Astronomers detect new neutron star

Paris, Dec 22: A new type of neutron star has been detected by the XMM-Newton Science Operations Centre’s European Photon Imaging Camera (EPIC).

Astronomers observed the weird new type of star for around 12 hours and detected periodic X-ray emission coming from it.

Previously, astronomers had only seen radio outbursts from this object. It erupts every three minutes or so with a brief burst of radio emission lasting just 3 milliseconds. Such behaviour defines the object as a rotating radio transient (RRAT).

Astronomers had suspected that the new celestial object was a neutron star, which is the compact remnant of dead stars made of neutrons and measuring just 10-12 km across yet containing more matter than the Sun.

Most observed neutron stars are radio pulsars; rotating quickly and sweeping lighthouse beams of radiation across space that make them appear to pulsate. The new star, however, was only detected through their radio bursts.

Detected pulsations in the X-ray data show the source of the emission (i.e. the newly discovered star) to be rotating once every 4.26 seconds.

The new XMM-Newton observations show that periodic emission, linked to the object’s rotation, can be detected in X-rays.

"It is now definite that RRATs are rotating neutron stars as we can see the 4.26-second rotation period of the RRAT in the X-ray data," said Maura McLaughlin, West Virginia University, USA, who took the lead in the research.

In addition to the identification of the underlying celestial object from the discovery of the X-ray pulsations, XMM-Newton also revealed another facet of the RRAT’s behaviour. Something appears to be absorbing certain frequencies of the X-rays after they are emitted from the surface of the neutron star.

The absorption could either be happening in an atmosphere of gases surrounding the neutron star or by particles trapped in the neutron star’s magnetic field. If the second reason is the cause of the absorption, it would indicate that the magnetic field of this RRAT is strong.

“We can’t say for sure where the absorption is coming from with these observations,” said Nanda Rea from University of Amsterdam, Netherlands. According to her, an observation twice as long would collect enough data to determine where the absorption is taking place.

The research team is hoping to follow-up this observation by targeting other RRATs with radio telescopes across the world, timing the outbursts. From careful measurements of the arrival times of the bursts over the course of the year, their positions in the sky can be determined more accurately. Once these locations are known, X-ray telescopes can be pointed in their direction.

Since the original discovery of 11 RRATs, McLaughlin’s team has found an additional 10. This indicates that they may form a substantial population in the Milky Way, with over 100 000 of them dotted around our galaxy. (ANI)