Precise Mass Measurements of Cold Planets Discovered by Microlensing: Cold planet Mass Function and Spatial Distribution in Our Galaxy

• Main Author: Beaulieu, Jean-Philippe
• Other Authors: Institut d'Astrophysique de Paris (IAP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2019
• Subjects: [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP]; Iceland
• Online Access: https://hal.science/hal-02404982

International audience Microlensing is probing the unique population of cold planets down to Earth mass orbiting around any kind of star, at any distance towards the galactic center. Relative physical parameters are known to good precision from the modelling of the light curves, but it is necessary to combine the result of light curve modeling with lens mass-distance relations from additional observations and/or perform a Bayesian analysis with a galactic model. Often, physical parameters are determined to 30-50 %. Recently, two kinds of constraints on masses have been extensively used, coming from ground-space parallax Spitzer observations and high angular resolution observations with adaptive optics or HST. Our team has shown that we can derive physical parameters on known systems to 10 % or better with mass-distance relations obtained from high angular resolution observations, either by detecting the lens flux and/or resolving source and lens and measuring the amplitude and direction of their relative proper motion. This work is also a pathfinder of the mass measurement method to be applied to WFIRST and Euclid microlensing programs. We will report the results from our large observing program with KECK and HST over 40+ planetary systems. We revised the stellar and planetary masses and distances for these systems, and often found significant differences, even despite the initial large error bars. We also show some tensions with the constraint from ground-space parallax Spitzer data, where Spitzer lightcurves photometry seems to be plagued by under estimated systematics for the faint targets in very crowded field. We will discuss the impact of our analysis on the cold planet mass function. With our revised distances, we found that the systems we re-visited so far tend to be located in the Sagittarius or Scuttum-Crux arms, or at the tip of the bar.