U of A prof involved in explosive discovery

A University of Alberta astronomer may have helped discover an entirely new class of explosive event in space, as part of a global research team.

The still-unknown objects erupt with X-rays, spontaneously flaring up to 100 times brighter than normal and then returning to their original X-ray levels. The flare-ups happen in less than a minute and return to normal after about an hour.

X-rays like this are generated from extremely hot temperatures, up to the equivalent of “millions of degrees Celsius,” said Gregory Sivakoff, a U of A researcher who co-authored the study that will appear in Nature.

The team has come up with a number of explanations for the source of the flares, with the most likely being that they are caused by matter from a nearby star falling into black holes or neutron stars.

Black holes and neutron stars are extremely compact remnants of stars and a neutron star contains the entire mass of a star in an area the size of Edmonton, said Sivakoff. A black hole is even smaller.

When the material from the star rubs into a disc around the neutron star or black hole, it gets extremely hot and then falls, creating the Xrays. Sivakoff said a disruption in the system may be causing a large amount of material to fall at once, which causes a rush of X-rays and creates the massive flare-ups.

Due to the extreme brightness of the eruption, the team has named them “ultraluminous X-ray bursts.” The researchers say these type of flares have been important to astronomy in the past and they hope this will be the case again. For example, some supernovas were essential for understanding how the universe is expanding and how material that created life spread.

“To our knowledge, this behaviour is new, unexplored phenomena,” said Sivakoff.

The study had 11 authors from 10 international institutions. The discovery was made using NASA’s Chandra X-ray observatory and the European Space Agency’s XMMNewton observatory.

The two telescopes are orbiting in space and each organization accepts proposals from researchers who are interested in using them.