What are stellar winds? Observing a neutron star gives us a unique insight

The NASA Chandra

NASA’s Chandra X-ray Observatory has recorded data of a neutron star passing through a dense patch of stellar wind. This has provided an insight into the structure and composition of stellar winds, and more about the properties of the neutron star.

The neutron star observed by the NASA Chandra is part of a high-mass X-ray binary system of an incredibly dense neutron star together with a massive supergiant star. By watching the neutron star pass through a stellar wind, the research team found that, contrary to previous research, stellar winds are made up of dense clumps.

What is a neutron star?

The neutron stars in binary systems create X-rays when material from their companion star, the massive supergiant star, follows towards them and is accelerated to high velocities. The X-rays which are produced as a result of this acceleration can interact with stellar winds to produce secondary X-rays at various distances away from the neutron star.

The spectrometer on the Chandra is able to capture these X-rays and separate them based on their energy, allowing astronomers to learn more about star compositions.

The structure and composition of stellar winds

The lead author of the paper and a postdoctoral researcher in astronomy and astrophysics at Penn State, Pragati Pradhan, explained: “Stellar winds are the fast-flowing material–composed of protons, electrons, and metal atoms–ejected from stars. This material enriches the star’s surroundings with metals, kinetic energy, and ionizing radiation. It is the source material for star formation. Until the last decade, it was thought that stellar winds were homogenous, but these Chandra data provide direct evidence that stellar winds are populated with dense clumps.”

Pradhan continued:”In this work, we see a dimming of the X-rays from the neutron star and a prominent line from neutral iron in the X-ray spectrum–two signatures supporting the clumpy nature of stellar winds… We expect to be able to improve our understanding of these phenomenon with the upcoming launch of spacecrafts like Lynx and Athena, which will have improved X-ray spectral resolution.”

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