Systematic KMTNet Planetary Anomaly Search, Paper 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 .

Systematic KMTNet Planetary Anomaly Search, Paper II: Six New $q<2\times 10^{-4}$ Mass-ratio Planets

“…Summary of Microlensing Planets q < 10 −4 Years q < 4.3 × 10 −5 q > 4. As reported by Zang et al (2021b), their method recovered the planets in KMT-2019-BLG-0842 (Jung et al 2020b) and OGLE-2019-BLG-0960 (Yee et al 2021), i.e., the two previous low-q planets from 2019. And they also reported the discovery of the lowest mass-ratio planetary-caustic 1 event to date: OGLE-2019-BLG-1053.…”

“…This would be similar to the approach formerly carried out by the Microlensing Follow Up Network (µFUN, Gould et al 2010), but with much more efficient target selection due to continuous KMT coverage. Zang et al (2021b) (Paper I) initiated a third approach: subject the residuals from single-lens single-source (1L1S) fits to the end-of-year-pipeline light curves to a search for "bumps" or "dips" based on a modified version of the KMT EventFinder algorithm (Kim et al 2018a;Gould 1996). At that time, the Zang et al (2021b) approach could only be applied to 2019 data because the 2016-2017 online reductions were not of sufficiently high quality and the 2018 photometry files lacked some auxiliary data needed for this method.…”

“…Zang et al (2021b) (Paper I) initiated a third approach: subject the residuals from single-lens single-source (1L1S) fits to the end-of-year-pipeline light curves to a search for "bumps" or "dips" based on a modified version of the KMT EventFinder algorithm (Kim et al 2018a;Gould 1996). At that time, the Zang et al (2021b) approach could only be applied to 2019 data because the 2016-2017 online reductions were not of sufficiently high quality and the 2018 photometry files lacked some auxiliary data needed for this method. However, the 2018 files have already been updated and work on the 2016-2017 files is in progress.…”

“…Hence, there are good prospects for establishing a large homogeneous sample of q < 10 −4 planets by applying this technique to several years of KMT data. Here, we begin a program of detailed analysis and publication of all q < 2 × 10 −4 planets found from application of the Zang et al (2021b) method. This will enable a systematic study of the planet mass-ratio function in the regime of the hypothesized break.…”

Three faint-source microlensing planets detected via resonant-caustic channel

“…One project has been conducted to find planet-induced anomalies via an automatized algorithm. Hwang et al (2021) applied the automated AnomalyFinder software (Zang et al 2021) to the 2018-2019 lensing light curves from the ∼ 13 deg 2 of sky covered by the six KMTNet prime fields with cadences ≥ 2 hr −1 . From this investigation, they reported 6 newly detected planets with mass ratios q < 2×10 −4 , including OGLE-2019-BLG-1053Lb, KMT-2019-BLG-0253Lb, OGLE-2018-BLG-0506Lb, OGLE-2018-BLG-0516Lb, OGLE-2019-BLG-1492Lb, and OGLE-2018-BLG-0977.…”