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

Abstract

We apply the automated AnomalyFinder algorithm of Paper I (Zang et al. 2021b) to 2018-2019 light curves from the ≃ 13 deg 2 covered by the six KMT-Net prime fields, with cadences Γ ≥ 2 hr −1 . We find a total of 10 planets with mass ratios q < 2 × 10 −4 , including five newly discovered planets, one planet that was reported in Paper I, and recovery of four previously discovered planets. One of the new planets, OGLE-2018-BLG-0977Lb, is in a planetary-caustic event, while the other four (OGLE-2018-BLG-0506Lb, OGLE-2018-BLG-0516Lb, OGLE-2019-BLG-1492Lb, and KMT-2019-BLG-0253) are revealed by a "dip" in the light curve as the source crosses the host-planet axis on the opposite side of the planet. These subtle signals were missed in previous by-eye searches. The planethost separations (scaled to the Einstein radius), s, and planet-host mass ratios, q, are, respectively, (s, q × 10 5 ) = (0.88, 4.1), (0.96 ± 0.10, 8.3), (0.94 ± 0.07, 13), (0.97 ± 0.07, 18), and (0.97 ± 0.04, 4.1), where the "±" indicates a discrete degeneracy. The ten planets are spread out over the range −5 < log q < −3.7. Together with the two planets previously reported with q ∼ 10 −5 from the 2018-2019 non-prime KMT fields, this result suggests that planets toward the bottom of this mass-ratio range may be more common than previously believed.

Mass Production of 2021 KMTNet Microlensing Planets I

“…The third channel is comprised of planets discovered using the KMT AnomalyFinder (Zang et al 2021b), which has so far been applied only to the 13 deg 2 of KMT fields with cadence Γ ≥ 2 hr −1 and only to 2018-2019 data. In fact, only eight of the newly discovered planets from this search have been reported, including seven with mass ratios q ≤ 2 × 10 −4 (Zang et al 2021b;Hwang et al 2021), and one wide-orbit planet (Wang et al 2022). However, there are expected to be many additional new planets when the AnomalyFinder is applied to additional seasons, to lower-cadence fields, and when the q > 2 × 10 −4 planets are thoroughly investigated.…”

“…The most straightforward and secure way to provide these analyses and data is to publish all of these planetary events. The experience of Hwang et al (2021) suggests that of order five planetary events can suitably be grouped in one paper. On the one hand, this allows various "routine" information, such as field position, cadence, source color, etc., to be grouped into tables, rather than expressed as repeated narrative.…”

“…While the first channel (by-eye selection) cannot itself be subjected to rigorous statistical analysis, it serves as an important external check on the AnomalyFinder selection process. For example, Hwang et al (2021) used by-eye detections to identify three planets that were missed by the AnomalyFinder selection. All three "failures" were explained by known effects, i.e., one was below the χ 2 threshold, one was in a binary-star system, and one was "buried" in a high-magnification event with strong finite-source effects at peak.…”

“…Of course, there is substantial overlap between these three channels. For example, Hwang et al (2021) showed that 23 of the 30 planets that they reported were already known, most being already published but with some in preparation. And some planets that are discovered in real time by survey+followup will have sufficient survey data that they will later be rediscovered by the AnomalyFinder search.…”

OGLE-2019-BLG-0468Lb,c: two microlensing giant planets around a G-type star

“…One group of events for this investigation are those with weak anomalies. Investigating such events led to the discoveries of 16 microlensing planets including KMT-2018, KMT-2016-BLG-2364Lb, KMT-2016-BLG-2397Lb, OGLE-2017-BLG-0604Lb, OGLE-2017, KMT-2018-BLG-0748Lb (Han et al 2020d), KMT-2019-BLG-1339Lb (Han et al 2020b, KMT-2018-BLG-1976, KMT-2018-BLG-1996, OGLE-2019, OGLE-2018-BLG-0977Lb, OGLE-2018-BLG-0506Lb, OGLE-2018-BLG-0516Lb, OGLE-2019-BLG-1492Lb, KMT-2019-BLG-0253 (Hwang et al 2021), and OGLE-2019-BLG-1053(Zang et al 2021.…”