Overview

• The XRISM collaboration reports in Nature that its Resolve instrument captured a thick, multi‑phase outflow from the neutron‑star binary GX13+1 during a super‑Eddington brightening on February 25, 2024.
• Despite the extreme luminosity, the wind speed was about 1 million km/h, far slower than ultrafast active galactic nucleus winds that can reach 20–30% of light speed.
• XRISM’s high‑resolution X‑ray spectroscopy measured the wind’s velocity, density and structure, revealing a smooth flow that contrasts with the clumpy AGN winds seen in earlier XRISM results.
• The team suggests that cooler, ultraviolet‑dominated disks around supermassive black holes may push matter more efficiently than the hotter, X‑ray‑dominated disks in stellar binaries.
• XRISM is a JAXA‑led mission with NASA and ESA, and the findings are guiding follow‑up observations, new modeling efforts and planning for future high‑resolution X‑ray missions such as NewAthena.