Systematic KMTNet Planetary Anomaly Search. I. OGLE-2019-BLG-1053Lb, a Buried Terrestrial Planet

Abstract

In order to exhume the buried signatures of "missing planetary caustics" in the KMTNet data, we conducted a systematic anomaly search to the residuals from point-source point-lens fits, based on a modified version of the KMTNet EventFinder algorithm. This search reveals the lowest mass-ratio planetary caustic to date in the microlensing event OGLE-2019-BLG-1053, for which the planetary signal had not been noticed before. The planetary system has a planet-host mass ratio of q = (1.25±0.13)×10 −5 . A Bayesian analysis yields estimates of the mass of the host star, M host = 0.61 +0.29 −0.24 M , the mass of its planet, M planet = 2.48 +1.19 −0.98 M ⊕ , the projected planet-host separation, a ⊥ = 3.4 +0.5 −0.5 au, and the lens distance of D L = 6.8 +0.6 −0.9 kpc. The discovery of this very low mass-ratio planet illustrates the utility of our method and opens a new window for a large and homogeneous sample to study the microlensing planet-host mass-ratio function down to q ∼ 10 −5 .

OGLE-2014-BLG-0319: A Sub-Jupiter-Mass Planetary Event Encountered Degeneracy with Different Mass Ratios and Lens-Source Relative Proper Motions

“…Gaudi & Gould (1997) also predict such a degeneracy, see their Figure 1. Recently, Zang et al (2021a) also encountered the similar degeneracy in a planetary event with q ∼ 10 −5 and ρ ∼ 10 −3 . A second degeneracy is between models with sources crossing near the caustic and models with large sources crossing over the caustic, i.e.…”

Systematic KMTNet Planetary Anomaly Search, Paper III: One Wide-Orbit Planet And Two Stellar Binaries

“…Because the anomalous feature is either small or well separated from the main peak, the majority of the wide-orbit planets could only be detected via systematic searches for anomalous events. Now with the successful implementation of systematic anomaly search in the KMTNet data (Zang et al 2021), we expect that the sample of wide-orbit planets will expand more rapidly.…”

“…Our Bayesian analysis applies the procedures and the Galactic model of Zang et al (2021). The Galactic model is defined by the mass function of the lens, the stellar number density profile and the dynamical distributions.…”

“…In this work, we report the detections of wide-orbit planets from the Korea Microlensing Telescope Network (KMTNet, Kim et al 2016). The three events reported here were discovered in the KMTNet AnomalyFinder algorithm for planet anomalies (Zang et al 2021) in the 2018 high-cadence events (Γ K ≥ 2 hr −1 , Hwang et al 2021) and first classified as (candidate) planetary events with separations beyond roughly twice the Einstein ring radius, although later detailed modelings revealed that two of them are in fact stellar binaries with close orbits. We describe the observations of the reported events in Section 2, explain our analysis of the microlensing light curves in Section 3, and derive physical parameters of the lens systems in Section 4.…”

“…Planets at such wide separations have long orbital periods and introduce small reflex motions on their hosts, making other methods such as radial velocity very inefficient. So far microlensing has detected over 100 planets, the majority of which have the planet-star projected separation of a factor of two within the Einstein ring radius (see Figure 1 of Zang et al (2021) for an illustration). At even larger separations, the lensing signals due to the planet and its host star are largely decoupled, resulting in a reduced sensitivity to planet detections.…”