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A neutron star was found to have a dense, fog-like wind — a discovery that challenges current theories.
Abstract
Accretion disks in strong gravitational fields commonly produce winds, observed as blueshifted absorption lines in the X-ray band. The most powerful of these (Eddington winds) are expected from systems with luminosity near the Eddington limit, where radiation pressure can strip material from the inner disk. The Resolve spectrometer aboard XRISM detected one of the densest winds ever seen in absorption lines in the binary system with the neutron star GX 13+1. This Compton-thick wind substantially absorbs the flux, making the system appear dim even though its true luminosity exceeds the Eddington limit. However, the wind speed is extremely low, which agrees with models of thermal radiation winds launched by X-ray irradiation of the outer disk regions, rather than with the expected Eddington wind driven by radiation pressure from within. This imposes new constraints on the origin of winds in bright binary systems and contrasts with ultra-fast (v ~ 0.3c) winds recently detected by Resolve from a supermassive black hole with a similarly high Eddington ratio.
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When a companion star pulls matter onto a neutron star, a whirlwind of scorching gas swirls around it. From this, streams erupt — a stellar wind. It was thought that with bright radiation, the wind should race at nearly the speed of light. But the XRISM telescope, examining the light with spectroscopy, showed otherwise.
The wind from GX 13+1 turned out to be not a hurricane, but a dense fog: record-breakingly thick and unexpectedly slow. A speed close to light was expected, but the stream moves thousands of times slower. This can't be explained by light pressure — it's likely pushed out by heating of the outer disk regions.
The dense fog dims the star's visible brilliance, making it fainter.
The discovery forces a rethink of how neutron stars and black holes return matter to the galaxy, influencing the birth of new stars. The contrast with winds from supermassive black holes, flying nearly at light speed, emphasizes that both fog and hurricane coexist in space.
🎯 Neutron stars were theoretically predicted by [scientist:Fritz Zwicky]Fritz Zwicky[/scientist] in 1934, and the first observational confirmation came in 1967 when [scientist:Jocelyn Bell Burnell]Jocelyn Bell Burnell[/scientist] discovered pulsars.
