We are involved since 2006 in the preparation and support of gamma-ray pulsar observations with the Large Area Telescope (LAT) on board the Fermi satellite. The NRT “high energy” programs represent 1200 hours of telescope time per year, with 270 pulsars monitored regularly, and are coordinated at the international level.
Since the launch of Fermi in 2008, observations of the gamma-ray sky by the Large Area Telescope (LAT) have revealed the pulsations of more than 230 pulsars in the GeV range, of which more than half are due to radio ephemeris. The NRT has contributed significantly, in particular to the discovery of the gamma-ray emission of millisecond pulsars. The temporal and spectral results of the Fermi LAT pulsar observations, completed by multi-wavelength (X and radio) observation campaigns, have allowed to strongly constrain the choice of the pulsar emission models, and thus to refine our understanding of the mechanisms at stake and of the geometry of the emission beams.
NRT, NenuFAR, MeerKAT and neutron star populations surveys
We also use the telescopes of the Nançay station to perform blind surveys for new pulsars. This topic will grow in the coming years with the progressive commissioning of NenuFAR. We plan a focused survey of known pulsars to study the shape of the spectrum at low frequency and the dispersive effects due to the interstellar medium. The combined observations of pulsars with NRT, LOFAR and NenuFAR will allow a detailed study of the shape and duration of the radio pulsation profile as well as its polarization, as a function of frequency, and will allow to estimate the intensity of the magnetic field with altitude, to understand the evolution of the rotation rate and to deduce the geometry of the system. This program will be completed by a blind survey of the whole accessible sky to characterize the local and faint population.
The algorithms to search for new pulsars naturally lead to the detection of fast transient signals, such as the population of Fast Radio Bursts (FRBs). We hope to discover new events and we collaborate with theorists to characterize them. Finally, we are involved in the commissioning and operation of MeerKAT, the precursor of SKA in South Africa, within the consortia TRAPPUM (survey) and MeerTIME (timing).
Finally, the activity of the Fast Radio Burst (FRB) repeater 121102 is followed very regularly since its discovery with the NRT.