NASA-JAXA XRISM Mission Sees Pulsar Accreting Companion's 'Wind'

This artist’s concept of the BP Crucis system follows the pulsar on a passage through the dense stream of plasma flowing from its companion, a blue hypergiant 40 times the Sun’s mass. During each four-day passage, the pulsar’s X-ray brightness flares as it pulls in some of the gas. At first, the gas forms a messy, turbulent accretion disk around the pulsar, and plasma spirals down to it. But as the pulsar moves deeper into the stream, there’s not enough angular momentum to support the disk, and it breaks up. At this point, plasma falls straight onto the pulsar. Later, as the pulsar nears the end of its passage, a messy accretion disk rebuilds, this time spinning in the opposite direction of the earlier disk.

Credit: NASA’s Goddard Space Flight Center Conceptual Image Laboratory

Alt text: Animation of the BP Crucis system

0:00 A wide view, showing the giant star, its gas stream, and the pulsar nearing it.
0:08 The camera zooms into the pulsar as it encounters the stream.
0:10 Gas flowing past the pulsar forms a clockwise-spinning accretion disk.
0:17 The disk breaks up. The gas now flows directly onto the pulsar.
0:35 As the pulsar nears the end of its passage through the stream, a new disk, spinning counterclockwise, forms.
0:51 The disk breaks up and the pulsar exits the stream.
0:52 Return to a wide view of the system.

The Resolve instrument aboard the NASA-JAXA XRISM (X-ray Imaging and Spectroscopy Mission) observatory captured this high-resolution X-ray spectrum of BP Crucis. Prominent iron absorption lines (dashed) have shifted to lower energies (red lines), which indicates both the direction and velocity of the gas. The observations indicate the gas is moving toward the pulsar at about 335,000 mph (540,000 kph). Data and error bars are shown in gray, with a model spectrum in light blue. Roman numerals indicate the ionization state of iron atoms (the number of electrons they’ve lost to produce each spectral line).

Credit: NASA’s Goddard Space Flight Center, JAXA/NASA, Rahin et al. 2026

Alt text: XRISM Resolve absorption spectrum of BP Crucis

Image description: A light-blue line with many downward dips extends across a dark blue background with a darker tone at the bottom than the top. Behind it is a forest of gray lines marking data points and their error bars, following the ups and downs of the line. Dashed blue lines with blue labels above them extend down to the line. These labels are Roman numerals, from “XXI” to “XXVI.” The last label, at far right, covers two dashed lines, which are labeled “K-alpha 2” and “K-alpha 1.” Blue text above these labels reads “Laboratory line positions.” To the left of the blue dashed lines are solid red ones that connect to the most prominent dips in the light-blue line; a label above them reads “Observed line positions.” A yellow box illustrates how a blue dashed reference line has moved leftward to form the red line; it includes a large left-pointing arrow, labeled “Redshift,” shaded from blue on the right to red on the left. Yellow text to the right of the box reads “Redshifted absorption lines indicate gas falls toward the pulsar at about 335,000 mph (540,000 kph). Text at the top of the image reads “XRISM Resolve spectrum of GX 301-2.” Labels along the bottom axis read “Energy (keV)” and numbers from 6.5 to 7.0; the left axis reads “X-ray flux.”

In this artist’s concept of the BP Crucis system, the city-sized pulsar GX301-2 approaches a thick stream of gas flowing away from its massive partner, the blue hypergiant Wray 977. The pulsar flares up in X-rays twice each orbit when it encounters the stream.

Credit: NASA’s Goddard Space Flight Center Conceptual Image Laboratory

Alt text: Artist’s concept of BP Crucis

Image description: Against a hazy, star-filled sky, a brilliant bluish-white star shines near the center of this artist’s concept. From the star, at about 4 o’clock, an expanding stream of bluish gas arcs toward lower left and then sweeps toward bottom center as it moves into the foreground. Another bright star-like point, much smaller, shines near the stream, just right of the image’s center. It emits two long, thin, wedge-shaped beams of radiation. One emerges at about 2 o’clock and heads to the upper right, the other, emerging at 7 o’clock, heads toward lower left. Text reads “Artist’s concept.”

This artist’s concept illustrates how accretion by pulsar GX 301-2 changes as it traverses a dense plasma stream produced by its companion, which it encounters twice every orbit. As the pulsar gathers up this material, it erupts in powerful X-ray flares. Left: As the pulsar enters the stream, a turbulent accretion disk forms around it. Plasma spirals in a clockwise direction as it falls inward to reach the pulsar. Center: Moving deeper into the stream, the pulsar encounters a part of the flow that lacks the angular momentum needed to form a disk. The disk breaks up and plasma flows directly onto the pulsar. Right: The messy disk returns, now spinning in the opposite direction, as the pulsar nears the end of its journey through the stream.

Credit: NASA’s Goddard Space Flight Center Conceptual Image Laboratory

Alt text: Three-panel view of pulsar’s stream passage

Image description: Three vertical images, outlined in white, sit side-by-side on a dark blue background. Each image shows a bluish-white gas near a pulsar, shown as a white star-like object of varying brightness in the images. The pulsar has glowing, soft, wedge-shaped beams emanating from opposite sides. The beams change orientation in this sequence because the pulsar is rotating. At left, the pulsar sits in the middle of a stream that curls clockwise around it. At center, the pulsar has brightened, and the swirling gas now flows directly onto the object. At right, the pulsar appears fainter, and the gas is now swirling counterclockwise.

This artist’s concept illustrates the accretion style of pulsar GX 301-2 as it begins its passage through a dense plasma stream produced by its companion, which it encounters twice every orbit. As the pulsar gathers up this material, it erupts in powerful X-ray flares. As the pulsar enters the stream, a turbulent accretion disk forms around it. Plasma spirals in a clockwise direction as it falls inward to reach the pulsar.

Credit: NASAs Goddard Space Flight Center Conceptual Image Laboratory

Alt text: Visualization of pulsar's early stream passage.

Image description: On a dark background, bluish-white gas swirls clockwise near a pulsar (center), shown as a white star-like object of varying brightness. The pulsar has glowing, soft, wedge-shaped beams emanating from opposite sides, pointing toward the top and bottom of the image.

This artist’s concept illustrates the direct accretion of pulsar GX 301-2 in the middle of its passage through a dense plasma stream produced by its companion. By moving deeper into the stream, the pulsar encounters a part of the flow that lacks the angular momentum needed to form a disk. The disk breaks up and plasma flows directly onto the pulsar.

Credit: NASA’s Goddard Space Flight Center Conceptual Image Laboratory

Alt text: Visualization of pulsar’s direct accretion phase

Image description: On a dark background, bluish-white gas swirls near a pulsar (center), shown as a white star-like object of varying brightness. The pulsar has glowing, soft, wedge-shaped beams emanating from opposite sides, pointing toward the top and bottom of the image. It is immersed in a cloud of bluish-white gas that is falling directly onto it, with no accretion disk present.

This artist’s concept illustrates the final accretion phase of pulsar GX 301-2 near the end of its passage through a dense plasma stream produced by its companion. The messy accretion disk returns, now spinning in the opposite direction of the first disk, as the pulsar nears the end of its four-day journey through the stream.

Credit: NASA’s Goddard Space Flight Center Conceptual Image Laboratory

Alt text: Visualization of pulsar’s final accretion phase

Image description: On a dark background, bluish-white gas swirls counterclockwise near a pulsar (center), shown as a white star-like object of varying brightness. The pulsar has glowing, soft, wedge-shaped beams emanating from opposite sides, pointing toward the top and bottom of the image.