Hercules X-1 is an X-ray binary system in which a neutron star is drawing material away from a Sun-like star. This neutron star’s accretion disk is unique in that it wobbles as it rotates. By taking advantage of this wobble, astronomers have captured varying perspectives of the rotating disk and created a 2D map of its winds.
Despite their existence being known for decades, the driving mechanism of accretion disk winds is still poorly understood.
In supermassive black holes, these outflows can even be powerful enough to dictate the evolution of the entire host galaxy, and yet so far astronomers do not understand whether they are launched by radiation pressure, magnetic forces, thermal irradiation or a combination thereof.
Clues to a wind’s origins may be deduced from its structure, but the shape and extent of disk winds has been difficult to resolve.
Most binaries produce accretion disks that are relatively even in shape, like thin donuts of gas that spins in a single plane.
Astronomers who study these disks from far-off satellites or telescopes can only observe the effects of disk winds within a fixed and narrow range, relative to their rotating disk.
Any wind that astronomers manage to detect is therefore a small sliver of its larger structure.
“We can only probe the wind properties at a single point, and we’re completely blind to everything around that point,” said Dr. Peter Kosec, an astronomer at MIT’s Kavli Institute for Astrophysics and Space Research.
In 2020, Dr. Kosec and his colleagues realized that Hercules X-1, a nearly edge-on X-ray binary with a warped accretion disk precessing with a period of about 35 days, could offer a wider view of disk winds.
“The disk is really wobbling over time every 35 days, and the winds are originating somewhere in the disk and crossing our line of sight at different heights above the disk with time,” Dr. Kosec said.
“That’s a very unique property of this system which allows us to better…
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