Zombie Star's Cosmic 'Fart' Triggers X-Ray Flares
Neutron star flares up when passing through hypergiant's plasma plume.
1Unusual binary star system
The BP Crucis system, located 13,000 light-years from Earth, consists of a blue hypergiant star (Wray 977) 60 times larger than our sun and a neutron star (GX 301-2). This neutron star is a pulsar - an ultradense stellar remnant only 20km across but containing a sun's worth of mass. It emits regular beams of electromagnetic radiation that flash Earth every 11 minutes, unlike typical pulsars that maintain consistent brightness.
2Mysterious X-ray flares
GX 301-2 exhibits irregular X-ray flares separate from its regular pulses, shining significantly brighter at repeated intervals. Researchers long suspected these flares occurred when the neutron star interacted with stellar wind from its massive companion, but lacked direct evidence. The flares coincide with the neutron star's closest and farthest orbital points around Wray 977, with strongest activity during closest approach every 41.5 days.
3Groundbreaking observations
NASA and JAXA's XRISM space telescope captured detailed spectra during a 16-hour observation of a flare event. The data revealed rapidly changing emission and absorption lines showing plasma from Wray 977's stellar wind interacting with GX 301-2. This marks the first direct observation of stellar wind plasma accretion onto a compact object, with the hypergiant emitting a concentrated plasma plume at 540,000 km/h.
4Plasma accretion mechanism
The observations showed how dense stellar wind plasma swirls around and accumulates on the neutron star's surface. When sufficient material builds up, it triggers explosive flashes detectable from Earth. The plasma plume's shape appears influenced by the neutron star's gravity, forming a single concentrated stream rather than dispersing uniformly. Researchers simulated exactly how the plasma falls onto and interacts with the passing neutron star.
5Scientific significance
This discovery provides the first clear evidence of wind plasma accretion onto a compact stellar remnant, opening new avenues for studying similar systems. BP Crucis serves as an ideal laboratory for understanding wind-fed pulsar accretion processes. The detailed spectral data allows scientists to test and refine models of extreme stellar interactions with unprecedented precision, advancing knowledge of high-energy astrophysical phenomena.
6XRISM's capabilities
The X-ray Imaging and Spectroscopy Mission (XRISM), a collaborative NASA-JAXA project, proved uniquely capable of capturing the rapid plasma dynamics. Its high-resolution spectra revealed previously unobservable details of the plasma-neutron star interaction. Researchers emphasize XRISM's ideal instrumentation for advancing understanding of accretion processes, with plans to study future flaring events in BP Crucis and similar systems.
7Hypergiant's extreme wind
Wray 977 emits a stellar wind far more extreme than our sun's solar wind. The blue hypergiant produces a single, focused plume of ionized gas moving at 335,000 mph. This contrasts with the sun's more dispersed solar wind that creates auroras. The neutron star's gravity likely shapes the hypergiant's wind into this concentrated stream, demonstrating how binary systems can dramatically alter stellar behaviors.
8Future research directions
The team plans further XRISM observations to better understand the relationship between GX 301-2 and Wray 977's plasma plume. Future studies will examine how varying orbital positions affect accretion intensity and flare characteristics. This system provides a template for investigating other wind-fed pulsars, potentially revealing new classes of high-energy stellar interactions and testing fundamental astrophysical theories.
Original article: Latest from Live Science — Zombie Star's Cosmic 'Fart' Triggers X-Ray Flares