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Exoplanet Seminar



Microlensing at the space era: mass and distance measurement of stars and planets in the Milky Way
Dr. Clément Ranc (GSFC)

ABSTRACT: Gravitational microlensing occupies a unique niche in exoplanet sensitivity with its ability to detect planets down to below an Earth mass, and beyond the snow line. It is the region where planet formation is thought to be most efficient according to the core-accretion theory. After a general introduction on microlensing, I will show how the international coordination between several observing groups allows the detection of exoplanets and brown dwarfs at Galactic distances from the Earth. While the photometric light curve of a microlensing event observed from the ground provides constraints on the lensing system (exoplanetary system, stellar binary or isolated star), in many cases the lens mass and distance from Earth remain degenerate. I will mention several methods currently used to measure the mass of the lens and break this degeneracy, including high resolution techniques, and parallax. In particular, I will speak about the Kepler-2 mission which was dedicated to the observation of microlensing events toward the Galactic Bulge during its campaign 9 (K2C9). Measuring the microlensing parallax from simultaneous space- and ground-based observations yields the measurement of the lens mass and distance for most binary/exoplanetary systems. I will also show how the microlensing parallax alone can be used to build the distance distribution of the isolated stars toward the Bulge. The analysis of the K2C9 observations is still an on-going process, primarily because extracting the microlensing light curves is very challenging. I will show that our new method to extract the K2 data produces precise photometry in crowded stellar fields, such as the K2C9 field. These K2C9 observations provides a unique test for the primary mass-measurement method that will be employed by WFIRST, and that will extend the statistical census of exoplanet to cold exoplanets beyond the snow-line.

Date December 19, 2017
Start/End Time 12:00 PM - 01:00 PM
Location B34, E215
Event Type Seminars/Colloquia
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