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Young neutron star experienced tremendous hiccup during fastest rotation

Max Planck scientists have discovered a young and energetic neutron star with an unusually irregular rotation.

Washington: Max Planck scientists have discovered a young and energetic neutron star with an unusually irregular rotation.

Pulsars are superlative cosmic beacons. These compact neutron stars rotate about their axes many times per second, emitting radio waves and gamma radiation into space.

Using ingenious data analysis methods, researchers from the Max Planck Institutes for Gravitational Physics (MPG) and for Radio Astronomy (MPIfR), in an international collaboration, dug a very special gamma-ray pulsar out of data from the Fermi Gamma-ray Space Telescope.

The pulsar J1838-0537 is radio-quiet, very young, and, during the observation period, experienced the strongest rotation glitch ever observed for a gamma-ray-only pulsar.

The name of the newly discovered pulsar-J1838-0537 -- comes from its celestial coordinates.

“The pulsar is, at 5,000 years of age, very young. It rotates about its own axis roughly seven times per second and its position in the sky is towards the Scutum constellation. After the discovery we were very surprised that the pulsar was initially only visible until September 2009. Then it seemed to suddenly disappear,” said Holger Pletsch, a scientist in Allen`s group and lead author of the study.

Only a complex follow-up analysis enabled an international team led by Pletsch to solve the mystery of pulsar J1838-0537: it did not disappear, but experienced a sudden glitch after which it rotated 38 millionths of a Hertz faster than before.

“This difference may appear negligibly small, but it``s the largest glitch ever measured for a pure gamma-ray pulsar,” explained Bruce Allen, Director of the Albert Einstein Institute (AEI), whose team announced the discovery of nine new Fermi gamma-ray pulsars, back in November 2011. And this behavior has consequences.

“If the sudden frequency change is neglected, then after only eight hours, a complete rotation of the pulsar is lost in our counting, and we can no longer determine at which rotational phase the gamma-ray photons reach the detector aboard Fermi,” added Pletsch.

The “flashing” of the neutron star then disappears. If the researchers take the glitch into account and correct the change in rotation, the pulsar shows up again in the observational data.

The precise cause of the glitches observed in many young pulsars is unknown. Astronomers consider “star quakes” of the neutron star crust or interactions between the superfluid stellar interior and the crust to be possible explanations.

“Detecting a large number of strong pulsar glitches makes it possible to learn more about the inner structure of these compact celestial bodies,” said Lucas Guillemot from the Max Planck Institute for Radio Astronomy in Bonn, the second author of the study.
After the discovery in data from the Fermi satellite, the researchers pointed the radio telescope in Green Bank, West Virginia/USA at the celestial position of the gamma-ray pulsar. In an observation of almost two hours and by analyzing a further, older, one-hour observation of the source they found no indications of pulsations in the radio range, indicating that J1838-0537 is a rare gamma-ray-only pulsar.

The discovery has been which has now been published.


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