Another way for stellar-mass black holes to grow larger

A trio of researchers with The University of Hong Kong, Academia Sinica Institute of Astronomy and Astrophysics in Taiwan and Northwestern University in the U.S., has come up with an alternative theory to explain how some stellar-mass black holes can grow bigger than others. In their paper published in The Astrophysical Journal Letters, Shu-Xu Yi, K.S. Cheng and Ronald Taam describe their theory and how it might work.

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Credit: NASA/CXC/M.Weiss

This artist's impression shows a binary system containing a stellar-mass black hole called IGR J17091-3624, or IGR J17091 for short.

The strong gravity of the black hole, on the left, is pulling gas away from a companion star on the right.

This gas forms a disk of hot gas around the black hole, and the wind is driven off this disk.


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This animation compares the X-ray 'heartbeats' of GRS 1915 and IGR J17091, two black holes that ingest gas from companion stars. GRS 1915 has nearly five times the mass of IGR J17091, which at three solar masses may be the smallest black hole known. A fly-through relates the heartbeats to hypothesized changes in the black hole's jet and disk.

But to date only IGR J17091 and one other system, named GRS 1915+105, exhibit so-called rho-class oscillations that astronomers describe as a 'heartbeat' reflecting the accretion and ejection of matter.

It's thought that strong magnetic fields near the black hole's event horizon eject some of the gas into dual, oppositely directed jets that blast outward at nearly the speed of light.