Systematic KMTNet Planetary Anomaly Search. XIII. Complete Sample of 2021 Prime Field Planets

TL;DR

This paper reports on the 2021 KMTNet planetary anomaly search, identifying new planetary systems and candidates, emphasizing the importance of systematic searches for unbiased planet demographic studies.

Contribution

It extends the systematic KMTNet anomaly search series to 2021, discovering additional planets and candidates, and highlights the necessity of systematic methods for complete microlensing planet samples.

Findings

Seven new planetary systems found in 2021 data.

Three additional planet candidates identified.

Systematic search remains crucial alongside by-eye detection.

Abstract

The Systematic KMTNet Planetary Anomaly Search series was conducted using the KMTNet data archived from $2016$ to $2019$. From this first phase of the series, we reported a total of $50$ planetary systems hidden in the data archive, which represent about $35\%$ of the total microlensing planets discovered from $2016$ to $2019$, demonstrating that this semi-machine-based search is a crucial channel for building a complete microlensing planet sample. We continue this series for $2021$ and beyond to expand the microlensing planet sample. In this work for the $2021$ KMTNet high-cadence fields (Prime fields), we find seven hidden planetary systems and three planet candidates. These new planets represent about $33\%$ of the total microlensing planets discovered within the Prime fields observed during the $2021$ bulge season. While the by-eye search is the primary channel for detecting microlensing planets (i.e., two-thirds of microlensing planet discoveries), this work clearly shows that a systematic search series is still necessary for constructing a complete microlensing planet sample. Such a sample is essential for conducting unbiased statistical studies of planet demographics in our Galaxy. Datasets for all the events used for analyses in this work are publicly available.