Microlensing search for extrasolar planets: observational strategy, discoveries and implications

• Published in: Proceedings of the International Astronomical Union Vol. 3; no. S249; pp. 31 - 34
• Main Authors: Cassan, Arnaud, Sumi, Takahiro, Kubas, Daniel
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.10.2007
• Subjects: Astronomy; Contributed Papers; Extrasolar planets; Microlenses; Planet detection; Telescopes; Extrasolar planets; Gravitational microlensing
• ISSN: 1743-9213; 1743-9221
• DOI: 10.1017/S1743921308016323

Microlensing has proven to be a valuable tool to search for extrasolar planets of Jovian- to Super-Earth-mass planets at orbits of a few AU. Since planetary signals are of very short duration, an intense and continuous monitoring is required. This is achieved by ground-based networks of telescopes (PLANET/RoboNET, μFUN) following up targets, which are identified as microlensing events by single dedicated telescopes (OGLE, MOA). Microlensing has led to four already published detections of extrasolar planets, one of them being OGLE 2005-BLG-390Lb, a planet of only ∼5.5 M⊕ orbiting its M-dwarf host star at ∼2.6 AU. Very recent observations (May–September 2007) provided four 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.