A Neptune-mass Free-floating Planet Candidate Discovered by Microlensing
Surveys
release_ngawar5xvrfcxoh5dkfhkt3bcy
by
Przemek Mroz, Y.-H. Ryu, J. Skowron, A. Udalski, A. Gould, M. K.
Szymanski, I. Soszynski, R. Poleski, P. Pietrukowicz, S. Kozlowski, M.
Pawlak, K. Ulaczyk (+17 others)
2017
Abstract
Current microlensing surveys are sensitive to free-floating planets down to
Earth-mass objects. All published microlensing events attributed to unbound
planets were identified based on their short timescale (below two days), but
lacked an angular Einstein radius measurement (and hence lacked a significant
constraint on the lens mass). Here, we present the discovery of a Neptune-mass
free-floating planet candidate in the ultrashort (t_ E=0.320±0.003
days) microlensing event OGLE-2016-BLG-1540. The event exhibited strong
finite-source effects, which allowed us to measure its angular Einstein radius
of θ_ E=9.2±0.5 μas. There remains, however, a degeneracy
between the lens mass and distance. The combination of the source proper motion
and source-lens relative proper motion measurements favors a Neptune-mass lens
located in the Galactic disk. However, we cannot rule out that the lens is a
Saturn-mass object belonging to the bulge population. We exclude stellar
companions up to 15 au.
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1712.01042v1
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