mercredi 9 décembre 2015, par Clément Ranc (IAP)
Jeudi 10 décembre 2015 à 11h00 , Lieu : Salle de conférence du bâtiment 17
Gravitational microlensing is a powerful technique to detect extrasolar planets at galactic distances, and holds great promises in detecting populations of brown dwarfs companions to stars. The new generations of alert telescopes have strongly increased the number of detected microlensing events for the last few years and now exceed 2000 per year. Among these events, planet searches routinely yield over 20 detections. The physical properties of the lensing systems are inferred either from the detection of specific physical effects (source size, all kind of parallax measurements etc.), or from additional observations using high angular resolution imaging. Observing microlensing events with an interferometer is a new additional way to break the degeneracies, by resolving the multiple images that are created during an event. Until now, no observation has yet succeeded.
After a description of the main features of gravitational microlensing, I will present a formalism that closely combines interferometric and microlensing observable quantities. From this formalism arise the resulting observable quantities that are naturally constrained through an interferometric observation. Then, I will present an up-to-date analysis of the expected number of targets in the light of new microlensing surveys.
The recent improvements in the sensitivity of long baseline interferometers such as CHARA and VLTI open new perspectives regarding interferometric observations of microlensing events. The observational strategy requires an efficient alert system that shall involve the already existing photometric follow-up of the events. Interferometric microlensing observations carry great promises to characterize completely many more microlensing systems in a near future.