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| « Microlensing search for extrasolar planets: Discoveries and implications » |
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Arnaud Cassan |
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Galactic gravitational microlensing has proven to be a valuable tool in the search for Jovian- and super-Earth-mass planets with orbital radii of a few AUs. It is, for now, the only method that opens a window onto this mass/orbit regime. Since planetary signals are of very short duration, an intense and continuous monitoring is required. This is achieved by ground-based networks of telescopes (such as PLANET/RoboNET) following up targets, which are identified as microlensing events by single dedicated telescopes (OGLE and MOA). Microlensing has already led to four published detections of extrasolar planets, one of them being OGLE-2005-BLG-390Lb, a planet of only ~5.5 M_earth orbiting its M-dwarf host star at ~2.6 AU. Very recent observations (March-October 2007) provided more planetary candidates, still under study, that will double the number of detections. For non-planetary microlensing events observed from 1995 to 2006 we compute detection efficiency diagrams, which can then be used to derive an estimate of the Galactic abundance of cool planets in the mass regime from Jupiters to sub-Neptunes.
I will start with a selected history of gravitational lensing and its application to search for exoplanets in the Galaxy, describe the method itself and the current observational setup. Then I will review and comment the main results published so far, present our recent discoveries and discuss the wider implications for extrasolar planetary research. |
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vendredi 11 janvier 2008 - 11:00 Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |