Imaging & Spectroscopy

KMT-2021-BLG-2609Lb and KMT-2022-BLG-0303Lb: Microlensing Planets Identified Through Signals Produced By Major-image Perturbations

By Keith Cowing
Status Report
astro-ph.EP
July 26, 2024
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KMT-2021-BLG-2609Lb and KMT-2022-BLG-0303Lb: Microlensing Planets Identified Through Signals Produced By Major-image Perturbations
Variation of lensing caustics induced by planets. We illustrate two sets of caustics with planet-to-host mass ratios q = 2 × 10−3 (depicted in red) and q = 2 × 10−4 (depicted in blue). Within each set, a series of caustics demonstrates variations depending on the planetary separation s. The coordinates are centered at the position of the planet host and the lengths are scaled to the Einstein radius. The dotted circle centered at the origin represents the Einstein ring. — astro-ph.EP

We investigate microlensing data collected by the Korea Microlensing Telescope Network (KMTNet) survey. Our investigation reveals that the light curves of two lensing events, KMT-2021-BLG-2609 and KMT-2022-BLG-0303, exhibit a similar anomaly, in which short-term positive deviations appear on the sides of the low-magnification lensing light curves.

To unravel the nature of these anomalies, we meticulously analyze each of the lensing events. Our investigations reveal that these anomalies stem from a shared channel, wherein the source passed near the planetary caustic induced by a planet with projected separations from the host star exceeding the Einstein radius. We find that interpreting the anomaly of KMT-2021-BLG-2609 is complicated by the “inner–outer” degeneracy, whereas for KMT-2022-BLG-0303, there is no such issue despite similar lens-system configurations.

In addition to this degeneracy, interpreting the anomaly in KMT-2021-BLG-2609 involves an additional degeneracy between a pair of solutions, in which the source partially envelops the caustic and the other three solutions in which the source fully envelopes the caustic. As in an earlier case of this so-called von Schlieffen–Cannae degeneracy, the former solutions have substantially higher mass ratio.

Through Bayesian analyses conducted based on the measured lensing observables of the event time scale and angular Einstein radius, the host of KMT-2021-BLG-2609L is determined to be a low-mass star with a mass ∼0.2 M⊙ in terms of a median posterior value, while the planet’s mass ranges from approximately 0.032 to 0.112 times that of Jupiter, depending on the solutions. For the planetary system KMT-2022-BLG-0303L, it features a planet with a mass of approximately 0.51 MJ and a host star with a mass of about 0.37 M⊙. In both cases, the lenses are most likely situated in the bulge.

Cheongho Han, Michael D. Albrow, Chung-Uk Lee, Sun-Ju Chung, Andrew Gould, Kyu-Ha Hwang, Youn Kil Jung, Chung-Uk Lee, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Jennifer C. Yee, Hongjing Yang, Weicheng Zang, Sang-Mok Cha, Doeon Kim, Dong-Jin Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge

Comments: 10 pages, 11 figures, 6 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2407.17002 [astro-ph.EP] (or arXiv:2407.17002v1 [astro-ph.EP] for this version)
Submission history
From: Cheongho Han
[v1] Wed, 24 Jul 2024 04:49:45 UTC (1,500 KB)
https://arxiv.org/abs/2407.17002

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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