Gravitational waves and gravitational theories
The timing of an array of ultra-stable pulsars works like a giant galactic detector to observe gravitational waves in the nano-Hertz domain. The timing of pulsars in compact binary systems also enables stringent tests of gravitation theories in the strong field regime.
Neutron star population and emission mechanisms
Since 2006, we have been involved in the preparation and support of gamma-ray pulsar observations with the Large Area Telescope (LAT) on board the Fermi satellite. The NRT's "high energy" programmes represent 1200 hours of telescope time per year, with about 200 pulsars regularly monitored, and are coordinated internationally. NRT, LOFAR and NenuFAR observations also enable us to search for new pulsars in the Milky Way.
Tests of fundamental Physics: Electromagnetism
Although gravitational waves were recently detected for the first time by LIGO/Virgo, the understanding of the universe will still be based on electromagnetic waves for a long time to come. 96% of the universe being unknown to us (dark matter and dark energy), the role of fundamental Physics is therefore to question the Maxwellian linear electromagnetism of the 19th century (and its bosons, photons), which remains the current framework of astrophysics.
Dispersion and turbulence in the interstellar medium
The radio signal received from pulsars is a powerful tool for studying the interstellar medium. The frequency signal dispersion (DM) measurement, the observation of multi-propagation and scintillation phenomena, and the measurement of the Faraday rotation of the signal inform us on the electronic content along the line of sight, on the magnetic field in the Galaxy, and on their long-term variations.
The decametric emission of Jupiter is well known since the 1950s, via the Maser-cyclotron interactions with Io and Ganymede. Cyclotron emission, between 20 MHz and a few GHz, is highly variable and its observation has led to important results in plasma physics. This technique also constitutes a possible way of detecting giant extra-solar planets.