Max Planck Institute for Gravitational Physics | 2015 Aug 05
Max Planck Scientists Discover Elusive Gamma-ray Pulsar with Distributed Computing Project Einstein@Home
[c][attachment=0]standard_sans_both.jpg[/attachment][/c]Gamma-ray pulsars are remnants of explosions that end the lives of massive stars. They are highly-magnetized and rapidly rotating compact neutron stars. Like a cosmic lighthouse they emit gamma-ray photons in a characteristic pattern that repeats with every rotation. However, since only very few gamma-ray photons are detected, finding this hidden rhythm in the arrival times of the photons is computationally challenging. Now, an international team led by researchers at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) in Hannover, Germany, has discovered a new gamma-ray pulsar hidden in plain sight in data from the Fermi Gamma-ray Space Telescope. The improved, adaptive data analysis methods and the computing power from the distributed volunteer computing project Einstein@Home were key to their success.
Searching for an Elusive Gamma-ray Pulsar
The gamma-ray source in which the discovery was made was thought to be a pulsar from the year 2012 on, based on the energy distribution of the gamma-ray photons observed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. For years, it was one of the brightest Fermi-LAT catalogue sources without a known association. “Everyone believed that the source now known as PSR J1906+0722 was a pulsar. The tricky part was to show that the gamma-ray photons carry the imprint of the pulsar's rotation and arrive according to that hidden rhythm. Many had tried that before, but to no avail,” says Holger Pletsch, leader of an independent research group at the AEI and co-author of the paper that now appeared in The Astrophysical Journal Letters.
The Fermi-LAT observations cover a total time of more than six years now. For every single gamma-ray photon received from the pulsar, the AEI scientists had to identify during which of the up to billions of pulsar rotations it was emitted. Since a priori there is very little knowledge about the pulsar's rhythm and its other properties, vast parameter spaces have to be searched very finely – otherwise the hidden signal would be missed. “It's a lot like searching the proverbial needle in haystack, except that beforehand we don't even know what our needle exactly looks like,” says Colin Clark, PhD student in Pletsch's group and lead author of the paper. ...
PSR J1906+0722: An Elusive Gamma-ray Pulsar - C. J. Clark et al
- Astrophysical Journal Letters 809(1) L2 (10 Aug 2015) DOI: 10.1088/2041-8205/809/1/L2
arXiv.org > astro-ph > arXiv:1508.00779 > 04 Aug 2015