Chandra spots X-ray emissions unlike any seen before

TUSCALOOSA, Ala., Oct. 19 (UPI) -- Chandra has located two sources of mysterious X-ray flares unlike any seen before. The sources were found in two separate elliptical galaxies.

During an X-ray pulse, the flare grows increasingly bright for about a minute. At the flare's peak it gives off thousands of times more X-rays than a binary star system -- qualifying the two objects as ultraluminous X-ray sources.

"These flares are extraordinary," Peter Maksym, a researcher at the Harvard-Smithsonian Center for Astrophysics, said in a news release. "For a brief period, one of the sources became one of the brightest ULX to ever be seen in an elliptical galaxy."

One of the X-ray sources -- seen in an image captured by Chandra -- is found in the galaxy NGC 5128, also known as Centaurus A. NGC 5128 is located 12 million light-years from Earth. The home of the other source is NGC 4636, situated 47 million light-years from Earth.

The only phenomenon comparable to the newly discovered X-ray sources are the X-ray flares emitted by magnetars, neutron stars with strong magnetic fields.

Magnetars are typically found among aging stars in sparsely populated regions of space. Astronomers believe the mysterious new sources are likely positioned within densely populated stellar clusters.

Researchers described the mysterious X-ray sources in a new paper, published this week in the journal Nature.

Astronomers don't yet have an explanation for the X-ray pulses, but scientists have begun offering hypotheses.

"Now that we've discovered these flaring objects, observational astronomers and theorists alike are going to be working hard to figure out what's happening," said study co-author Gregory Sivakoff, an astronomer at the University of Alberta.

Researchers suggest the flares could be caused by interactions between a dying neutron star and its companion. Another possibility includes the accretion of matter by an intermediate-mass black hole.