Three microlensing planets with no caustic-crossing features

Han, Cheongho; Udalski, A.; Kim, Doeon; Lee, Chung-Uk; Albrow, Michael D.; Chung, Sun-Ju; Gould, Andrew; Hwang, Kyu-Ha; Jung, Youn Kil; Ryu, Yoon-Hyun; Shin, In-Gu; Shvartzvald, Yossi; Yee, Jennifer C.; Zang, Weicheng; Cha, Sang-Mok; Kim, Dong-Jin; Lee, Dong-Joo; Lee, Yongseok; Park, Byeong-Gon; Pogge, Richard W.; Mróz, P.; Szymański, M. K.; Skowron, J.; Poleski, R.; Soszyński, I.; Ulaczyk, K.; Rybicki, K.; Iwanek, Patryk; Wrona, Marcin; Gromadzki, M.

doi:10.1051/0004-6361/202140758

“…The anomaly pattern characterized by a dip surrounded by shallow bumps suggests that the anomaly was produced by the source star's passage through the planet-host axis on the opposite side of the planet. Example planetary lensing events with similar anomaly patterns are found in OGLE-2018-BLG-0677 (Herrera-Martín et al 2020), KMT-2018-BLG-1976, KMT-2018-BLG-1996(Han et al 2021a), KMT-2019-BLG-0253, OGLE-2018-BLG-0506, OGLE-2018-BLG-0516, and OGLE-2019-BLG-0149 (Hwang et al 2022). The possibility of a binarysource interpretation (Gaudi 1998;Gaudi & Han 2004) for the origin of the anomaly is excluded because a source companion produces only positive deviations, while the observed anomaly exhibits a negative deviation.…”

Section: Light Curve Analysismentioning

confidence: 72%

KMT-2018-BLG-1988Lb: Microlensing super-Earth orbiting a low-mass disk dwarf

Han

¹

,

Gould

²

,

Albrow

³

et al. 2022

A&A

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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, Mplanet = 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 Mhost = 0.47−0.25+0.33 M⊙ and a distance of DL = 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.

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“…In other events, source stars pass close to the caustic instead of crossing it, e.g., the left event in Figure 3. Some examples of such events are reported in Han et al (2021); Kondo et al (2021).…”

Section: Statistical Calculationsmentioning

confidence: 95%

Sensitivity to habitable planets in the \textit{Roman} microlensing survey

Sajadian

2021

Preprint

0

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We study the Roman sensitivity to exoplanets in the Habitable Zone (HZ). The Roman efficiency for detecting habitable planets is maximized for three classes of planetary microlensing events with close caustic topologies. (a) The events with the lens distances of D l 7 kpc, the host lens masses of M h 0.6M . By assuming Jupiter-mass planets in the HZs, these events have q 0.001 and d 0.17 (q is their mass ratio and d is the projected planet-host distance on the sky plane normalized to the Einstein radius). The events with primary lenses, M h 0.1M , while their lens systems are either (b) close to the observer with D l 1 kpc or (c) close to the Galactic bulge, D l 7 kpc. For Jupiter-mass planets in the HZs of the primary lenses, the events in these two classes have q 0.01, d 0.04. The events in the class (a) make larger caustics. By simulating planetary microlensing events detectable by Roman, we conclude that the Roman efficiencies for detecting Earth-and Jupiter-mass planets in the Optimistic HZs (OHZs, which is the region between [0.5, 2] AU around a Sun-like star) are 0.01% and 5%, respectively. If we assume that one exoplanet orbits each microlens in microlensing events detectable by Roman ( i.e., ∼ 27000 ), this telescope has the potential to detects 35 exoplanets with the projected planet-host distances in the OHZs with only one having a mass 10M ⊕ . According to the simulation, 27 of these exoplanets are actually in the OHZs.

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“…The source of KMT-2018-BLG-1996 is relatively bright, and therefore, the Gaia proper motion can be taken at face value. Han et al (2021a) did not make use of this measured μ S . However, because μ S is that of a typical bulge star, while the light curve does not yield a μ rel measurement, incorporating the μ S measurement would not have significantly affected their Bayesian analysis.…”

Section: Role Of Gaia In Planetary Microlensingmentioning

confidence: 99%

Systematic KMTNet Planetary Anomaly Search. VI. Complete Sample of 2018 Sub-prime-field Planets

Jung

¹

,

Zang

²

,

Han

³

et al. 2022

AJ

Self Cite

19

0

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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%.

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Three microlensing planets with no caustic-crossing features

Cited by 17 publications

References 41 publications

KMT-2018-BLG-1988Lb: Microlensing super-Earth orbiting a low-mass disk dwarf

KMT-2018-BLG-1988Lb: Microlensing super-Earth orbiting a low-mass disk dwarf

Sensitivity to habitable planets in the \textit{Roman} microlensing survey

Systematic KMTNet Planetary Anomaly Search. VI. Complete Sample of 2018 Sub-prime-field Planets

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