What Resolve held onto
GX 301-2 is an 11-minute pulsar ploughing through the stellar wind of Wray 977. On 2025-02-01, XRISM's Resolve spectrum showed highly ionized iron absorption shifted to lower energy than a laboratory rest frame — a redshift. That shift says the plasma is moving away from the observer, toward the pulsar, at about 540000 km/h (about 335000 mph). The Science Advances write-up appeared on Friday; the pointing lasted about 16 hours.[1]
BP Crucis sits about 13000 light-years away. Wray 977 is about 40 times the Sun's mass and 60 times its size; GX 301-2 is about 20 kilometres across. On the 41.5-day orbit, flares lasting several days rise near closest and farthest approach. The measurement puts wind plasma on the fuel line of those flares in the spectrum itself, rather than inferring the fuel only from orbital timing.[1]
The disk breakdown is a reading
The team proposes that a turbulent disk forms as the pulsar enters the stream, collapses when the stream no longer supplies the angular momentum to keep a disk, and lets plasma fall straight onto the neutron star, then briefly returns spinning the other way on the way out. The transit lasts about 4 days. The redshift lines give the inflow direction; the disk story is a mechanism fitted to how the spectrum evolved. Another geometry — slower gas in a shell farther from the pulsar — could still carry the same redshift.[1]
Roi Rahin says the team had not seen so clear a mark of wind plasma falling onto a compact object. That tightens the search: wind-fed pulsar models now face a resolved absorption speed, not only a light curve. A second Resolve spectrum at the same orbital phase would show whether the proposed reverse spin returns.[1]