Shortest Microlensing Event with a Bound Planet: KMT-2016-BLG-2605

Abstract

KMT-2016-BLG-2605, with planet-host mass ratio q = 0.012 ± 0.001, has the shortest Einstein timescale, t E = 3.41 ± 0.13 days, of any planetary microlensing event to date. This prompts us to examine the full sample of 7 short (t E < 7 day) planetary events with good q measurements. We find that six have clustered Einstein radii θ E = 115 ± 20 µas and lens-source relative proper motions µ rel ≃ 9.5 ± 2.5 mas yr −1 . For the seventh, these two quantities could not be measured. These distributions are consistent with a Galactic-bulge population of very low-mass (VLM) hosts near the hydrogen-burning limit. This conjecture could be verified by imaging at first adaptive-optics light on next-generation (30m) telescopes. Based on a preliminary assessment of the sample, "planetary" companions (i.e., below the deuterium-burning limit) are divided into "genuine planets", formed in their disks by core accretion, and very low-mass brown dwarfs, which form like stars. We discuss techniques for expanding the sample, which include taking account of the peculiar "anomaly dominated" morphology of the KMT-2016-BLG-2605 light curve.

Characterizing microlensing planetary system OGLE-2014-BLG-0676Lb with adaptive optics imaging

“…Several more microlensing super Jupiters around likely M dwarf hosts have been discovered since OGLE-2005-BLG-071Lb. According to the recent study by Ryu et al (2021), some binary-lens short-duration events may be brown dwarfs hosting planets that are sub Jupiters and super Jupiters. Shvartzvald et al (2016) suggested a possible frequency deficit in the super-Jupiter population at q ∼ 10 −2 based on the inferred mass-ratio function, which corresponds to the range of 3 M J < M p < 13 M J assuming a typical primary mass of 0.3M .…”

Characterizing microlensing planetary system OGLE-2014-BLG-0676Lb with adaptive optics imaging*

“…Several more microlensing super Jupiters around likely M dwarf hosts have been discovered since OGLE-2005-BLG-071Lb. According to the recent study by Ryu et al (2021), some binary-lens short-duration events may be brown dwarfs hosting planets that are sub Jupiters and super Jupiters. Shvartzvald et al (2016) suggested a possible frequency deficit in the super-Jupiter population at q ∼ 10 −2 based on the inferred mass-ratio function, which corresponds to the range of 3 M J < M p < 13 M J assuming a typical primary mass of 0.3 M .…”