Scientists may have discovered something unusual in the universe. They've found two black holes devouring their companion stars and kicking out matter with winds at speeds of around a quarter of the speed of light.
When you look at the universe at X-ray wavelengths, you're likely to see two types of astronomical objects: supermassive black holes and binary systems. Supermassive black holes can usually be found sitting at the centers of large galaxies and devouring material around them. Binary systems usually consist of a white dwarf, neutron star or black hole feeding off gas from a companion star.
With that said, an intermediate class of objects was found in the 1980s. Ten to 100 times brighter than ordinary X-ray binaries, the objects are still too faint to be linked to supermassive black holes.
"We think these so-called 'ultra-luminous x-ray sources' are special binary systems, sucking up gas at a much higher rate than an ordinary x-ray binary," said Ciro Pinto from Cambridge University and one of the researchers involved in the new study. "Some of these sources host highly magnetized neutron stars, while others might conceal the long-sought-after intermediate-mass black holes, which have masses around one thousand times the mass of the sun. But in the majority of cases, the reason for their extreme behavior is still unclear."
In this latest study, the researchers looked at three ultra-luminous X-ray sources located in galaxies that were less than 22 million light-years from the Milky Way. In all three sources, the researchers were able to identify X-ray emission from gas in the outer portions of the disc surrounding the central compact object, slowing flow toward it.
For two of the three sources, though, the researchers saw clear signs of X-rays being absorbed by gas streaming away from the central source at almost a quarter of the speed of light.
"This is the first time we've seen winds streaming away from ultra-luminous X-ray sources," Pinto said. "And the very high speed of these outflows is telling us something about the nature of the compact objects in these sources, which are frantically devouring matter."
The findings reveal a bit more about these sources and also show how they behave. The winds, in particular, may tell researchers a bit more about the forces at work in these X-ray sources.
The findings are published in the April edition of the journal Nature.
