB - arXiv
DO - 10.48550/arxiv.2610.34478
UR - https://arxiv.org/abs/2610.34478
AB - We present a high-resolution XRISM/Resolve observation of the persistent black hole candidate 4U 1957+115, revealing the first detection of an intrinsic disk wind in this source. The absorption is dominated by highly ionized Fe XXV and Fe XXVI and varies substantially throughout the observation, becoming prominent during the final ∼40 ks despite a modest decrease of only ∼5--10% in source flux. The observed evolution of the absorption cannot be explained solely by ionization changes driven by the modest continuum variability, favoring an inhomogeneous outflow with evolving line-of-sight properties. Time-resolved spectroscopy reveals substantially narrower absorption features in shorter intervals, with the inferred turbulent velocity decreasing from ∼350 km/s in the longer integration to ≲70 km/s in the shortest selections. This suggests that the broader absorption profiles measured over longer integrations may result, at least in part, from averaging over an evolving wind rather than from intrinsically larger turbulent velocities. Such time averaging can therefore affect the inferred physical properties of the wind and complicate efforts to identify its launching mechanism. Even though the wind carries only a small fraction of the radiative luminosity in kinetic form, its mass-loss rate may remain dynamically relevant. These results highlight the importance of time-resolved, high-resolution X-ray spectroscopy for characterizing the structure and variability of accretion disk winds.
ER -