Repeating outbursts of 40,000-degree wind discovered near black hole
The same system showed signs of a violent outburst in 2011. Then, it happened again in 2017. But this time, scientists noticed the repetitive behavior and took a look with the largest telescope in the Southern Hemisphere, the South African Large Telescope.
In the system, there’s a low-mass star like our sun and a black hole compact object that’s six times the mass of the sun.
The black hole compact object is pulling material from the star into a disk that separates the two of them. When the star’s material grows hot, it becomes unstable. This is the cause of the energetic outbursts, the researchers said.
In 2011, the researchers noticed dips in the system’s brightness, which shifted as the outburst evolved — not something they had observed before.
“But what really astonished us was the discovery that these spectral features were visible only during the optical dips in the light-curve,” Charles said. “We have interpreted this quite unique property as due to a warp or ripple in the inner accretion disc that orbits the black hole on the dipping timescale. This warp is very close to the black hole at just 1/10 the radius of the disc.”
The wind is moving toward Earth rather than the black hole, and the researchers believe this is due to the pressure of the radiation being generated by X-rays so close to the black hole.
Such intense radiation should appear brighter than it does in the spectral data, but the black hole is pulling in material that probably obscures the light from our view. We’re also looking at the system’s edge, rather than head-on, because of its orientation.
Studying this intriguing system will allow astronomers to learn more about the end of star evolution and the formation of compact objects, like neutron stars, white dwarfs and black holes.
“These short-period binary versions are a perfect way to study this physics in action,” Charles said.