This animation illustrates how new pulsars are found by analysing Fermi data. The LAT detector onboard Fermi records the precise arrival time and the celestial direction for each gamma photon registered. But in order to identify a pulsar, it is necessary to have not only a significantly more precise position in the sky, but also its period of rotation, and the rate at which the rotation slows down. Since the pulsars are so far away, only few gamma photons are detected – only one photon per 100,000 rotations.
The team at the Albert Einstein Institute in Hanover carried out a so-called blind search using new analytical methods. Computers were used to investigate many different combinations of positions and rotational characteristics to see whether they agree with the arrival times of the photons in the Fermi telescope from the appropriate direction. The search involved analysing several thousand photons detected within three years. If the arrival times of the photons agree with the exact position and the rotational model of the pulsar, a regular pattern is produced in the count of the gamma photons. This means a new pulsar has been discovered.
credit: Max Planck Institute