WFIRST Exoplanet Mass-measurement Method Finds a Planetary Mass of 39 ± 8 M_⊕ for OGLE-2012-BLG-0950Lb

Abstract

We present the analysis of the simultaneous high resolution images from the Hubble Space Telescope and Keck Adaptive Optics system of the planetary event OGLE-2012-BLG-0950 that determine that the system consists of a 0.58 ± 0.04M host star orbited by a 39±8M ⊕ planet of at projected separation of 2.54±0.23 AU. The planetary system is located at a distance of 2.19 ± 0.23 kpc from Earth. This is the second microlens planet beyond the snow line with a mass measured to be in the mass range 20-80M ⊕ . The runaway gas accretion process of the core accretion model predicts few planets in this mass range, because giant planets are thought to be growing rapidly at these masses and they rarely complete growth at this mass. So, this result suggests that the

Kojima-1Lb Is a Mildly Cold Neptune around the Brightest Microlensing Host Star

“…First, the geocentric source-lens relative proper motion is estimated to be m =  25.34 0.44 geo masyr −1 , enabling us to spatially separate the source and lens stars in ∼2 yr from the event using ground-based AO instruments (e.g., Keck/NIRC2) or spacebased telescopes (e.g., Hubble Space Telescope). By resolving the two stars, one can confirm the relative proper motion (including its direction) and the brightness of the host star in an independent way (e.g., Batista et al 2015;Bennett et al 2015;Bhattacharya et al 2018).…”

OGLE-2015-BLG-1649Lb: A Gas Giant Planet around a Low-mass Dwarf

“…Although our Subaru AO observations were carried out when the source star was still magnified, we can yet obtain the source magnitude in the H band directly if additional Subaru observations are conducted in the near future. Considering the high relative proper motion, image elongation could be also measured with high-resolution observations in a few years time (Bhattacharya et al 2018). For these reasons, this planetary microlensing event should be one of the highest priorities for future observation using a highresolution instrument.…”

OGLE-2016-BLG-0156: Microlensing Event with Pronounced Microlens-parallax Effects Yielding a Precise Lens Mass Measurement

“…which is similar to that of the the lens. When the lens brightness is similar to the brightness of the source, the lens and source can be better resolved as demonstrated for events OGLE-2005-BLG-169 (Bennett et al 2015, MOA-2008-BLG-310 (Bhattacharya et al 2017, and OGLE-2012-BLG-0950 (Bhattacharya et al 2018).…”

“…By applying the same criterion, the lens and source of OGLE-2016-BLG-0156 can be resolved if similar follow-up observations are conducted ∼8.4 yr after the event, i.e., after 2024. For the case of another lensing event OGLE-2012-BLG-0950, Bhattacharya et al (2018) resolved the source and lens using Keck and the Hubble Space Telescope when they were separated by ∼34 mas. According to this criterion, then, the source and lens of this event would be resolved in 2022.…”