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Contenu archivé le 2024-06-18

Large European Array for Pulsars

Final Report Summary - LEAP (Large European Array for Pulsars)

The Large European Array for Pulsars (LEAP) established novel techniques to increase the sensitivity of radio astronomical observations in order to detect Einstein’s gravitational waves. The method used is the timing of signals from cosmic light houses, so called radio pulsars. These are relatively weak radio sources, the observations of which demand the biggest available telescopes. With LEAP, it is possible to combine the collective power of Europe’s most powerful telescopes in order to simulate the sensitivity of a 200-m diameter dish! With such sensitivity, we aim to measure the small variations in the arrival time of the pulsars’ signal that is caused by the changing space-time around Earth, when the planets “reacts” to a passing gravitational wave. These waves are believed to travel the Universe from a distant past, when smaller galaxies formed big ones like the Milky Way. As the Earth “moves”, it effectively changes the distance of the Earth to the pulsars, resulting in a different pulse arrival time at the European telescopes. With LEAP we have achieved a sensitivity that corresponds to a change in distance of about 100m over 1 lightyear. It seems that the effect of the gravitational waves is still smaller than that, but with LEAP observations conducted one per month, the scientists are confident that LEAP will finally allow them to detect and measure a background of overlapping gravitational wave signals.

We are pleased to report that all Work Packages (WP) are complete. We have achieved what we set out for:

1) We have developed new techniques and methods to combine the collective power of Europe’s largest radio telescope (which also represent 5 of the 8 largest telescopes in the world) to form a huge 200-m dish equivalent array for pulsar observations.

2) We have developed new hardware and recording systems, which were used to take data with the array in monthly observing sessions since July 2011. For a year now, we were able to observe with full sensitivity using also the new Sardinia Radio Telescope.

3) We have developed new methods to precisely calibrate our data and produce timing measurements that are far more precise than those obtained by single telescopes. We also developed and established new algorithms and method to optimise and schedule observations.

4) The data have been used to conduct a variety of science projects. Most importantly, we derived a new upper limit for the amplitude of a stochastic gravitational wave background. This limit, currently based on a limited data set, is already better than those available at the beginning of the project. Data are still coming, so that the data analysis will continue, and we expect to improve the limit significantly further. The LEAP team will continue to work jointly on this endeavour, even though most have or are in the process of taking on new appointments.

5) We also studied a variety of theoretical questions related to source finding, source characterisation and their use for studies of the fundamental properties of gravitons.

6) We have employed LEAP hardware also beyond the measurements of pulse times of arrival by obtaining imaging and also scattering observations of the newly discovered magnetar in the Galactic Centre.

7) We have completed also the other work packages and continued our links with the gravitational wave and SKA communities and industry.