'Jekyll and Hyde' Star Morphs From X-Ray To Radio Pulsar
Sep 25, 2013 04:31 PM EDT
Researchers have found a star with the never-before-seen ability to morph between X-ray and radio pulsars, it had been cleverly dubbed the "Jekyll and Hyde" star.
The star's unusual behavior seems to be influenced by a nearby star, and could help explain the birth of millisecond pulsars, a National Radio Astronomy Observatory press release reported via e Science News.
"What we're seeing is a star that is the cosmic equivalent of 'Dr. Jekyll and Mr. Hyde,' with the ability to change from one form to its more intense counterpart with startling speed," Scott Ransom, an astronomer at the National Radio Astronomy Observatory (NRAO), said.
"Though we have known that X-ray binaries -- some of which are observed as X-ray pulsars -- can evolve over millions of years to become rapidly spinning radio pulsars, we were surprised to find one that seemed to swing so quickly between the two," he said.
Neutron stars are incredibly dense remains of past-exploded supernovas. This two-faced neutron is 18,000 light-years away in the Sagittarius constellation. Researchers had noticed the existence of the star for years, but were unsure of exactly what it was.
"Various observations of one particular star over the years and with different telescopes have revealed vastly different things -- at one time a pulsar and the other an X-ray binary," lead author Alessandro Papitto of the Institute of Space Sciences, said. "This was particularly intriguing because radio pulses don't come from an X-ray binary and the X-ray source has to be long gone before radio signals can emerge."
X-ray binaries are part of a two-star system consisting of a neutron star and one with a lower mass.
"The smaller but considerably more massive neutron star can draw off material from its companion, forming a flattened disk of gas around the neutron star. Gradually, as this material swirls down to the surface of the neutron star, it becomes superheated and generates intense X-rays," the press release stated.
The researchers believed this accretion process went on for millions of years, but could one day run out of materials, stopping the X-ray process.
Researchers noticed that X-ray "outbursts" would last for about a month and then suddenly stop only to return again days later. The neutron's powerful magnetic fields that create radio waves, the waves "sweep "across space creating a light-house like appearance.
The discovery shows that evolution may occur in short bursts, instead of gradually over time.
"This not only demonstrates the evolutionary link between accretion and rotation-powered millisecond pulsars," Ransom, said "but also that some systems can swing between the two states on very short timescales."