XRISM Captures Stellar Wind Feeding Pulsar in BP Crucis, Illuminating X‑ray Flare Mechanism

Using the Resolve spectrometer on the NASA‑JAXA XRISM observatory, astronomers directly observed ionized iron absorption lines shifting to lower energies, indicating plasma from the blue hypergiant Wray 977 is falling onto its neutron‑star companion, GX 301‑2. The gas rushes toward the pulsar at roughly 335,000 mph (540,000 kph), a speed inferred from the redshift of the lines. XRISM’s data were collected during a 16‑hour window near the end of a strong X‑ray flare, when the pulsar’s turbulent accretion disk collapses and matter streams straight onto the neutron star. The observations confirm that the pulsar’s X‑ray brightness spikes as it captures the companion’s stellar wind, providing the first clear spectroscopic evidence of wind‑fed accretion in a high‑mass X‑ray binary. The findings, published in Science Advances, enable detailed testing of models that describe how massive stars lose mass and how compact objects accrete that material.