Przemek Mroz, Andrzej Udalski, Jan Skowron, Radoslaw Poleski, Szymon Kozlowski, Michal K. Szymanski, Igor Soszynski, Lukasz Wyrzykowski, Pawel Pietrukowicz, Krzysztof Ulaczyk, Dorota Skowron, Michal Pawlak
(Submitted on 24 Jul 2017)

Gravitational microlensing is the only method capable of exploring the entire population of free-floating planets down to Mars-mass objects, because the microlensing signal does not depend on the brightness of the lensing object. A characteristic timescale of microlensing events depends on the mass of the lens: the less massive the lens, the shorter the microlensing event. A previous analysis of 474 microlensing events found an excess of very short events (1-2 days) – more than known stellar populations would suggest – indicating the existence of a large population of unbound or wide-orbit Jupiter-mass planets (reported to be almost twice as common as main-sequence stars). These results, however, do not match predictions of planet formation theories and are in conflict with surveys of young clusters. Here we report the analysis of a six times larger sample of microlensing events discovered during the years 2010-2015. Although our survey has very high sensitivity (detection efficiency) to short-timescale (1–2 days) microlensing events, we found no excess of events with timescales in this range, with a 95% upper limit on the frequency of Jupiter-mass free-floating or wide-orbit planets of 0.25 planet per main-sequence star. We detected a few possible ultrashort-timescale events (with timescales of less than 0.5 day), which may indicate the existence of Earth- and super-Earth-mass free-floating planets, as predicted by planet-formation theories. [abridged]

Comments:    published in Nature, authors’ version (see nature.com for the published version)
Subjects:    Earth and Planetary Astrophysics (astro-ph.EP)
DOI:    10.1038/nature23276
Cite as:    arXiv:1707.07634 [astro-ph.EP] (or arXiv:1707.07634v1 [astro-ph.EP] for this version)
Submission history
From: Przemek Mroz 
[v1] Mon, 24 Jul 2017 16:25:24 GMT (1117kb,D)
http://xxx.lanl.gov/abs/1707.07634