OGLE-2017-BLG-1049: Another giant planet microlensing event

TL;DR

This paper reports the discovery of a giant exoplanet via microlensing, estimating its properties through Bayesian analysis due to the lack of microlens parallax measurement, and discusses future prospects for direct host star observation.

Contribution

First detailed Bayesian analysis of a microlensing event without parallax to estimate the physical parameters of a giant exoplanet system.

Findings

Host star mass: ~0.55 M_sun

Planet mass: ~5.5 M_Jup

Projected separation: ~3.9 au

Abstract

We report a giant exoplanet discovery in the microlensing event OGLE-2017-BLG-1049, which is a planet-host star mass ratio of $q=9.53\pm0.39\times10^{-3}$ and has a caustic crossing feature in the Korea Microlensing Telescope Network (KMTNet) observations. The caustic crossing feature yields an angular Einstein radius of $\theta_{\rm E}=0.52 \pm 0.11\ {\rm mas}$. However, the microlens parallax is not measured because of the time scale of the event $t_{\rm E}\simeq 29\ {\rm days}$, which is not long enough in this case to determine the microlens parallax. Thus, we perform a Bayesian analysis to estimate physical quantities of the lens system. From this, we find that the lens system has a star with mass $M_{\rm h}=0.55^{+0.36}_{-0.29} \ M_{\odot}$ hosting a giant planet with $M_{\rm p}=5.53^{+3.62}_{-2.87} \ M_{\rm Jup}$, at a distance of $D_{\rm L}=5.67^{+1.11}_{-1.52}\ {\rm kpc}$. The projected star-planet separation in units of the Einstein radius $(\theta_{\rm E})$ corresponding to the total mass of the lens system is $a_{\perp}=3.92^{+1.10}_{-1.32}\ \rm{au}$. This means that the planet is located beyond the snow line of the host. The relative lens-source proper motion is $\mu_{\rm rel}\sim 7 \ \rm{mas \ yr^{-1}}$, thus the lens and source will be separated from each other within 10 years. Then the flux of the host star can be measured by a 30m class telescope with high-resolution imaging in the future, and thus its mass can be determined.