Revisiting the microlensing event OGLE 2012-BLG-0026: A solar mass star with two cold giant planets

TL;DR

This study refines the parameters of a microlensing system with a solar-mass star and two cold giant planets using additional data and high-resolution imaging, providing more accurate mass, distance, and potential for future metallicity measurement.

Contribution

The paper presents a revised model of the OGLE-2012-BLG-0026 system with improved host star flux measurements and adaptive optics constraints, enhancing understanding of the star-planet system.

Findings

Host star mass: 1.06 ± 0.05 M_sun

Planets: 0.145 ± 0.008 and 0.86 ± 0.06 M_Jup

System distance: 4.0 ± 0.3 kpc

Abstract

Two cold, gas giant planets orbiting a G-type main sequence star in the galactic disk have previously been discovered in the high magnification microlensing event OGLE-2012-BLG-0026 (Han et al. 2013). Here we present revised host star flux measurements and a refined model for the two-planet system using additional light curve data. We performed high angular resolution adaptive optics imaging with the Keck and Subaru telescopes at two epochs while the source star was still amplified. We detected the lens flux, $H=16.39 \pm 0.08$. The lens, a disk star, is brighter than predicted from the modeling in the original study. We revisited the light curve modeling using additional photometric data from the B\&C telescope in New Zealand and CTIO 1.3m H band light curve. We then include the Keck and Subaru adaptive optic observation constraints. The system is composed of a $\sim 4-9$ Gyr lens star of $\rm M_{lens} = 1.06 \pm 0.05~\,M_\odot$ at a distance of $\rm D_{lens} = 4.0 \pm 0.3~$kpc, orbited by two giant planets of $\rm 0.145 \pm 0.008\ M_{\rm Jup}$ and $0.86 \pm 0.06~\rm M_{\rm Jup}$ with projected separations of $4.0 \pm 0.5 $ AU and $4.8 \pm 0.7$ AU respectively. Since the lens is brighter than the source star by $16 \pm 8 \%$ in H, with no other blend within one arcsec, it will be possible to estimate its metallicity by subsequent IR spectroscopy with 8--10~m class telescopes. By adding a constraint on the metallicity it will be possible to refine the age of the system.