XRISM Observatory Detects Stellar Wind Powering Pulsar X-ray Flares

• Astronomers using the Japan-led XRISM observatory have directly observed a pulsar capturing stellar wind from its companion star, fueling intense X-ray flares.
• The findings reveal the complex dynamics of matter transition from a hypergiant star to a dense neutron star, providing new insights into accretion processes.

The BP Crucis System

• The system consists of Wray 977, a blue hypergiant 40 times the Sun's mass, and GX 301-2, a neutron star (pulsar) about 12 miles across.
• The pulsar orbits the primary star every 41.5 days, experiencing significant X-ray flares as it traverses the dense plasma stream emitted by the hypergiant.

Observational Findings

• NASA and JAXA’s Resolve instrument captured high-resolution X-ray spectra during a 16-hour observation on Feb. 1, 2025.
• Redshift analysis of iron absorption lines indicates that plasma is racing toward the pulsar at approximately 335,000 mph (540,000 kph).

Accretion Dynamics

• As the pulsar enters the stellar wind, it initially forms a turbulent accretion disk that powers the observed flares.
• As the pulsar penetrates deeper into the flow, the disk dissipates due to a lack of sufficient angular momentum, leading to direct plasma inflow onto the neutron star surface.
• The system exhibits a four-day transit period, during which the structure of the gas inflow changes dynamically, briefly forming a reverse-spinning disk before exiting the stream.