Abstract We present the analysis of seven microlensing planetary events with planet/host mass ratios q < 10 −4 : KMT-2017-BLG-1194, KMT-2017-BLG-0428, KMT-2019-BLG-1806, KMT-2017-BLG-1003, KMT-2019-BLG-1367, OGLE-2017-BLG-1806, and KMT-2016-BLG-1105. They were identified by applying the Korea Microlensing Telescope Network (KMTNet) AnomalyFinder algorithm to 2016–2019 KMTNet events. A Bayesian analysis indicates that all the lens systems consist of a cold super-Earth orbiting an M or K dwarf. Together with 17 previously published and three that will be published elsewhere, AnomalyFinder has found a total of 27 planets that have solutions with q < 10 −4 from 2016–2019 KMTNet events, which lays the foundation for the first statistical analysis of the planetary mass-ratio function based on KMTNet data. By reviewing the 27 planets, we find that the missing planetary caustics problem in the KMTNet planetary sample has been solved by AnomalyFinder. We also find a desert of high-magnification planetary signals ( A ≳ 65), and a follow-up project for KMTNet high-magnification events could detect at least two more q < 10 −4 planets per year and form an independent statistical sample.
more »
« less
Systematic KMTNet planetary anomaly search. IV. Complete sample of 2019 prime-field
We report the complete statistical planetary sample from the prime fields (Γ ≥ 2 h−1) of the 2019 Korea Microlensing Telescope Network (KMTNet) microlensing survey. We develop the optimized KMTNet AnomalyFinder algorithm and apply it to the 2019 KMTNet prime fields. We find a total of 13 homogeneously selected planets and report the analysis of three planetary events, KMT-2019-BLG-(1042,1552,2974). The planet–host mass ratios, q, for the three planetary events are 6.34 × 10−4, 4.89 × 10−3, and 6.18 × 10−4, respectively. A Bayesian analysis indicates the three planets are all cold giant planets beyond the snow line of their host stars. The 13 planets are basically uniform in log q over the range −5.0 < log q < −1.5. This result suggests that the planets below qbreak = 1.7 × 10−4 proposed by the MOA-II survey may be more common than previously believed. This work is an early component of a large project to determine the KMTNet mass-ratio function, and the whole sample of 2016–2019 KMTNet events should contain about 120 planets.
more » « less- Award ID(s):
- 2108414
- NSF-PAR ID:
- 10430602
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 515
- Issue:
- 1
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- p. 928-939
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
ABSTRACT We report the discovery and analysis of a candidate triple-lens single-source (3L1S) microlensing event, OGLE-2019-BLG-1470. This event was first classified as a normal binary-lens single-source (2L1S) event, but a careful 2L1S modelling showed that it needs an additional lens or source to fit the observed data. It is found that the 3L1S model provides the best fit, but the binary-lens binary-source (2L2S) model is only disfavoured by Δχ2 ≃ 18. All of the feasible models include a planet with planet-to-host mass-ratios 10−3 ≲ q ≲ 10−2. A Bayesian analysis based on a Galactic model indicates that the planet is super-Jovian, and the projected host-planet separation is about 3 au. Specifically, for the best-fitting 3L1S model, the two stars have masses of $M_1=0.57^{+0.43}_{-0.32}{\rm M}_{\odot}$, and $M_2=0.18^{+0.15}_{-0.10}\mathrm{M}_{\odot}$ with projected separation of $1.3^{+0.5}_{-0.5}$ au, and the planetary mass is $M_3=2.2^{+1.8}_{-1.3}M_{\rm {Jupiter}}$. For the 2L2S model, the masses of the host star and the planet are $0.55^{+0.44}_{-0.31}\mathrm{M}_{\odot }$ and $4.6^{+3.7}_{-2.6}M_{\rm {Jupiter}}$, respectively. By investigating the properties of all known microlensing planets in binary systems, we find that all planets in binary systems published by the KMTNet survey are located inside the resonant caustics range with q ≳ 2 × 10−3, indicating the incompleteness of the KMTNet sample for planets in binary systems. Thus, planets in binary systems cannot be included in the current study of the KMTNet mass-ratio function, and a systematic search for planetary anomalies in KMTNet microlensing light curves of binary systems is needed.more » « less
-
ABSTRACT We present the observations and analysis of a high-magnification microlensing planetary event, KMT-2022-BLG-0440, for which the weak and short-lived planetary signal was covered by both the KMTNet survey and follow-up observations. The binary-lens models with a central caustic provide the best fits, with a planet/host mass ratio, q = 0.75–1.00 × 10−4 at 1σ. The binary-lens models with a resonant caustic and a brown-dwarf mass ratio are both excluded by Δχ2 > 70. The binary-source model can fit the anomaly well but is rejected by the ‘colour argument’ on the second source. From Bayesian analyses, it is estimated that the host star is likely a K or M dwarf located in the Galactic disc, the planet probably has a Neptune-mass, and the projected planet-host separation is $1.9^{+0.6}_{-0.7}$ or $4.6^{+1.4}_{-1.7}$ au, subject to the close/wide degeneracy. This is the third q < 10−4 planet from a high-magnification planetary signal (A ≳ 65). Together with another such planet, KMT-2021-BLG-0171Lb, the ongoing follow-up program for the KMTNet high-magnification events has demonstrated its ability to detect high-magnification planetary signals for q < 10−4 planets, which are challenging for the current microlensing surveys.more » « less
-
Abstract We complete the analysis of all 2018 sub-prime-field microlensing planets identified by the KMTNet AnomalyFinder. Among the 9 previously unpublished events with clear planetary solutions, 6 are clearly planetary (OGLE-2018-BLG-0298, KMT-2018-BLG-0087, KMT-2018-BLG-0247, KMT-2018-BLG-0030, OGLE-2018-BLG-1119, and KMT-2018-BLG-2602), while the remaining 3 are ambiguous in nature. The above ordering of these events is made to facilitate grouping of their Bayesian estimates: the first two are lower-mass gas giants while the last four are Jovian-class planets; the first three most likely lie in the bulge, the last in the disk, and the remaining two are equally likely to be in either population. More specifically, these six planets have host masses M host = ( 0.69 − 0.30 + 0.34 , 0.10 − 0.05 + 0.14 , 0.29 − 0.14 + 0.28 , 0.51 − 0.31 + 0.43 , 0.48 − 0.28 + 0.35 , 0.66 − 0.36 + 0.42 ) M ⊙ , planet masses M planet = ( 0.14 − 0.06 + 0.07 , 0.23 − 0.12 + 0.32 , 2.11 − 1.04 + 2.09 , 1.45 − 0.88 + 1.23 , 0.91 − 0.52 + 0.66 , 1.15 − 0.63 + 0.73 ) M Jup , and distances D L = ( 6.54 − 1.23 + 0.95 , 7.02 − 1.15 + 1.03 , 6.76 − 1.24 + 0.99 , 6.48 − 1.96 + 1.28 , 5.76 − 2.48 + 1.43 , 4.31 − 1.84 + 1.97 ) kpc . In addition, there are 8 previously published sub-prime-field planets that were selected by the AnomalyFinder algorithm. Together with a companion paper on 2018 prime-field planets, this work lays the basis for comprehensive statistical studies. We carry out two such studies, one on caustic topologies and the other on the role of Gaia data. From the first, as expected, half (17/33) of the 2018 planets likely to enter the mass-ratio analysis have non-caustic-crossing anomalies. However, only 1 of the 5 noncaustic anomalies with planet-host mass ratio q < 10 −3 was discovered by eye (compared to 7 of the 12 with q > 10 −3 ), showing the importance of the semiautomated AnomalyFinder search. From the second, we find that Gaia has played a major role in the interpretation of 16% of the sample and a supplementary role in 6%.more » « less
-
Aims. We reexamine high-magnification microlensing events in the previous data collected by the KMTNet survey with the aim of finding planetary signals that were not noticed before. In this work, we report the planetary system KMT-2018-BLG-1988L, which was found from this investigation. Methods. The planetary signal appears as a deviation with ≲0.2 mag from a single-lens light curve and lasted for about 6 h. The deviation exhibits a pattern of a dip surrounded by weak bumps on both sides of the dip. The analysis of the lensing light curve indicates that the signal is produced by a low-mass-ratio ( q ~ 4 × 10 −5 ) planetary companion located near the Einstein ring of the host star. Results. The mass of the planet, M planet = 6.8 −3.5 +4.7 M ⊕ and 5.6 −2.8 +3.8 M ⊕ for the two possible solutions, estimated from the Bayesian analysis indicates that the planet is in the regime of a super-Earth. The host of the planet is a disk star with a mass of M host = 0.47 −0.25 +0.33 M ⊙ and a distance of D L = 4.2 −.14 +1.8 kpc. KMT-2018-BLG-1988Lb is the 18th known microlensing planet with a mass below the upper limit of a super-Earth. The fact that 15 out of the 18 known microlensing planets with masses ≲10 M ⊕ were detected in the 5 yr following the full operation of the KMTNet survey indicates that the KMTNet database is an important reservoir of very low-mass planets.more » « less
