Showing 1–50 of 304 results for author: Miyazaki, S

Four Giant Planets from 2024 KMTNet Microlensing Campaign

Authors: Cheongho Han, Andrzej Udalski, Ian A. Bond, Chung-Uk Lee, Jiyuan Zhang, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Youn Kil Jung, Kyu-Ha Hwang, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Jennifer C. Yee, Weicheng Zang, Hongjing Yang, Doeon Kim, Dong-Jin Kim, Byeong-Gon Park, Przemek Mróz, Michał K. Szymański, Jan Skowron, Radosław Poleski, Igor Soszyński, Paweł Pietrukowicz , et al. (34 additional authors not shown)

Abstract: In this work, we present analyses of four newly discovered planetary microlensing events from the 2024 KMTNet survey season: KMT-2024-BLG-0176, KMT-2024-BLG-0349, KMT-2024-BLG-1870, and KMT-2024-BLG-2087. In each case, the planetary nature was revealed through distinct types of anomalies in the lensing light curves: a positive bump near the peak for KMT-2024-BLG-0176, an asymmetric peak for KMT-20… ▽ More In this work, we present analyses of four newly discovered planetary microlensing events from the 2024 KMTNet survey season: KMT-2024-BLG-0176, KMT-2024-BLG-0349, KMT-2024-BLG-1870, and KMT-2024-BLG-2087. In each case, the planetary nature was revealed through distinct types of anomalies in the lensing light curves: a positive bump near the peak for KMT-2024-BLG-0176, an asymmetric peak for KMT-2024-BLG-0349, a short-duration central dip for KMT-2024-BLG-1870, and a caustic-crossing feature for KMT-2024-BLG-2087. Detailed modeling of the light curves confirms that these anomalies are produced by planetary companions with planet-to-host mass ratios in the range of $(1.5\text{--}17.9)\times 10^{-3}$. Despite the diversity of signal morphologies, all planets detected in these events are giant planets with masses comparable to or exceeding that of Jupiter in the Solar System. Each planet orbits a host star less massive than the Sun, emphasizing the strength of microlensing in uncovering planetary systems around low-mass stellar hosts. △ Less

Submitted 10 December, 2025; originally announced December 2025.

Comments: 13 pages, 7 tables, 7 figures

The eROSITA Final Equatorial-Depth Survey (eFEDS): X-ray stacking analysis of Subaru's optically selected clusters spanning low richness regime

Authors: N. T. Nguyen-Dang, N. Ota, N. Okabe, M. Oguri, I. Mitsuishi, T. H. Reiprich, F. Pacaud, E. Bulbul, J. S. Sanders, M. Brüggen, A. Liu, Y. Tsujita, I. Chiu, V. Ghirardini, S. Grandis, M. Klein, K. Migkas, H. Miyatake, S. Miyazaki, M. E. Ramos-Ceja

Abstract: This is the second paper in a series exploring the X-ray properties of galaxy clusters optically selected by the Subaru Hyper Suprime-Cam (HSC) survey, using data from the SRG/eROSITA Final Equatorial-Depth Survey (eFEDS). We aim to investigate scaling relations between observable cluster properties and mass, and to study the radial X-ray profiles of a large sample of optically selected clusters.… ▽ More This is the second paper in a series exploring the X-ray properties of galaxy clusters optically selected by the Subaru Hyper Suprime-Cam (HSC) survey, using data from the SRG/eROSITA Final Equatorial-Depth Survey (eFEDS). We aim to investigate scaling relations between observable cluster properties and mass, and to study the radial X-ray profiles of a large sample of optically selected clusters. We analyze a sample of 997 CAMIRA clusters with richness $N > 15$ and redshifts of $0.1 < z < 1.3$. Using bolometric luminosities derived from count rates and a weak-lensing mass calibration, we study the $L-M$ and $N-M$ scaling relations through stacking analysis, while accounting for selection effects and redshift evolution. We also compare clusters with and without X-ray counterparts in the eFEDS catalog in terms of their scaling relations and surface brightness profiles. The best-fit $L-M$ slope ($1.56^{+0.14}_{-0.12}$) is slightly steeper than the self-similar prediction, yet remains consistent with our previous findings. The $N-M$ slope ($0.766^{+0.070}_{-0.060}$) broadly agrees with theoretical expectations and other optical samples. The data do not require any additional redshift evolution beyond the standard self-similar scaling, although current constraints on evolution remain weak. X-ray detected clusters exhibit a steeper $L-M$ slope, higher central surface brightness, and more centrally concentrated X-ray profiles than undetected systems. Our results highlight systematic differences in the X-ray properties between optically and X-ray selected cluster samples. This study extends scaling relation analyses into lower mass and luminosity regimes, demonstrating the value of combining deep X-ray and optical surveys like eROSITA and Subaru HSC. △ Less

Submitted 5 December, 2025; originally announced December 2025.

Comments: 17 pages, 11 figures, submitted to A&A

Historic microlensing events in the euclid Galactic Bulge Survey

Authors: V. Bozza, L. Salmeri, P. Rota, E. Bachelet, J. -P. Beaulieu, A. A. Cole, J. C. Cuillandre, E. Kerins, I. Mcdonald, P. Mróz, M. Penny, C. Ranc, N. Rektsini, E. Thygesen, H. Verma, A. Udalski, R. Poleski, J. Skowron, M. K. Szymański, I. Soszyński, P. Pietrukowicz, S. Kozłowski, K. Ulaczyk, K. A. Rybicki, P. Iwanek , et al. (25 additional authors not shown)

Abstract: Microlensing campaigns have a long history of observations covering the Galactic bulge, where thousands of detections have been obtained, including many exoplanetary systems. The Euclid Galactic Bulge Survey represents a unique opportunity to revisit a large number of past events and attempt the lens-source resolution of known events falling in the covered area. As the analysis of individual event… ▽ More Microlensing campaigns have a long history of observations covering the Galactic bulge, where thousands of detections have been obtained, including many exoplanetary systems. The Euclid Galactic Bulge Survey represents a unique opportunity to revisit a large number of past events and attempt the lens-source resolution of known events falling in the covered area. As the analysis of individual events requires non-negligible efforts, it is important to establish priorities among all possible targets, identifying those candidates with the higher chance for a successful resolution of the lens from the source and with the highest scientific interest. Drawing from the databases of the three main microlensing surveys (OGLE, MOA and KMTNet), we compile the complete catalog of past microlensing events in the Euclid survey footprint up to year 2023, containing 8081 entries. By re-modeling all events and cross-checking with Galactic models, we estimate the relative lens-source proper motions for all events. Taking into account all uncertainties, for each microlensing event we are able to estimate the probability that the lens is separated from the source by more than a given angular distance threshold. Hence, we rank all events by their resolution probability, providing additional useful information that will guide future analyses on the most promising candidates. A particular attention is dedicated to known planetary microlensing events. △ Less

Submitted 5 November, 2025; originally announced November 2025.

Comments: 12 pages, 12 figures

Six binary brown dwarf candidates identified by microlensing

Authors: Cheongho Han, Chung-Uk Lee, Ian A. Bond, Andrzej Udalski, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Youn Kil Jung, Kyu-Ha Hwang, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Jennifer C. Yee, Weicheng Zang, Hongjing Yang, Sang-Mok Cha, Doeon Kim, Dong-Jin Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz, Michał K. Szymański , et al. (35 additional authors not shown)

Abstract: In this study, we analyze microlensing events from the 2023 and 2024 observing seasons to identify cases likely caused by binary systems composed of BDs. By applying criteria that the binary-lens events exhibit well-resolved caustics, short time scales ($t_{\rm E} \lesssim 9$ days), and have small angular Einstein radii ($θ_{\rm E} \lesssim 0.17$~mas), we identify six candidate binary BD events: M… ▽ More In this study, we analyze microlensing events from the 2023 and 2024 observing seasons to identify cases likely caused by binary systems composed of BDs. By applying criteria that the binary-lens events exhibit well-resolved caustics, short time scales ($t_{\rm E} \lesssim 9$ days), and have small angular Einstein radii ($θ_{\rm E} \lesssim 0.17$~mas), we identify six candidate binary BD events: MOA-2023-BLG-331, KMT-2023-BLG-2019, KMT-2024-BLG-1005, KMT-2024-BLG-1518, MOA-2024-BLG-181, and KMT-2024-BLG-2486. Analysis of these events leads to models that provide precise estimates for both lensing observables, $t_{\rm E}$ and $θ_{\rm E}$. We estimate the masses of the binary components through Bayesian analysis, utilizing the constraints from $t_{\rm E}$ and $θ_{\rm E}$. The results show that for the events KMT-2024-BLG-1005, KMT-2024-BLG-1518, MOA-2024-BLG-181, and KMT-2024-BLG-2486, the probability that both binary components lie within the BD mass range exceeds 50\%, indicating a high likelihood that the lenses of these events are binary BDs. In contrast, for MOA-2023-BLG-331L and KMT-2023-BLG-2019L, the probabilities that the lower-mass components of the binary lenses lie within the BD mass range exceed 50\%, while the probabilities for the heavier components are below 50\%, suggesting that these systems are more likely to consist of a low-mass M dwarf and a BD. The brown-dwarf nature of the binary candidates can ultimately be confirmed by combining the measured lens-source relative proper motions with high-resolution imaging taken at a later time. △ Less

Submitted 27 October, 2025; originally announced October 2025.

Comments: 11 pages, 9 figures

Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. IV. Lens Mass and Distance Measurements

Authors: Sean K. Terry, Etienne Bachelet, Farzaneh Zohrabi, Himanshu Verma, Alison Crisp, Macy Huston, Carissma McGee, Matthew Penny, Natasha S. Abrams, Michael D. Albrow, Jay Anderson, Fatemeh Bagheri, Jean-Phillipe Beaulieu, Andrea Bellini, David P. Bennett, Galen Bergsten, T. Dex Bhadra, Aparna Bhattacharya, Ian A. Bond, Valerio Bozza, Christopher Brandon, Sebastiano Calchi Novati, Sean Carey, Jessie Christiansen, William DeRocco , et al. (32 additional authors not shown)

Abstract: As part of the Galactic Bulge Time Domain Survey (GBTDS), the Nancy Grace Roman Galactic Exoplanet Survey (RGES) will use microlensing to discover cold outer planets and free-floating planets unbound to stars. NASA has established several science requirements for the GBTDS to ensure RGES success. A key advantage of RGES is Roman's high angular resolution, which will allow detection of flux from ma… ▽ More As part of the Galactic Bulge Time Domain Survey (GBTDS), the Nancy Grace Roman Galactic Exoplanet Survey (RGES) will use microlensing to discover cold outer planets and free-floating planets unbound to stars. NASA has established several science requirements for the GBTDS to ensure RGES success. A key advantage of RGES is Roman's high angular resolution, which will allow detection of flux from many host stars. One requirement specifies that Roman must measure the masses and distances of 40% of detected planet hosts with 20% precision or better. To test this, we simulated microlensing events toward the GBTDS fields and used Fisher matrix analysis to estimate light curve parameter uncertainties. Combining these with Roman imaging observables (lens flux, relative lens-source proper motion), we estimated the achievable precision of lens mass and distance measurements. Using pyLIMASS, a publicly available code for estimating lens properties, we applied this analysis to 3,000 simulated events. Assuming the Cassan et al. (2012) exoplanet mass function, we find that >40% of host stars meet the required 20% precision threshold, confirming that the GBTDS can satisfy the mission requirement. We validated our approach by comparing our inferred lens masses and distances to empirical measurements from detailed image-constrained light curve modeling of historical microlensing events with Hubble and Keck follow-up imaging. Our results agree within roughly 1 sigma, demonstrating that both approaches yield consistent and reliable mass and distance estimates, and confirming the robustness of our simulations for Roman-era microlensing science. △ Less

Submitted 24 October, 2025; v1 submitted 15 October, 2025; originally announced October 2025.

Comments: Updated. 29 pages, 8 figures, 6 tables, submitted to AJ

microJAX: A Differentiable Framework for Microlensing Modeling with GPU-Accelerated Image-Centered Ray Shooting

Authors: Shota Miyazaki, Hajime Kawahara

Abstract: We introduce microJAX, the first fully differentiable implementation of the image-centered ray-shooting (ICRS) algorithm for gravitational microlensing. Built on JAX and its XLA just-in-time compiler, microJAX exploits GPU parallelism while providing exact gradients through automatic differentiation. The current release supports binary- and triple-lens geometries, including limb-darkened extended-… ▽ More We introduce microJAX, the first fully differentiable implementation of the image-centered ray-shooting (ICRS) algorithm for gravitational microlensing. Built on JAX and its XLA just-in-time compiler, microJAX exploits GPU parallelism while providing exact gradients through automatic differentiation. The current release supports binary- and triple-lens geometries, including limb-darkened extended-source effects, and delivers magnifications that remain differentiable for all model parameters. Benchmarks show that microJAX matches the accuracy of established packages and attains up to a factor of $\sim$5-6 speed-up in the small-source, limb-darkened regime on an NVIDIA A100 GPU. Since the model is fully differentiable, it integrates seamlessly with probabilistic programming frameworks, enabling scalable Hamiltonian Monte Carlo and variational inference workflows. Although the present work focuses on standard microlensing magnification models, the modular architecture is designed to support upcoming implementations of microlensing higher-order effects, while remaining compatible with external likelihood frameworks that incorporate advanced noise models. microJAX thus provides a robust foundation for precise and large-scale surveys anticipated in the coming decade, including the Nancy Grace Roman Space Telescope, where scalable, physically self-consistent inference will be essential for maximizing scientific return. △ Less

Submitted 2 October, 2025; originally announced October 2025.

Comments: 19 pages, 9 figures, 2 tables, Accepted for publication in The Astrophysical Journal

A Comprehensive Analysis of Three Microlensing Planet Candidates with the Planet/Binary Degeneracy

Authors: Jiyuan Zhang, Weicheng Zang, Yoon-Hyun Ryu, Takahiro Sumi, Andrzej Udalski, Shude Mao, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Cheongho Han, Kyu-Ha Hwang, Youn Kil Jung, In-Gu Shin, Yossi Shvartzvald, Jennifer C. Yee, Hongjing Yang, Sang-Mok Cha, Dong-Jin Kim, Seung-Lee Kim, Chung-Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Yunyi Tang , et al. (43 additional authors not shown)

Abstract: We present observations and analyses of three high-magnification microlensing events: KMT-2022-BLG-0954, KMT-2024-BLG-0697, and MOA-2024-BLG-018. All three exhibit the "Planet/Binary" degeneracy, with planetary solutions corresponding to mass ratios in the range $-3.7 < \log q < -2.2$, while the binary solutions yield $\log q > -2.0$. For KMT-2022-BLG-0954, we identify a previously unrecognized de… ▽ More We present observations and analyses of three high-magnification microlensing events: KMT-2022-BLG-0954, KMT-2024-BLG-0697, and MOA-2024-BLG-018. All three exhibit the "Planet/Binary" degeneracy, with planetary solutions corresponding to mass ratios in the range $-3.7 < \log q < -2.2$, while the binary solutions yield $\log q > -2.0$. For KMT-2022-BLG-0954, we identify a previously unrecognized degeneracy among planetary solutions, involving different mass ratios and normalized source radii. In all three cases, single-lens binary-source models are excluded. Bayesian analyses suggest that the planetary solutions correspond to gas giants orbiting M/K dwarfs beyond the snow line, while KMT-2022-BLG-0954 also admits an alternative interpretation as a super-Earth orbiting a late-type M dwarf. The binary solutions imply a diverse set of systems, including M-dwarf pairs and M-dwarf--brown-dwarf binaries. A review of known events subject to the "Planet/Binary" degeneracy shows that in most cases the degeneracy cannot be resolved through follow-up high-resolution imaging, particularly in the presence of the newly identified degeneracy. △ Less

Submitted 22 September, 2025; originally announced September 2025.

Comments: submitted to MNRAS

Six microlensing planets detected via sub-day signals during the 2023 -- 2024 season

Authors: Cheongho Han, Chung-Uk Lee, Andrzej Udalski, Ian A. Bond, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Youn Kil Jung, Kyu-Ha Hwang, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Jennifer C. Yee, Weicheng Zang, Hongjing Yang, Sang-Mok Cha, Doeon Kim, Dong-Jin Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz, Michał K. Szymański , et al. (36 additional authors not shown)

Abstract: We present analyses of six microlensing events: KMT-2023-BLG-0548, KMT-2023-BLG-0830, KMT-2023-BLG-0949, KMT-2024-BLG-1281, KMT-2024-BLG-2059, and KMT-2024-BLG-2242. These were identified in KMTNet data from the 2023 -- 2024 seasons, selected for exhibiting anomalies shorter than one day -- potential signatures of low-mass planetary companions. Detailed modeling of the light curves reveals that th… ▽ More We present analyses of six microlensing events: KMT-2023-BLG-0548, KMT-2023-BLG-0830, KMT-2023-BLG-0949, KMT-2024-BLG-1281, KMT-2024-BLG-2059, and KMT-2024-BLG-2242. These were identified in KMTNet data from the 2023 -- 2024 seasons, selected for exhibiting anomalies shorter than one day -- potential signatures of low-mass planetary companions. Detailed modeling of the light curves reveals that the anomalies in all six events are caused by planetary companions to the lenses. The brief durations of the anomalies are attributed to various factors: a low planet-to-host mass ratio (KMT-2024-BLG-2059, KMT-2024-BLG-2242), a wide planet-host separation (KMT-2023-BLG-0548), small and elongated caustics restricting the source's interaction region (KMT-2023-BLG-0830, KMT-2024-BLG-1281), and a partial caustic crossing (KMT-2023-BLG-0949). { For KMT-2023-BLG-0548, the Bayesian posterior distribution of the lens mass shows two distinct peaks: a low-mass solution indicating a sub-Jovian planet orbiting an M dwarf in the Galactic disk, and a high-mass solution suggesting a super-Jovian planet around a K-type dwarf in the bulge. KMT-2023-BLG-0830 hosts a Neptune-mass planet orbiting an M dwarf in the Galactic bulge. KMT-2023-BLG-0949 involves a super-Jovian planet orbiting a $\sim 0.5~M_\odot$ host located at $\sim 6$ kpc. KMT-2024-BLG-2059Lb is a super-Earth with a mass about seven times that of Earth, orbiting an early M dwarf of $\sim 0.5~M_\odot$. KMT-2024-BLG-1281L hosts a planet slightly more massive than Neptune, orbiting an M dwarf of $\sim 0.3~M_\odot$. The short timescale and small angular Einstein radius of KMT-2024-BLG-2242 suggest a $\sim 0.07~M_\odot$ primary, likely a brown dwarf, with a Uranus/Neptune-mass planet. △ Less

Submitted 5 September, 2025; originally announced September 2025.

Comments: 9 figures, 9 tables

The Prime Focus Infrared Microlensing Experiment (PRIME): First Results

Authors: Takahiro Sumi, David A. H. Buckley, Alexander S. Kutyrev, Motohide Tamura, David P. Bennett, Ian A. Bond, Giuseppe Cataldo, Joseph M. Durbak, S. Bradley Cenko, Dale Fixsen, Orion Guiffreda, Ryusei Hamada, Yuki Hirao, Asahi Idei, Dan Kelly, Markus Loose, Gennadiy N. Lotkin, Eric I. Lyness, Stephen Maher, Shuma Makida, Noriyuki Matsunaga, Shota Miyazaki, Gregory Mosby, Samuel H. Moseley, Tutumi Nagai , et al. (15 additional authors not shown)

Abstract: We present the description of the instruments and the first results of the PRime-focus Infrared Microlensing Experiment (PRIME). PRIME is the first dedicated near-infrared (NIR) microlensing survey telescope located at the South African Astronomical Observatory (SAAO) in Sutherland, South Africa. Among its class, it offers one of the widest fields of view in the NIR regime. PRIME's main goals are… ▽ More We present the description of the instruments and the first results of the PRime-focus Infrared Microlensing Experiment (PRIME). PRIME is the first dedicated near-infrared (NIR) microlensing survey telescope located at the South African Astronomical Observatory (SAAO) in Sutherland, South Africa. Among its class, it offers one of the widest fields of view in the NIR regime. PRIME's main goals are (1) To study planetary formation by measuring the frequency and mass function of planets. In particular, we compare results from the central Galactic bulge (GB), accessible only in the NIR by PRIME, with those from the outer GB by optical surveys. (2) To conduct concurrent observations with NASA's Nancy Grace Roman Space telescope. Due to the different lines of sight between the ground and space, we detect slight variations in light curves, known as ``Space-based parallax." This effect allows us to measure the mass of lens systems and their distance from the Earth. It is the only method to measure the mass of the free-floating planets down to Earth-mass. We began the GB survey in February 2024 and analyzed images through June 1, 2025, identifying 486 microlensing candidates and over a thousand variable stars, including Mira variables, which are useful to study the Galactic structure. We issue real-time alerts for follow-up observations, supporting exoplanet searches, and the chemical evolution studies in the GB. During the off-bulge season, we conduct an all-sky grid survey and Target of Opportunity (ToO) observations of transients, including gravitational wave events, gamma-ray bursts, and other science. △ Less

Submitted 26 November, 2025; v1 submitted 20 August, 2025; originally announced August 2025.

Comments: 16 pages, 15 figures, published in the Astronomical Journal

Journal ref: Sumi et al 2025 AJ 170 338

Four binary microlenses with directly measured masses

Authors: Cheongho Han, Andrzej Udalski, Chung-Uk Lee, Ian A. Bond, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Youn Kil Jung, Kyu-Ha Hwang, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Jennifer C. Yee, Weicheng Zang, Hongjing Yang, Sang-Mok Cha, Doeon Kim, Dong-Jin Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz, Michał K. Szymański , et al. (36 additional authors not shown)

Abstract: We investigated binary lens events from the 2022-2024 microlensing surveys, aiming to identify events suitable for lens mass measurements. We focused on two key light curve features: distinct caustic spikes with resolved crossings for measuring the angular Einstein radius ($θ_{\rm E}$), and long durations enabling microlens-parallax ($π_{\rm E}$) measurements. Four events met these criteria: KMT-2… ▽ More We investigated binary lens events from the 2022-2024 microlensing surveys, aiming to identify events suitable for lens mass measurements. We focused on two key light curve features: distinct caustic spikes with resolved crossings for measuring the angular Einstein radius ($θ_{\rm E}$), and long durations enabling microlens-parallax ($π_{\rm E}$) measurements. Four events met these criteria: KMT-2022-BLG-1479, KMT-2023-BLG-0932, OGLE-2024-BLG-0142, and KMT-2024-BLG-1309. We estimated the angular Einstein radius by combining the normalized source radius measured from modeling the resolved caustic spikes with the angular source radius derived from the source color and magnitude. Additionally, we determined the microlens parallax through light curve modeling, considering higher-order effects caused by the orbital motions of Earth and the binary lens. With measurements of the event timescale, angular Einstein radius, and microlens parallax, we uniquely determined the mass and distance of the lens. For the events KMT-2022-BLG-1479, KMT-2023-BLG-0932, and KMT-2024-BLG-1309, both components of the binary lens have masses lower than that of the Sun, consistent with M-type dwarfs, which are the most common type of lenses in Galactic microlensing events. These lenses are relatively nearby, with distances $\lesssim 2.5$ kpc, indicating their location within the Galactic disk. In contrast, for OGLE-2024-BLG-0142, the primary lens component has a mass similar to that of the Sun, while the companion lens component has about half the mass of the primary. This lens system is situated at a greater distance, roughly 4.5 kpc. △ Less

Submitted 14 August, 2025; originally announced August 2025.

Comments: 11 pages, 9 figures

A Common Origin of Normal Type Ia Supernovae Suggested by the Photometric Diversity

Authors: Weiyu Wu, Ji-an Jiang, Dezheng Meng, Zelin Xu, Keiichi Maeda, Mamoru Doi, Ken'ichi Nomoto, Naoki Yasuda, Masaomi Tanaka, Toshikazu Shigeyama, Nozomu Tominaga, Željko Ivezić, Peter Yoachim, Saurabh W. Jha, Tinggui Wang, Nao Suzuki, Hisanori Furusawa, Andrew J. Connolly, Satoshi Miyazaki

Abstract: In recent years, with an increasing number of type Ia supernovae (SNe Ia) discovered soon after their explosions, a non-negligible fraction of SNe Ia with early-excess emissions (EExSNe Ia) have been confirmed. In this letter, we present a total of \textbf{67} early-phase normal SNe Ia from published papers and ongoing transient survey projects to systematically investigate their photometric behav… ▽ More In recent years, with an increasing number of type Ia supernovae (SNe Ia) discovered soon after their explosions, a non-negligible fraction of SNe Ia with early-excess emissions (EExSNe Ia) have been confirmed. In this letter, we present a total of \textbf{67} early-phase normal SNe Ia from published papers and ongoing transient survey projects to systematically investigate their photometric behaviors from very early time. We found that EExSNe Ia in our sample have longer rise and brighter peak luminosities compared to those of non-EExSNe Ia. Moreover, EExSNe Ia commonly have ``red-bump" features in the early $B-V$ color while non-EExSNe Ia show blueward evolution from the very beginning. Here, we propose that the thin-helium double-detonation scenario can phenomenologically explain the photometric diversities of normal SNe Ia considering different white dwarf-He-shell mass combinations and the viewing-angle effect, implying a unified explosion mechanism of normal-type SNe Ia. To further testify the possible common origin of normal SNe Ia, systematical studies of multiband photometric and spectral properties of early-phase SNe Ia through the new generation wide-field time-domain survey facilities and global real-time follow-up networks are highly demanded. △ Less

Submitted 21 July, 2025; originally announced July 2025.

Comments: 17 pages, 6 figures, and 1 table, accepted for publication in ApJ

KMT-2022-BLG-0086: Another binary-lens binary-source microlensing event

Authors: Sun-Ju Chung, Kyu-Ha Hwang, Jennifer C. Yee, Andrew Gould, Ian A. Bond, Hongjing Yang, Michael D. Albrow, Youn Kil Jung, Cheongho Han, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Weicheng Zang, Sang-Mok Cha, Dong-Jin Kim, Seung-Lee Kim, Chung-Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Fumio Abe, David P. Bennett, Aparna Bhattacharya, Akihiko Fukui , et al. (18 additional authors not shown)

Abstract: We present the analysis of a microlensing event KMT-2022-BLG-0086 of which the overall light curve is not described by a binary-lens single-source (2L1S) model, which suggests the existence of an extra lens or an extra source. We found that the event is best explained by the binary-lens binary-source (2L2S) model, but the 2L2S model is only favored over the triple-lens single-source (3L1S) model b… ▽ More We present the analysis of a microlensing event KMT-2022-BLG-0086 of which the overall light curve is not described by a binary-lens single-source (2L1S) model, which suggests the existence of an extra lens or an extra source. We found that the event is best explained by the binary-lens binary-source (2L2S) model, but the 2L2S model is only favored over the triple-lens single-source (3L1S) model by $Δχ^{2} \simeq 9$. Although the event has noticeable anomalies around the peak of the light curve, they are not enough covered to constrain the angular Einstein radius $θ_{\rm E}$, thus we only measure the minimum angular Einstein radius $θ_{\rm E,min}$. From the Bayesian analysis, it is found that that the binary lens system is a binary star with masses of $(m_1,m_2)=(0.46^{+0.35}_{-0.25}\, M_\odot, 0.75^{+0.67}_{-0.55}\, M_\odot)$ at a distance of $D_{\rm L}=5.87^{+1.21}_{-1.79}$ kpc, while the triple lens system is a brown dwarf or a massive giant planet in a low-mass binary-star system with masses of $(m_1,m_2,m_3)=(0.43^{+0.41}_{-0.35}\, M_\odot, 0.056^{+0.055}_{-0.047}\, M_\odot, 20.84^{+20.20}_{-17.04}\, M_{\rm J})$ at a distance of $D_{\rm L}=4.06^{+1.39}_{-3.28}$ kpc, indicating a disk lens system. The 2L2S model yields the relative lens-source proper motion of $μ_{\rm rel} \geqslant 4.6\, \rm mas\, yr^{-1}$ that is consistent with the Bayesian result, whereas the 3L1S model yields $μ_{\rm rel} \geqslant 18.9\, \rm mas\, yr^{-1}$, which is more than three times larger than that of a typical disk object of $\sim 6\, \rm mas\, yr^{-1}$ and thus is not consistent with the Bayesian result. This suggests that the event is likely caused by the binary-lens binary-source model. △ Less

Submitted 25 June, 2025; originally announced June 2025.

Comments: 13 pages, 10 figures, AJ in press

MOA-2022-BLG-091Lb and KMT-2024-BLG-1209Lb: Microlensing planets detected through weak caustic-crossing signals

Authors: Cheongho Han, Chung-Uk Lee, Andrzej Udalski, Ian A. Bond, Hongjing Yang, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Youn Kil Jung, Kyu-Ha Hwang, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Jennifer C. Yee, Weicheng Zang, Tanagodchaporn Inyanya, Sang-Mok Cha, Doeon Kim, Dong-Jin Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz , et al. (44 additional authors not shown)

Abstract: The light curves of the microlensing events MOA-2022-BLG-091 and KMT-2024-BLG-1209 exhibit anomalies with very similar features. These anomalies appear near the peaks of the light curves, where the magnifications are moderately high, and are distinguished by weak caustic-crossing features with minimal distortion while the source remains inside the caustic. To achieve a deeper understanding of thes… ▽ More The light curves of the microlensing events MOA-2022-BLG-091 and KMT-2024-BLG-1209 exhibit anomalies with very similar features. These anomalies appear near the peaks of the light curves, where the magnifications are moderately high, and are distinguished by weak caustic-crossing features with minimal distortion while the source remains inside the caustic. To achieve a deeper understanding of these anomalies, we conducted a comprehensive analysis of the lensing events. We carried out binary-lens modeling with a thorough exploration of the parameter space. This analysis revealed that the anomalies in both events are of planetary origin, although their exact interpretation is complicated by different types of degeneracy. In the case of MOA-2022-BLG-091, the main difficulty in the interpretation of the anomaly arises from a newly identified degeneracy related to the uncertain angle at which the source trajectory intersects the planet-host axis. For KMT-2024-BLG-1209, the interpretation is affected by the previously known inner-outer degeneracy, which leads to ambiguity between solutions in which the source passes through either the inner or outer caustic region relative to the planet host. Bayesian analysis indicates that the planets in both lens systems are giant planets with masses about 2 to 4 times that of Jupiter, orbiting early K-type main-sequence stars. Both systems are likely located in the Galactic disk at a distance of around 4 kiloparsecs. The degeneracy in KMT-2024-BLG-1209 is challenging to resolve because it stems from intrinsic similarities in the caustic structures of the degenerate solutions. In contrast, the degeneracy in MOA-2022-BLG-091, which occurs by chance rather than from inherent characteristics, is expected to be resolved by the future space based Roman RGES microlensing survey. △ Less

Submitted 28 May, 2025; originally announced May 2025.

Comments: 9 pages, 10 figures

KMT-2022-BLG-1818Lb,c: A Cold Super-Jupiter with a Saturn Sibling

Authors: Hongyu Li, Jiyuan Zhang, Cheongho Han, Weicheng Zang, Youn Kil Jung, Andrzej Udalski, Takahiro Sumi, Hongjing Yang, Renkun Kuang, Shude Mao, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Kyu-Ha Hwang, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Jennifer C. Yee, Sang-Mok Cha, Dong-Jin Kim, Seung-Lee Kim, Chung-Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park , et al. (50 additional authors not shown)

Abstract: We present the discovery and analysis of the sixth microlensing two-planet system, KMT-2022-BLG-1818Lb,c, detected by a follow-up program targeting high-magnification events. Both planets are subject to the well-known ''Close/Wide'' degeneracy, although for the first planet, which has a super-Jovian mass ratio of $q_2 \simeq 5\times 10^{-3}$ in both solutions, the Close topology, with a normalized… ▽ More We present the discovery and analysis of the sixth microlensing two-planet system, KMT-2022-BLG-1818Lb,c, detected by a follow-up program targeting high-magnification events. Both planets are subject to the well-known ''Close/Wide'' degeneracy, although for the first planet, which has a super-Jovian mass ratio of $q_2 \simeq 5\times 10^{-3}$ in both solutions, the Close topology, with a normalized separation of $s\simeq 0.70$, is clearly preferred by $Δχ^2=26$. However, contrary to all previous two-planet microlensing systems, the mass ratio for the second planet, $q_3$, is substantially (factor of $\sim 10$) different for the Close and Wide topologies of the first planet. While this degeneracy is resolved in the present case due to high-cadence follow-up observations, the appearance of this new degeneracy indicates the need for caution in the analysis of future two-planet systems. A Bayesian analysis suggests that the host is likely a K-dwarf star in the Galactic disk. The first planet is probably a super-Jupiter on a Jupiter-like orbit, while the second planet is a Saturn-class planet on either a Mercury-like or Saturn-like orbit. △ Less

Submitted 11 May, 2025; v1 submitted 8 May, 2025; originally announced May 2025.

Comments: submitted to ApJL

Microlensing events indicate that super-Earth exoplanets are common in Jupiter-like orbits

Authors: Weicheng Zang, Youn Kil Jung, Jennifer C. Yee, Kyu-Ha Hwang, Hongjing Yang, Andrzej Udalski, Takahiro Sumi, Andrew Gould, Shude Mao, Michael D. Albrow, Sun-Ju Chung, Cheongho Han, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Sang-Mok Cha, Dong-Jin Kim, Hyoun-Woo Kim, Seung-Lee Kim, Chung-Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Xiangyu Zhang , et al. (43 additional authors not shown)

Abstract: Exoplanets classified as super-Earths are commonly observed on short period orbits, close to their host stars, but their abundance on wider orbits is poorly constrained. Gravitational microlensing is sensitive to exoplanets on wide orbits. We observed the microlensing event OGLE-2016-BLG-0007, which indicates an exoplanet with a planet-to-star mass ratio roughly double the Earth-Sun mass-ratio, on… ▽ More Exoplanets classified as super-Earths are commonly observed on short period orbits, close to their host stars, but their abundance on wider orbits is poorly constrained. Gravitational microlensing is sensitive to exoplanets on wide orbits. We observed the microlensing event OGLE-2016-BLG-0007, which indicates an exoplanet with a planet-to-star mass ratio roughly double the Earth-Sun mass-ratio, on an orbit longer than Saturn's. We combine this event with a larger sample from a microlensing survey to determine the distribution of mass ratios for planets on wide orbits. We infer there are $\sim 0.35$ super-Earth planets per star on Jupiter-like orbits. The observations are most consistent with a bimodal distribution, with separate peaks for super-Earths and gas giants. We suggest that this reflects differences in their formation processes. △ Less

Submitted 28 April, 2025; originally announced April 2025.

Comments: Published in Science

Journal ref: 2025, Science, Vol 388, Issue 6745, pp. 400-404

LGR: LLM-Guided Ranking of Frontiers for Object Goal Navigation

Authors: Mitsuaki Uno, Kanji Tanaka, Daiki Iwata, Yudai Noda, Shoya Miyazaki, Kouki Terashima

Abstract: Object Goal Navigation (OGN) is a fundamental task for robots and AI, with key applications such as mobile robot image databases (MRID). In particular, mapless OGN is essential in scenarios involving unknown or dynamic environments. This study aims to enhance recent modular mapless OGN systems by leveraging the commonsense reasoning capabilities of large language models (LLMs). Specifically, we ad… ▽ More Object Goal Navigation (OGN) is a fundamental task for robots and AI, with key applications such as mobile robot image databases (MRID). In particular, mapless OGN is essential in scenarios involving unknown or dynamic environments. This study aims to enhance recent modular mapless OGN systems by leveraging the commonsense reasoning capabilities of large language models (LLMs). Specifically, we address the challenge of determining the visiting order in frontier-based exploration by framing it as a frontier ranking problem. Our approach is grounded in recent findings that, while LLMs cannot determine the absolute value of a frontier, they excel at evaluating the relative value between multiple frontiers viewed within a single image using the view image as context. We dynamically manage the frontier list by adding and removing elements, using an LLM as a ranking model. The ranking results are represented as reciprocal rank vectors, which are ideal for multi-view, multi-query information fusion. We validate the effectiveness of our method through evaluations in Habitat-Sim. △ Less

Submitted 26 March, 2025; originally announced March 2025.

Comments: 10 pages, 11 figures, technical report

Systematic Reanalysis of KMTNet Microlensing Events, Paper II: Two New Planets in Giant-Source Events

Authors: Hongjing Yang, Jennifer C. Yee, Jiyuan Zhang, Chung-Uk Lee, Dong-Jin Kim, Ian A. Bond, Andrzej Udalski, Kyu-Ha Hwang, Weicheng Zang, Qiyue Qian, Andrew Gould, Shude Mao, Michael D. Albrow, Sun-Ju Chung, Cheongho Han, Youn Kil Jung, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Sang-Mok Cha, Hyoun-Woo Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park , et al. (39 additional authors not shown)

Abstract: In this work, we continue to apply the updated KMTNet tender-love care (TLC) photometric pipeline to historical microlensing events. We apply the pipeline to a subsample of events from the KMTNet database, which we refer to as the giant source sample. Leveraging the improved photometric data, we conduct a systematic search for anomalies within this sample. The search successfully uncovers four new… ▽ More In this work, we continue to apply the updated KMTNet tender-love care (TLC) photometric pipeline to historical microlensing events. We apply the pipeline to a subsample of events from the KMTNet database, which we refer to as the giant source sample. Leveraging the improved photometric data, we conduct a systematic search for anomalies within this sample. The search successfully uncovers four new planet-like anomalies and recovers two previously known planetary signals. After detailed analysis, two of the newly discovered anomalies are confirmed as clear planets: KMT-2019-BLG-0578 and KMT-2021-BLG-0736. Their planet-to-host mass ratios are $q\sim4\times10^{-3}$ and $q\sim1\times10^{-4}$, respectively. Another event, OGLE-2018-BLG-0421 (KMT-2018-BLG-0831), remains ambiguous. Both a stellar companion and a giant planet in the lens system could potentially explain the observed anomaly. The anomaly signal of the last event, MOA-2022-BLG-038 (KMT-2022-BLG-2342), is attributed to an extra source star. Within this sample, our procedure doubles the number of confirmed planets, demonstrating a significant enhancement in the survey sensitivity. △ Less

Submitted 25 April, 2025; v1 submitted 25 March, 2025; originally announced March 2025.

Comments: Author's edition. Accepted for publication in The Astronomical Journal

Analyses of anomalous lensing events detected from the UKIRT microlensing survey

Authors: Cheongho Han, Weicheng Zang, Andrzej Udalski, Chung-Uk Lee, Ian A. Bond, Yongxin Wen, Bo Ma, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Kyu-Ha Hwang, Youn Kil Jung, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Hongjing Yang, Jennifer C. Yee, Doeon Kim, Dong-Jin Kim, Sang-Mok Cha, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge , et al. (39 additional authors not shown)

Abstract: The United Kingdom Infrared Telescope (UKIRT) microlensing survey was conducted over four years, from 2016 to 2019, with the goal of serving as a precursor to future near-infrared microlensing surveys (Shvartzvald et al. 2017). Focusing on stars in the Galactic center and utilizing near-infrared passbands, the survey identified approximately one thousand microlensing events, 27 of which displayed… ▽ More The United Kingdom Infrared Telescope (UKIRT) microlensing survey was conducted over four years, from 2016 to 2019, with the goal of serving as a precursor to future near-infrared microlensing surveys (Shvartzvald et al. 2017). Focusing on stars in the Galactic center and utilizing near-infrared passbands, the survey identified approximately one thousand microlensing events, 27 of which displayed anomalies in their light curves (Wen et al. 2023). This paper presents an analysis of these anomalous events, aiming to uncover the underlying causes of the observed anomalies. The events were analyzed under various configurations, considering the potential binarity of both the lens and the source. For 11 events that were additionally observed by other optical microlensing surveys, including those conducted by the OGLE, KMTNet, and MOA collaborations, we incorporated their data into our analysis. Among the reported anomalous events, we revealed the nature of 24 events except for three events, in which one was likely to be a transient variable, and two were were difficult to accurately characterize their nature due to the limitations of the available data. We confirmed the binary lens nature of the anomalies in 22 events. Among these, we verified the earlier discovery that the companion in the binary lens system UKIRT11L is a planetary object. Accurately describing the anomaly in UKIRT21 required a model that accounted for the binarity of both the lens and the source. For two events UKIRT01 and UKIRT17, the anomalies could be interpreted using either a binary-source or a binary-lens model. △ Less

Submitted 18 March, 2025; originally announced March 2025.

Comments: 17 pages, 26 figures

UNIONS: The Ultraviolet Near-Infrared Optical Northern Survey

Authors: Stephen Gwyn, Alan W. McConnachie, Jean-Charles Cuillandre, Ken C. Chambers, Eugene A. Magnier, Michael J. Hudson, Masamune Oguri, Hisanori Furusawa, Hendrik Hildebrandt, Raymond Carlberg, Sara L. Ellison, Junko Furusawa, Raphaël Gavazzi, Rodrigo Ibata, Yannick Mellier, Ken Osato, H. Aussel, Lucie Baumont, Manuel Bayer, Olivier Boulade, Patrick Côté, David Chemaly, Cail Daley, Pierre-Alain Duc, A. Ellien , et al. (64 additional authors not shown)

Abstract: The Ultraviolet Near-Infrared Optical Northern Survey (UNIONS) is a "collaboration of collaborations" that is using the Canada-France-Hawai'i Telescope, the Pan-STARRS telescopes, and the Subaru Observatory to obtain $ugriz$ images of a core survey region of 6250 deg$^2$ of the northern sky. The $10σ$ point source depth of the data, as measured within a 2-arcsecond diameter aperture, are… ▽ More The Ultraviolet Near-Infrared Optical Northern Survey (UNIONS) is a "collaboration of collaborations" that is using the Canada-France-Hawai'i Telescope, the Pan-STARRS telescopes, and the Subaru Observatory to obtain $ugriz$ images of a core survey region of 6250 deg$^2$ of the northern sky. The $10σ$ point source depth of the data, as measured within a 2-arcsecond diameter aperture, are $[u,g,r,i,z] = [23.7, 24.5, 24.2, 23.8, 23.3]$\ in AB magnitudes. UNIONS is addressing some of the most fundamental questions in astronomy, including the properties of dark matter, the growth of structure in the Universe from the very smallest galaxies to large-scale structure, and the assembly of the Milky Way. It is set to become the major ground-based legacy survey for the northern hemisphere for the next decade and provides an essential northern complement to the static-sky science of the Vera C. Rubin Observatory's Legacy Survey of Space and Time. UNIONS supports the core science mission of the {\it Euclid} space mission by providing the data necessary in the northern hemisphere for the calibration of the wavelength dependence of the {\it Euclid} point-spread function and derivation of photometric redshifts in the North Galactic Cap. This region contains the highest quality sky for {\it Euclid}, with low backgrounds from the zodiacal light, stellar density, extinction, and emission from Galactic cirrus. Here, we describe the UNIONS survey components, science goals, data products, and the current status of the overall program. △ Less

Submitted 17 March, 2025; originally announced March 2025.

Comments: submitted to AJ

Constraints on Ultra-light Axion Dark Matter through Galaxy Cluster Number Counts

Authors: S. Zelmer, E. Artis, E. Bulbul, S. Grandis, V. Ghirardini, A. von der Linden, Y. E. Bahar, F. Balzer, M. Brüggen, I. Chiu, N. Clerc, J. Comparat, F. Kleinebreil, M. Kluge, S. Krippendorf, A. Liu, N. Malavasi, A. Merloni, H. Miyatake, S. Miyazaki, K. Nandra, N. Okabe, M. E. Ramos-Ceja, J. S. Sanders, T. Schrabback , et al. (3 additional authors not shown)

Abstract: Ultra-light axions are hypothetical scalar particles that influence the evolution of large-scale structures of the Universe. Depending on their mass, they can potentially be part of the dark matter component of the Universe, as candidates commonly referred to as fuzzy dark matter. While strong constraints have been established for pure fuzzy dark matter models, the more general scenario where ultr… ▽ More Ultra-light axions are hypothetical scalar particles that influence the evolution of large-scale structures of the Universe. Depending on their mass, they can potentially be part of the dark matter component of the Universe, as candidates commonly referred to as fuzzy dark matter. While strong constraints have been established for pure fuzzy dark matter models, the more general scenario where ultra-light axions constitute only a fraction of the dark matter has been limited to a few observational probes. In this work, we use the galaxy cluster number counts obtained from the first All-Sky Survey (eRASS1) of the SRG/eROSITA mission together with gravitational weak lensing data from the Dark Energy Survey, the Kilo-Degree Survey, and the Hyper Suprime-Cam, to constrain the fraction of ultra-light axions in the mass range $10^{-32}$ eV to $10^{-24}$ eV. We put upper bounds on the ultra-light axion relic density in independent logarithmic axion mass bins by performing a full cosmological parameter inference. We find an exclusion region in the intermediate ultra-light axion mass regime with the tightest bounds reported so far in the mass bins around $m_\mathrm{a}=10^{-27}$ eV with $Ω_\mathrm{a} < 0.0036$ and $m_\mathrm{a}=10^{-26}$ eV with $Ω_\mathrm{a} < 0.0084$, both at 95% confidence level. When combining with CMB probes, these bounds are tightened to $Ω_\mathrm{a} < 0.0030$ in the $m_\mathrm{a}=10^{27}$ eV mass bin and $Ω_\mathrm{a} < 0.0058$ in the $m_\mathrm{a}=10^{-26}$ eV mass bin, both at 95% confidence level. This is the first time that constraints on ultra-light axions have been obtained using the growth of structure measured by galaxy cluster number counts. These results pave the way for large surveys, which can be utilized to obtain tight constraints on the mass and relic density of ultra-light axions with better theoretical modeling of the abundance of halos. △ Less

Submitted 5 February, 2025; originally announced February 2025.

Comments: 16 pages, 11 figures, submitted to A&A

MOA-2022-BLG-033Lb, KMT-2023-BLG-0119Lb, and KMT-2023-BLG-1896Lb: Three low mass-ratio microlensing planets detected through dip signals

Authors: Cheongho Han, Ian A. Bond, Youn Kil Jung, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Kyu-Ha Hwang, 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, Fumio Abe, Richard Barry, David P. Bennett , et al. (23 additional authors not shown)

Abstract: We examined the anomalies in the light curves of the lensing events MOA-2022-BLG-033, KMT-2023-BLG-0119, and KMT-2023-BLG-1896. We conducted detailed modeling of the light curves to uncover the nature of the anomalies. This modeling revealed that all signals originated from planetary companions to the primary lens. The planet-to-host mass ratios are very low: $q\sim 7.5\times 10^{-5}$ for MOA-2022… ▽ More We examined the anomalies in the light curves of the lensing events MOA-2022-BLG-033, KMT-2023-BLG-0119, and KMT-2023-BLG-1896. We conducted detailed modeling of the light curves to uncover the nature of the anomalies. This modeling revealed that all signals originated from planetary companions to the primary lens. The planet-to-host mass ratios are very low: $q\sim 7.5\times 10^{-5}$ for MOA-2022-BLG-033, $q\sim 3.6\times 10^{-4}$ for KMT-2023-BLG-0119, and $q\sim 6.9\times 10^{-5}$ for KMT-2023-BLG-1896. The anomalies occurred as the source passed through the negative deviation region behind the central caustic along the planet-host axis. The solutions are subject to a common inner-outer degeneracy, resulting in variations in estimating the projected planet-host separation. For KMT-2023-BLG-1896, although the planetary scenario provides the best explanation of the anomaly, the binary companion scenario is marginally possible. We estimate the physical parameters of the planetary systems through Bayesian analyses based on the lensing observables. The analysis identifies MOA-2022-BLG-033L as a planetary system with an ice giant, approximately 12 times the mass of Earth, orbiting an early M dwarf star. The companion of KMT-2023-BLG-1896L is also an ice giant, with a mass around 16 Earth masses, orbiting a mid-K-type main-sequence star. The companion of KMT-2023-BLG-0119L, which has a mass about the mass of Saturn, orbits a mid-K-type dwarf star. The lens for MOA-2022-BLG-033 is highly likely to be located in the disk, whereas for the other events, the probabilities of the lens being in the disk or the bulge are roughly comparable. △ Less

Submitted 4 January, 2025; originally announced January 2025.

Comments: 9 pages, 10 figures, 6 tables

ON as ALC: Active Loop Closing Object Goal Navigation

Authors: Daiki Iwata, Kanji Tanaka, Shoya Miyazaki, Kouki Terashima

Abstract: In simultaneous localization and mapping, active loop closing (ALC) is an active vision problem that aims to visually guide a robot to maximize the chances of revisiting previously visited points, thereby resetting the drift errors accumulated in the incrementally built map during travel. However, current mainstream navigation strategies that leverage such incomplete maps as workspace prior knowle… ▽ More In simultaneous localization and mapping, active loop closing (ALC) is an active vision problem that aims to visually guide a robot to maximize the chances of revisiting previously visited points, thereby resetting the drift errors accumulated in the incrementally built map during travel. However, current mainstream navigation strategies that leverage such incomplete maps as workspace prior knowledge often fail in modern long-term autonomy long-distance travel scenarios where map accumulation errors become significant. To address these limitations of map-based navigation, this paper is the first to explore mapless navigation in the embodied AI field, in particular, to utilize object-goal navigation (commonly abbreviated as ON, ObjNav, or OGN) techniques that efficiently explore target objects without using such a prior map. Specifically, in this work, we start from an off-the-shelf mapless ON planner, extend it to utilize a prior map, and further show that the performance in long-distance ALC (LD-ALC) can be maximized by minimizing ``ALC loss" and ``ON loss". This study highlights a simple and effective approach, called ALC-ON (ALCON), to accelerate the progress of challenging long-distance ALC technology by leveraging the growing frontier-guided, data-driven, and LLM-guided ON technologies. △ Less

Submitted 14 May, 2025; v1 submitted 16 December, 2024; originally announced December 2024.

Comments: Draft version of a conference paper with 7 pages, 5 figures, and 1 table

OGLE-2015-BLG-1609Lb: Sub-jovian planet orbiting a low-mass stellar or brown dwarf host

Authors: M. J. Mróz, R. Poleski, A. Udalski, T. Sumi, Y. Tsapras, M. Hundertmark, P. Pietrukowicz, M. K. Szymański, J. Skowron, P. Mróz, M. Gromadzki, P. Iwanek, S. Kozłowski, M. Ratajczak, K. A. Rybicki, D. M. Skowron, I. Soszyński, K. Ulaczyk, M. Wrona, F. Abe, K. Bando, D. P. Bennett, A. Bhattacharya, I. A. Bond, A. Fukui , et al. (48 additional authors not shown)

Abstract: We present a comprehensive analysis of a planetary microlensing event OGLE-2015-BLG-1609. The planetary anomaly was detected by two survey telescopes, OGLE and MOA. Each of these surveys collected enough data over the planetary anomaly to allow for an unambiguous planet detection. Such survey detections of planetary anomalies are needed to build a robust sample of planets that could improve studie… ▽ More We present a comprehensive analysis of a planetary microlensing event OGLE-2015-BLG-1609. The planetary anomaly was detected by two survey telescopes, OGLE and MOA. Each of these surveys collected enough data over the planetary anomaly to allow for an unambiguous planet detection. Such survey detections of planetary anomalies are needed to build a robust sample of planets that could improve studies on the microlensing planetary occurrence rate by reducing biases and statistical uncertainties. In this work, we examined different methods for modeling microlensing events using individual datasets, particularly we incorporated a Galactic model prior to better constrain poorly defined microlensing parallax. Ultimately, we fitted a comprehensive model to all available data, identifying three potential typologies, with two showing comparably high Bayesian evidence. Our analysis indicates that the host of the planet is a brown dwarf with a probability of 34%, or a low-mass stellar object (M-dwarf) with the probability of 66%. △ Less

Submitted 16 December, 2024; v1 submitted 12 December, 2024; originally announced December 2024.

Comments: 12 pages, 7 figures

Journal ref: A&A 698, A126 (2025)

Computational Complexity of Envy-free and Exchange-stable Seat Arrangement Problems on Grid Graphs

Authors: Sota Kawase, Shuichi Miyazaki

Abstract: The Seat Arrangement Problem is a problem of finding a desirable seat arrangement for given preferences of agents and a seat graph that represents a configuration of seats. In this paper, we consider decision problems of determining if an envy-free arrangement exists and an exchange-stable arrangement exists, when a seat graph is an $\ell \times m$ grid graph. When $\ell=1$, the seat graph is a pa… ▽ More The Seat Arrangement Problem is a problem of finding a desirable seat arrangement for given preferences of agents and a seat graph that represents a configuration of seats. In this paper, we consider decision problems of determining if an envy-free arrangement exists and an exchange-stable arrangement exists, when a seat graph is an $\ell \times m$ grid graph. When $\ell=1$, the seat graph is a path of length $m$ and both problems have been known to be NP-complete. In this paper, we extend it and show that both problems are NP-complete for any integer $\ell \geq 2$. △ Less

Submitted 13 January, 2025; v1 submitted 16 November, 2024; originally announced November 2024.

Comments: Typos and errors are corrected

KMT-2021-BLG-0284, KMT-2022-BLG-2480, and KMT-2024-BLG-0412: Three microlensing events involving two lens masses and two source stars

Authors: Cheongho Han, Andrzej Udalski, Ian A. Bond, Chung-Uk Lee, Andrew Gould, Michael D. Albrow, Sun-Ju Chung, Kyu-Ha Hwang, Youn Kil Jung, 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, Przemek Mróz, Michał K. Szymański , et al. (37 additional authors not shown)

Abstract: We carried out a project involving the systematic analysis of microlensing data from the Korea Microlensing Telescope Network survey. The aim of this project is to identify lensing events with complex anomaly features that are difficult to explain using standard binary-lens or binary-source models. Our investigation reveals that the light curves of microlensing events KMT-2021-BLG-0284, KMT-2022-B… ▽ More We carried out a project involving the systematic analysis of microlensing data from the Korea Microlensing Telescope Network survey. The aim of this project is to identify lensing events with complex anomaly features that are difficult to explain using standard binary-lens or binary-source models. Our investigation reveals that the light curves of microlensing events KMT-2021-BLG-0284, KMT-2022-BLG-2480, and KMT-2024-BLG-0412 display highly complex patterns with three or more anomaly features. These features cannot be adequately explained by a binary-lens (2L1S) model alone. However, the 2L1S model can effectively describe certain segments of the light curve. By incorporating an additional source into the modeling, we identified a comprehensive model that accounts for all the observed anomaly features. Bayesian analysis, based on constraints provided by lensing observables, indicates that the lenses of KMT-2021-BLG-0284 and KMT-2024-BLG-0412 are binary systems composed of M dwarfs. For KMT-2022-BLG-2480, the primary lens is an early K-type main-sequence star with an M dwarf companion. The lenses of KMT-2021-BLG-0284 and KMT-2024-BLG-0412 are likely located in the bulge, whereas the lens of KMT-2022-BLG-2480 is more likely situated in the disk. In all events, the binary stars of the sources have similar magnitudes due to a detection bias favoring binary source events with a relatively bright secondary source star, which increases detection efficiency. △ Less

Submitted 13 November, 2024; originally announced November 2024.

Comments: 9 pages, 9 figures

The Microlensing Event Rate and Optical Depth from MOA-II 9 year Survey toward the Galactic Bulge

Authors: Kansuke Nunota, Takahiro Sumi, Naoki Koshimoto, Nicholas J. Rattenbury, Fumio Abe, Richard Barry, David P. Bennett, Aparna Bhattacharya, Akihiko Fukui, Ryusei Hamada, Shunya Hamada, Naoto Hamasaki, Yuki Hirao, Stela Ishitani Silva, Yoshitaka Itow, Yutaka Matsubara, Shota Miyazaki, Yasushi Muraki, Tsutsumi Nagai, Greg Olmschenk, Clement Ranc, Yuki K. Satoh, Daisuke Suzuki, Paul J. Tristram, Aikaterini Vandorou , et al. (1 additional authors not shown)

Abstract: We present measurements of the microlensing optical depth and event rate toward the Galactic bulge using the dataset from the 2006--2014 MOA-II survey, which covers 22 bulge fields spanning ~42 deg^2 between -5 deg < l < 10 deg and -7 deg < b < -1 deg. In the central region with |l|<5 deg, we estimate an optical depth of τ = [1.75+-0.04]*10^-6exp[(0.34+-0.02)(3 deg-|b|)] and an event rate of Γ = [… ▽ More We present measurements of the microlensing optical depth and event rate toward the Galactic bulge using the dataset from the 2006--2014 MOA-II survey, which covers 22 bulge fields spanning ~42 deg^2 between -5 deg < l < 10 deg and -7 deg < b < -1 deg. In the central region with |l|<5 deg, we estimate an optical depth of τ = [1.75+-0.04]*10^-6exp[(0.34+-0.02)(3 deg-|b|)] and an event rate of Γ = [16.08+-0.28]*10^-6exp[(0.44+-0.02)(3 deg-|b|)] star^-1 year^-1 using a sample consisting of 3525 microlensing events, with Einstein radius crossing times of tE < 760 days and source star magnitude of IsWe confirm our results are consistent with the latest measurements from OGLE-IV 8 year dataset (Mróz et al. 2019). We find our result is inconsistent with a prediction based on Galactic models, especially in the central region with |b|<3 deg. These results can be used to improve the Galactic bulge model, and more central regions can be further elucidated by future microlensing experiments, such as The PRime-focus Infrared Microlensing Experiment (PRIME) and Nancy Grace Roman Space Telescope. △ Less

Submitted 30 October, 2024; originally announced October 2024.

The SRG/eROSITA All-Sky Survey : Constraints on the structure growth from cluster number counts

Authors: E. Artis, E. Bulbul, S. Grandis, V. Ghirardini, N. Clerc, R. Seppi, J. Comparat, M. Cataneo, A. von der Linden, Y. E. Bahar, F. Balzer, I. Chiu, D. Gruen, F. Kleinebreil, M. Kluge, S. Krippendorf, X. Li, A. Liu, N. Malavasi, A. Merloni, H. Miyatake, S. Miyazaki, K. Nandra, N. Okabe, F. Pacaud , et al. (7 additional authors not shown)

Abstract: Beyond testing the current cosmological paradigm, cluster number counts can also be utilized to investigate the discrepancies currently affecting current cosmological measurements. In particular, cosmological studies based on cosmic shear and other large-scale structure probes routinely find a value of the amplitude of the fluctuations in the universe S8 smaller than the one inferred from the prim… ▽ More Beyond testing the current cosmological paradigm, cluster number counts can also be utilized to investigate the discrepancies currently affecting current cosmological measurements. In particular, cosmological studies based on cosmic shear and other large-scale structure probes routinely find a value of the amplitude of the fluctuations in the universe S8 smaller than the one inferred from the primary cosmic microwave background. In this work, we investigate this tension by measuring structure evolution across cosmic time as probed by the number counts of the massive halos with the first SRG/eROSITA All-Sky Survey cluster catalog in the Western Galactic Hemisphere complemented with the overlapping Dark Energy Survey Year-3, KiloDegree Survey, and Hyper Suprime-Cam data for weak lensing mass calibration, by implementing two different parameterizations and a model-agnostic method. In the first model, we measure the cosmic linear growth index as γ = 1.19 \pm 0.21, in tension with the standard value of γ = 0.55, but in good statistical agreement with other large-scale structures probes. The second model is a phenomenological scenario in which we rescale the linear matter power spectrum at low redshift to investigate a potential reduction of structure formation, providing similar results. Finally, in a third strategy, we consider a standard ΛCDM cosmology, but we separate the cluster catalog into five redshift bins, measuring the cosmological parameters in each and inferring the evolution of the structure formation, finding hints of a reduction. Interestingly, the S8 value inferred from eRASS1 cluster number counts, when we add a degree of freedom to the matter power spectrum, recovers the value inferred by cosmic shear studies. △ Less

Submitted 12 October, 2024; originally announced October 2024.

Journal ref: A&A 696, A5 (2025)

Peaks in weak lensing mass maps for cluster astrophysics and cosmology

Authors: Masamune Oguri, Satoshi Miyazaki

Abstract: Clusters of galaxies can be identified from peaks in weak lensing aperture mass maps constructed from weak lensing shear catalogs. Such purely gravitational cluster selection considerably differs from traditional cluster selections based on baryonic properties of clusters. In this review, we present the basics and applications of weak lensing shear-selected cluster samples. Detailed studies of bar… ▽ More Clusters of galaxies can be identified from peaks in weak lensing aperture mass maps constructed from weak lensing shear catalogs. Such purely gravitational cluster selection considerably differs from traditional cluster selections based on baryonic properties of clusters. In this review, we present the basics and applications of weak lensing shear-selected cluster samples. Detailed studies of baryonic properties of shear-selected clusters shed new light on cluster astrophysics. The purely gravitational selection suggests that the selection function can be quantified more easily and robustly, which is crucial for deriving accurate cosmological constraints from the abundance of shear-selected clusters. The recent advance of shear-selected cluster studies is driven by the Subaru Hyper Suprime-Cam survey, in which more than 300 shear-selected clusters with the signal-to-noise ration greater than 5 are identified. It is argued that various systematic effects in the cosmological analysis can be mitigated by carefully choosing the set-up of the analysis, including the choice of the kernel functions and the source galaxy sample. △ Less

Submitted 17 December, 2024; v1 submitted 18 September, 2024; originally announced September 2024.

Comments: 13 pages, 3 figures, a review accepted for publication in Proc. Jpn. Acad., Ser. B

Microlensing brown-dwarf companions in binaries detected during the 2022 and 2023 seasons

Authors: Cheongho Han, Ian A. Bond, Andrzej Udalski, Chung-Uk Lee, Andrew Gould, Michael D. Albrow, Sun-Ju Chung, Kyu-Ha Hwang, Youn Kil Jung, 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, Fumio Abe, Ken Bando , et al. (41 additional authors not shown)

Abstract: Building on previous works to construct a homogeneous sample of brown dwarfs in binary systems, we investigate microlensing events detected by the Korea Microlensing Telescope Network (KMTNet) survey during the 2022 and 2023 seasons. Given the difficulty in distinguishing brown-dwarf events from those produced by binary lenses with nearly equal-mass components, we analyze all lensing events detect… ▽ More Building on previous works to construct a homogeneous sample of brown dwarfs in binary systems, we investigate microlensing events detected by the Korea Microlensing Telescope Network (KMTNet) survey during the 2022 and 2023 seasons. Given the difficulty in distinguishing brown-dwarf events from those produced by binary lenses with nearly equal-mass components, we analyze all lensing events detected during the seasons that exhibit anomalies characteristic of binary-lens systems. Using the same criteria consistently applied in previous studies, we identify six additional brown dwarf candidates through the analysis of lensing events KMT-2022-BLG-0412, KMT-2022-BLG-2286, KMT-2023-BLG-0201, KMT-2023-BLG-0601, KMT-2023-BLG-1684, and KMT-2023-BLG-1743. An examination of the mass posteriors shows that the median mass of the lens companions ranges from 0.02 $M_\odot$ to 0.05 $M_\odot$, indicating that these companions fall within the brown-dwarf mass range. The mass of the primary lenses ranges from 0.11 $M_\odot$ to 0.68 $M_\odot$, indicating that they are low-mass stars with substantially lower masses compared to the Sun. △ Less

Submitted 20 August, 2024; originally announced August 2024.

Comments: 13 pages, 17 figures, 12 tables

Analysis of the full Spitzer microlensing sample I: Dark remnant candidates and Gaia predictions

Authors: Krzysztof A. Rybicki, Yossi Shvartzvald, Jennifer C. Yee, Sebastiano Calchi Novati, Eran O. Ofek, Ian A. Bond, Charles Beichman, Geoff Bryden, Sean Carey, Calen Henderson, Wei Zhu, Michael M. Fausnaugh, Benjamin Wibking, Andrzej Udalski, Radek Poleski, Przemek Mróz, Michal K. Szymański, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Jan Skowron, Krzysztof Ulaczyk, Patryk Iwanek, Marcin Wrona, Yoon-Hyun Ryu , et al. (48 additional authors not shown)

Abstract: In the pursuit of understanding the population of stellar remnants within the Milky Way, we analyze the sample of $\sim 950$ microlensing events observed by the Spitzer Space Telescope between 2014 and 2019. In this study we focus on a sub-sample of nine microlensing events, selected based on their long timescales, small microlensing parallaxes and joint observations by the Gaia mission, to increa… ▽ More In the pursuit of understanding the population of stellar remnants within the Milky Way, we analyze the sample of $\sim 950$ microlensing events observed by the Spitzer Space Telescope between 2014 and 2019. In this study we focus on a sub-sample of nine microlensing events, selected based on their long timescales, small microlensing parallaxes and joint observations by the Gaia mission, to increase the probability that the chosen lenses are massive and the mass is measurable. Among the selected events we identify lensing black holes and neutron star candidates, with potential confirmation through forthcoming release of the Gaia time-series astrometry in 2026. Utilizing Bayesian analysis and Galactic models, along with the Gaia Data Release 3 proper motion data, four good candidates for dark remnants were identified: OGLE-2016-BLG-0293, OGLE-2018-BLG-0483, OGLE-2018-BLG-0662, and OGLE-2015-BLG-0149, with lens masses of $2.98^{+1.75}_{-1.28}~M_{\odot}$, $4.65^{+3.12}_{-2.08}~M_{\odot}$, $3.15^{+0.66}_{-0.64}~M_{\odot}$ and $1.4^{+0.75}_{-0.55}~M_{\odot}$, respectively. Notably, the first two candidates are expected to exhibit astrometric microlensing signals detectable by Gaia, offering the prospect of validating the lens masses. The methodologies developed in this work will be applied to the full Spitzer microlensing sample, populating and analyzing the time-scale ($t_{\rm E}$) vs. parallax ($π_{\rm E}$) diagram to derive constraints on the population of lenses in general and massive remnants in particular. △ Less

Submitted 18 July, 2024; originally announced July 2024.

Comments: submitted to ApJ

Weak-Lensing Shear-Selected Galaxy Clusters from the Hyper Suprime-Cam Subaru Strategic Program: II. Cosmological Constraints from the Cluster Abundance

Authors: I-Non Chiu, Kai-Feng Chen, Masamune Oguri, Markus M. Rau, Takashi Hamana, Yen-Ting Lin, Hironao Miyatake, Satoshi Miyazaki, Surhud More, Tomomi Sunayama, Sunao Sugiyama, Masahiro Takada

Abstract: We present cosmological constraints using the abundance of weak-lensing shear-selected galaxy clusters in the Hyper Suprime-Cam (HSC) Subaru Strategic Program. The clusters are selected on the mass maps constructed using the three-year (Y3) weak-lensing data with an area of $\approx500~$deg$^2$, resulting in a sample size of $129$ clusters with high signal-to-noise ratios $ν$ of $ν\geq4.7$. Owing… ▽ More We present cosmological constraints using the abundance of weak-lensing shear-selected galaxy clusters in the Hyper Suprime-Cam (HSC) Subaru Strategic Program. The clusters are selected on the mass maps constructed using the three-year (Y3) weak-lensing data with an area of $\approx500~$deg$^2$, resulting in a sample size of $129$ clusters with high signal-to-noise ratios $ν$ of $ν\geq4.7$. Owing to the deep, wide-field, and uniform imaging of the HSC survey, this is by far the largest sample of shear-selected clusters, in which the selection solely depends on gravity and is free from any assumptions about the dynamical state. Informed by the optical counterparts, the shear-selected clusters span a redshift range of $z\lesssim0.7$ with a median of $z\approx0.3$. The lensing sources are securely selected at $z\gtrsim0.7$ with a median of $z\approx1.3$, leading to nearly zero cluster member contamination. We carefully account for (1) the bias in the photometric redshift of sources, (2) the bias and scatter in the weak-lensing mass using a simulation-based calibration, and (3) the measurement uncertainty that is directly estimated on the mass maps using an injection-based method developed in a companion paper (Chen et al. submitted). In a blind analysis, the fully marginalized posteriors of the cosmological parameters are obtained as $Ω_{\mathrm{m}} = 0.50^{+0.28}_{-0.24}$, $σ_8 = 0.685^{+0.161}_{-0.088}$, $\hat{S}_{8}\equivσ_8\left(Ω_{\mathrm{m}}/0.3\right)^{0.25} = 0.835^{+0.041}_{-0.044}$, and $σ_8\left(Ω_{\mathrm{m}}/0.3\right)^{0.5} = 0.993^{+0.084}_{-0.126}$ in a flat $Λ$CDM model. We compare our cosmological constraints with other studies, including those based on cluster abundances, galaxy-galaxy lensing and clustering, and Cosmic Microwave Background observed by $Planck$, and find good agreement at levels of $\lesssim2σ$. [abridged] △ Less

Submitted 14 October, 2024; v1 submitted 17 June, 2024; originally announced June 2024.

Comments: Accepted for publication in the Open Journal of Astrophysics. Main results are Figures 11 and 12. The cluster catalog and the cosmological chain are accessible at https://github.com/inonchiu/hsc_shear_selected_clusters

Weak-Lensing Shear-Selected Galaxy Clusters from the Hyper Suprime-Cam Subaru Strategic Program: I. Cluster Catalog, Selection Function and Mass--Observable Relation

Authors: Kai-Feng Chen, I-Non Chiu, Masamune Oguri, Yen-Ting Lin, Hironao Miyatake, Satoshi Miyazaki, Surhud More, Takashi Hamana, Markus M. Rau, Tomomi Sunayama, Sunao Sugiyama, Masahiro Takada

Abstract: We present the first step toward deriving cosmological constraints through the abundances of galaxy clusters selected in a $510\,\mathrm{deg}^2$ weak-lensing aperture mass map, constructed with the Year-Three shear catalog from the Hyper Suprime-Cam Subaru Strategic Program. We adopt a conservative source galaxy selection to construct a sample of $129$ weak-lensing peaks with a signal-to-noise rat… ▽ More We present the first step toward deriving cosmological constraints through the abundances of galaxy clusters selected in a $510\,\mathrm{deg}^2$ weak-lensing aperture mass map, constructed with the Year-Three shear catalog from the Hyper Suprime-Cam Subaru Strategic Program. We adopt a conservative source galaxy selection to construct a sample of $129$ weak-lensing peaks with a signal-to-noise ratio above $4.7$. We use semi-analytical injection simulations to derive the selection function and the mass--observable relation of our sample. These results take into account complicated uncertainties associated with weak-lensing measurements, such as the non-uniform survey depth and the complex survey geometry, projection effects from uncorrelated large-scale structures, and the intrinsic alignment of source galaxies. We also propose a novel modeling framework to make parts of the mass--observable relation insensitive to assumed cosmological parameters. Such a framework not only offers a great computational advantage to cosmological studies, but can also benefit future astrophysical studies using shear-selected clusters. Our results are an important step toward utilizing these cluster samples that are constructed nearly independent of any baryonic assumptions in upcoming deep-and-wide lensing surveys from the Vera Rubin Observatory, Euclid, and the Nancy Grace Roman Space Telescope. △ Less

Submitted 3 January, 2025; v1 submitted 17 June, 2024; originally announced June 2024.

Comments: 18 pages, 9 figures; accepted for publication in the Open Journal of Astrophysics. The cluster catalog of the cosmological sample (signal-to-noise ratio above $4.7$) is accessible at https://github.com/inonchiu/hsc_shear_selected_clusters. See companion paper Chiu et al (arXiv:2406.11970) for cosmological constraints from this cluster sample

Four microlensing giant planets detected through signals produced by minor-image perturbations

Authors: Cheongho Han, Ian A. Bond, Chung-Uk Lee, Andrew Gould, Michael D. Albrow, Sun-Ju Chung, Kyu-Ha Hwang, Youn Kil Jung, 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, Fumio Abe, Ken Bando, Richard Barry , et al. (41 additional authors not shown)

Abstract: We investigated the nature of the anomalies appearing in four microlensing events KMT-2020-BLG-0757, KMT-2022-BLG-0732, KMT-2022-BLG-1787, and KMT-2022-BLG-1852. The light curves of these events commonly exhibit initial bumps followed by subsequent troughs that extend across a substantial portion of the light curves. We performed thorough modeling of the anomalies to elucidate their characteristic… ▽ More We investigated the nature of the anomalies appearing in four microlensing events KMT-2020-BLG-0757, KMT-2022-BLG-0732, KMT-2022-BLG-1787, and KMT-2022-BLG-1852. The light curves of these events commonly exhibit initial bumps followed by subsequent troughs that extend across a substantial portion of the light curves. We performed thorough modeling of the anomalies to elucidate their characteristics. Despite their prolonged durations, which differ from the usual brief anomalies observed in typical planetary events, our analysis revealed that each anomaly in these events originated from a planetary companion located within the Einstein ring of the primary star. It was found that the initial bump arouse when the source star crossed one of the planetary caustics, while the subsequent trough feature occurred as the source traversed the region of minor image perturbations lying between the pair of planetary caustics. The estimated masses of the host and planet, their mass ratios, and the distance to the discovered planetary systems are $(M_{\rm host}/M_\odot, M_{\rm planet}/M_{\rm J}, q/10^{-3}, \dl/{\rm kpc}) = (0.58^{+0.33}_{-0.30}, 10.71^{+6.17}_{-5.61}, 17.61\pm 2.25,6.67^{+0.93}_{-1.30})$ for KMT-2020-BLG-0757, $(0.53^{+0.31}_{-0.31}, 1.12^{+0.65}_{-0.65}, 2.01 \pm 0.07, 6.66^{+1.19}_{-1.84})$ for KMT-2022-BLG-0732, $(0.42^{+0.32}_{-0.23}, 6.64^{+4.98}_{-3.64}, 15.07\pm 0.86, 7.55^{+0.89}_{-1.30})$ for KMT-2022-BLG-1787, and $(0.32^{+0.34}_{-0.19}, 4.98^{+5.42}_{-2.94}, 8.74\pm 0.49, 6.27^{+0.90}_{-1.15})$ for KMT-2022-BLG-1852. These parameters indicate that all the planets are giants with masses exceeding the mass of Jupiter in our solar system and the hosts are low-mass stars with masses substantially less massive than the Sun. △ Less

Submitted 15 June, 2024; originally announced June 2024.

Comments: 10 pages, 12 figures, 7 tables

KMT-2023-BLG-1866Lb: Microlensing super-Earth around an M dwarf host

Authors: Cheongho Han, Ian A. Bond, Andrzej Udalski, Chung-Uk Lee, Andrew Gould, Michael D. Albrow, Sun-Ju Chung, Kyu-Ha Hwang, Youn Kil Jung, 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, Fumio Abe, Ken Bando , et al. (42 additional authors not shown)

Abstract: We investigate the nature of the short-term anomaly that appears in the lensing light curve of KMT-2023-BLG-1866. The anomaly was only partly covered due to its short duration, less than a day, coupled with cloudy weather conditions and restricted nighttime duration. Considering intricacy of interpreting partially covered signals, we thoroughly explore all potential degenerate solutions. Through t… ▽ More We investigate the nature of the short-term anomaly that appears in the lensing light curve of KMT-2023-BLG-1866. The anomaly was only partly covered due to its short duration, less than a day, coupled with cloudy weather conditions and restricted nighttime duration. Considering intricacy of interpreting partially covered signals, we thoroughly explore all potential degenerate solutions. Through this process, we identify three planetary scenarios that equally well account for the observed anomaly. These scenarios are characterized by the specific planetary parameters: $(s, q)_{\rm inner} = [0.9740 \pm 0.0083, (2.46 \pm 1.07) \times 10^{-5}]$, $(s, q)_{\rm intermediate} = [0.9779 \pm 0.0017, (1.56 \pm 0.25)\times 10^{-5}]$, and $(s, q)_{\rm outer} = [0.9894 \pm 0.0107, (2.31 \pm 1.29)\times 10^{-5}]$, where $s$ and $q$ denote the projected separation (scaled to the Einstein radius) and mass ratio between the planet and its host, respectively. We identify that the ambiguity between the inner and outer solutions stems from the inner-outer degeneracy, while the similarity between the intermediate solution and the others is due to an accidental degeneracy caused by incomplete anomaly coverage. Through Bayesian analysis utilizing the constraints derived from measured lensing observables and blending flux, our estimation indicates that the lens system comprises a very low-mass planet orbiting an early M-type star situated approximately (6.2 -- 6.5)~kpc from Earth in terms of median posterior values for the different solutions. The median mass of the planet host is in the range of (0.48 -- 0.51)~$M_\odot$, and that of the planet's mass spans a range of (2.6 -- 4.0)~$M_{\rm E}$, varying across different solutions. The detection of KMT-2023-BLG-1866Lb signifies the extension of the lensing surveys to very low-mass planets that have been difficult to be detected from earlier surveys. △ Less

Submitted 13 May, 2024; originally announced May 2024.

Comments: 9 pages, 8 figures, 4 tables

OGLE-2015-BLG-0845L: A low-mass M dwarf from the microlensing parallax and xallarap effects

Authors: Zhecheng Hu, Wei Zhu, Andrew Gould, Andrzej Udalski, Takahiro Sumi, Ping Chen, Sebastiano Calchi Novati, Jennifer C. Yee, Charles A. Beichman, Geoffery Bryden, Sean Carey, Michael Fausnaugh, B. Scott Gaudi, Calen B. Henderson, Yossi Shvartzvald, Benjamin Wibking, Przemek Mróz, Jan Skowron, Radosław Poleski, Michał K. Szymański, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof Ulaczyk, Krzysztof A. Rybicki , et al. (29 additional authors not shown)

Abstract: We present the analysis of the microlensing event OGLE-2015-BLG-0845, which was affected by both the microlensing parallax and xallarap effects. The former was detected via the simultaneous observations from the ground and Spitzer, and the latter was caused by the orbital motion of the source star in a relatively close binary. The combination of these two effects led to a mass measurement of the l… ▽ More We present the analysis of the microlensing event OGLE-2015-BLG-0845, which was affected by both the microlensing parallax and xallarap effects. The former was detected via the simultaneous observations from the ground and Spitzer, and the latter was caused by the orbital motion of the source star in a relatively close binary. The combination of these two effects led to a mass measurement of the lens object, revealing a low-mass ($0.14 \pm 0.05 M_{\odot}$) M-dwarf at the bulge distance ($7.6 \pm 1.0$ kpc). The source binary consists of a late F-type subgiant and a K-type dwarf of $\sim1.2 M_{\odot}$ and $\sim 0.9 M_{\odot}$, respectively, and the orbital period is $70 \pm 10$ days. OGLE-2015-BLG-0845 is the first single-lens event in which the lens mass is measured via the binarity of the source. Given the abundance of binary systems as potential microlensing sources, the xallarap effect may not be a rare phenomenon. Our work thus highlights the application of the xallarap effect in the mass determination of microlenses, and the same method can be used to identify isolated dark lenses. △ Less

Submitted 6 August, 2024; v1 submitted 19 April, 2024; originally announced April 2024.

Comments: New version after the review process. Accepted for publication in Monthly Notices of the Royal Astronomical Society

OGLE-2018-BLG-0971, MOA-2023-BLG-065, and OGLE-2023-BLG-0136: Microlensing events with prominent orbital effects

Authors: Cheongho Han, Andrzej Udalski, Ian A. Bond, Chung-Uk Lee, Andrew Gould, Michael D. Albrow, Sun-Ju Chung, Kyu-Ha Hwang, Youn Kil Jung, Hyoun-Woo Kim, 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, Przemek Mróz , et al. (38 additional authors not shown)

Abstract: We undertake a project to reexamine microlensing data gathered from high-cadence surveys. The aim of the project is to reinvestigate lensing events with light curves exhibiting intricate anomaly features associated with caustics, yet lacking prior proposed models to explain these features. Through detailed reanalyses considering higher-order effects, we identify that accounting for orbital motions… ▽ More We undertake a project to reexamine microlensing data gathered from high-cadence surveys. The aim of the project is to reinvestigate lensing events with light curves exhibiting intricate anomaly features associated with caustics, yet lacking prior proposed models to explain these features. Through detailed reanalyses considering higher-order effects, we identify that accounting for orbital motions of lenses is vital in accurately explaining the anomaly features observed in the light curves of the lensing events OGLE-2018-BLG-0971, MOA-2023-BLG-065, and OGLE-2023-BLG-0136. We estimate the masses and distances to the lenses by conducting Bayesian analyses using the lensing parameters of the newly found lensing solutions. From these analyses, we identify that the lenses of the events OGLE-2018-BLG-0971 and MOA-2023-BLG-065 are binaries composed of M dwarfs, while the lens of OGLE-2023-BLG-0136 is likely to be a binary composed of an early K-dwarf primary and a late M-dwarf companion. For all lensing events, the probability of the lens residing in the bulge is considerably higher than that of it being located in the disk. △ Less

Submitted 8 April, 2024; originally announced April 2024.

Comments: 11 pages, 13 figures, 6 tables

The New Horizons Extended Mission Target: Arrokoth Search and Discovery

Authors: Marc W. Buie, John R. Spencer, Simon B. Porter, Susan D. Benecchi, Alex H. Parker, S. Alan Stern, Michael Belton, Richard P. Binzel, David Borncamp, Francesca DeMeo, S. Fabbro, Cesar Fuentes, Hisanori Furusawa, Tetsuharu Fuse, Pamela L. Gay, Stephen Gwyn, Matthew J. Holman, H. Karoji, J. J. Kavelaars, Daisuke Kinoshita, Satoshi Miyazaki, Matt Mountain, Keith S. Noll, David J. Osip, Jean-Marc Petit , et al. (15 additional authors not shown)

Abstract: Following the Pluto fly-by of the New Horizons spacecraft, the mission provided a unique opportunity to explore the Kuiper Belt in-situ. The possibility existed to fly-by a Kuiper Belt object (KBO) as well as to observe additional objects at distances closer than are feasible from earth-orbit facilities. However, at the time of launch no KBOs were known about that were accessible by the spacecraft… ▽ More Following the Pluto fly-by of the New Horizons spacecraft, the mission provided a unique opportunity to explore the Kuiper Belt in-situ. The possibility existed to fly-by a Kuiper Belt object (KBO) as well as to observe additional objects at distances closer than are feasible from earth-orbit facilities. However, at the time of launch no KBOs were known about that were accessible by the spacecraft. In this paper we present the results of 10 years of observations and three uniquely dedicated efforts -- two ground-based using the Subaru Suprime Camera, the Magellan MegaCam and IMACS Cameras, and one with the Hubble Space Telescope -- to find such KBOs for study. In this paper we overview the search criteria and strategies employed in our work and detail the analysis efforts to locate and track faint objects in the galactic plane. We also present a summary of all of the KBOs that were discovered as part of our efforts and how spacecraft targetability was assessed, including a detailed description of our astrometric analysis which included development of an extensive secondary calibration network. Overall, these efforts resulted in the discovery of 89 KBOs including 11 which became objects for distant observation by New Horizons and (486958) Arrokoth which became the first post-Pluto fly-by destination. △ Less

Submitted 3 July, 2024; v1 submitted 7 March, 2024; originally announced March 2024.

Comments: Accepted to PSJ. 40 pages, 10 figures, 10 tables

The SRG-eROSITA All-Sky Survey : Constraints on f(R) Gravity from Cluster Abundance

Authors: E. Artis, V. Ghirardini, E. Bulbul, S. Grandis, C. Garrel, N. Clerc, R. Seppi, J. Comparat, M. Cataneo, Y. E. Bahar, F. Balzer, I. Chiu, D. Gruen, F. Kleinebreil, M. Kluge, S. Krippendorf, X. Li, A. Liu, A. Merloni, H. Miyatake, S. Miyazaki, K. Nandra, N. Okabe, F. Pacaud, P. Predehl , et al. (6 additional authors not shown)

Abstract: The evolution of the cluster mass function traces the growth of the linear density perturbations and can be utilized for constraining the parameters of cosmological and alternative gravity models. In this context, we present new constraints on potential deviations from general relativity by investigating the Hu-Sawicki parametrization of the f(R) gravity with the first SRG-eROSITA All-Sky Survey (… ▽ More The evolution of the cluster mass function traces the growth of the linear density perturbations and can be utilized for constraining the parameters of cosmological and alternative gravity models. In this context, we present new constraints on potential deviations from general relativity by investigating the Hu-Sawicki parametrization of the f(R) gravity with the first SRG-eROSITA All-Sky Survey (eRASS1) cluster catalog in the Western Galactic Hemisphere in combination with the overlapping Dark Energy Survey Year 3, KiloDegree Survey and Hyper Supreme Camera data for weak lensing mass calibration. For the first time, we present constraints obtained from cluster abundances only. When we consider massless neutrinos, we find a strict upper limit of log |fR0| < -4.31 at 95% confidence level. Massive neutrinos suppress structure growth at small scales, and thus have the opposite effect of f(R) gravity. We consequently investigate the joint fit of the mass of the neutrinos with the modified gravity parameter. We obtain log |fR0| < -4.12 jointly with \sum m_ν< 0.44 e.V. at 95% confidence level, tighter than the limits in the literature utilizing cluster counts only. At log |fR0|= - 6, the number of clusters is not significantly changed by the theory. Consequently, we do not find any statistical deviation from general relativity from the study of eRASS1 cluster abundance. Deeper surveys with eROSITA, increasing the number of detected clusters, will further improve constraints on log |fR0| and investigate alternative gravity theories. △ Less

Submitted 13 February, 2024; originally announced February 2024.

Comments: 13 pages, 6 figures, submitted to A&A

Journal ref: A&A 691, A301 (2024)

The SRG/eROSITA all-sky survey: Cosmology constraints from cluster abundances in the western Galactic hemisphere

Authors: V. Ghirardini, E. Bulbul, E. Artis, N. Clerc, C. Garrel, S. Grandis, M. Kluge, A. Liu, Y. E. Bahar, F. Balzer, I. Chiu, J. Comparat, D. Gruen, F. Kleinebreil, S. Krippendorf, A. Merloni, K. Nandra, N. Okabe, F. Pacaud, P. Predehl, M. E. Ramos-Ceja, T. H. Reiprich, J. S. Sanders, T. Schrabback, R. Seppi , et al. (24 additional authors not shown)

Abstract: The cluster mass function traces the growth of linear density perturbations and provides valuable insights into the growth of structures, the nature of dark matter, and the cosmological parameters governing the Universe. The primary science goal of eROSITA, on board the {\it Spectrum Roentgen Gamma (SRG)} mission, launched in 2019, is to constrain cosmology through the evolution of cluster mass fu… ▽ More The cluster mass function traces the growth of linear density perturbations and provides valuable insights into the growth of structures, the nature of dark matter, and the cosmological parameters governing the Universe. The primary science goal of eROSITA, on board the {\it Spectrum Roentgen Gamma (SRG)} mission, launched in 2019, is to constrain cosmology through the evolution of cluster mass function. In this paper, we present the cosmological constraints obtained from 5259 clusters of galaxies detected over an area of 12791~deg$^2$ in the Western Galactic Hemisphere of the eROSITA's first All-Sky Survey (eRASS1). The common footprint region between the eROSITA Survey and DES, KiDS, and HSC surveys is used for calibration of the scaling between X-ray count rate and their total mass through measurements of their weak gravitational lensing signal. eRASS1 cluster abundances constrain the $Λ$CDM parameters, which are the energy density of the total matter to $Ω_{\mathrm{m}}=0.29^{+0.01}_{-0.02}$, and the normalization of the density fluctuations to $σ_8=0.88\pm0.02$ and their combination yields $S_8=σ_8 (Ω_\mathrm{m} / 0.3)^{0.5}=0.86\pm0.01$, consistent and at a similar precision with the state-of-the-art CMB measurements. eRASS1 cosmological experiment places a most stringent upper limit on the summed masses of left-handed light neutrinos to $\sum m_ν< 0.22\mathrm{~eV}$ (95\% confidence interval). Combining eRASS1 cluster abundance measurements with CMB and ground-based neutrino oscillation experiments, we measure the summed neutrino masses to be $\sum m_ν=0.08_{-0.02}^{+0.03}\mathrm{~eV}$ or $\sum m_ν=0.12_{-0.01}^{+0.03}\mathrm{~eV}$ depending on the mass hierarchy scenario for neutrino eigenstates. eRASS1 cluster abundances significantly improve the constraints on the dark energy equation of state parameter to $w=-1.12\pm0.12$. (ABRIDGED) △ Less

Submitted 25 July, 2024; v1 submitted 13 February, 2024; originally announced February 2024.

Comments: 41 pages, 22 figures, Accepted for publication by A&A

Journal ref: A&A 689, A298 (2024)

The SRG/eROSITA All-Sky Survey: Weak-Lensing of eRASS1 Galaxy Clusters in KiDS-1000 and Consistency Checks with DES Y3 & HSC-Y3

Authors: Florian Kleinebreil, Sebastian Grandis, Tim Schrabback, Vittorio Ghirardini, I-Non Chiu, Ang Liu, Matthias Kluge, Thomas H. Reiprich, Emmanuel Artis, Emre Bahar, Fabian Balzer, Esra Bulbul, Nicolas Clerc, Johan Comparat, Christian Garrel, Daniel Gruen, Xiangchong Li, Hironao Miyatake, Satoshi Miyazaki, Miriam E. Ramos-Ceja, Jeremy Sanders, Riccardo Seppi, Nobuhiro Okabe, Xiaoyuan Zhang

Abstract: We aim to participate in the calibration of the X-ray photon count rate to halo mass scaling relation of galaxy clusters selected in the first eROSITA All-Sky Survey on the Western Galactic Hemisphere (eRASS1) using KiDS-1000 weak-lensing (WL) data. We measure the radial shear profiles around eRASS1 galaxy clusters using background galaxies in KiDS-1000, as well as the cluster member contamination… ▽ More We aim to participate in the calibration of the X-ray photon count rate to halo mass scaling relation of galaxy clusters selected in the first eROSITA All-Sky Survey on the Western Galactic Hemisphere (eRASS1) using KiDS-1000 weak-lensing (WL) data. We measure the radial shear profiles around eRASS1 galaxy clusters using background galaxies in KiDS-1000, as well as the cluster member contamination. Furthermore we provide consistency checks with the other stage-III WL surveys who take part in the eRASS1 mass calibration, DES Y3 and HSC-Y3. We determine the cluster member contamination of eRASS1 clusters present in KiDS-1000 based on source number density profiles, where we account for the obscuration caused by cluster galaxies. The extracted shear profiles, together with the contamination model and the lens sample selection, are then analysed through a Bayesian population model. We calibrate the WL mass bias parameter by analysing realistic synthetic shear profiles from mock cluster catalogues. Our consistency checks between KiDS-1000 and DES Y3 & HSC-Y3 include the comparison of contamination-corrected density contrast profiles employing the union of background sources around common clusters, as well as the individual scaling relation results. We present a global contamination model for eRASS1 clusters in KiDS-1000 and the calibration results of the X-ray photon count rate to halo mass relation. The results of the WL mass bias parameter show that the uncertainty of the multiplicative shear bias dominates the systematic error budget at low clusters redshifts while the uncertainty of our contamination model does at high ones. The cross-checks between the three WL surveys show that they are statistically consistent with each other. This enables for the first time cosmological constraints from clusters calibrated by three state-of-the-art WL surveys. (abridged) △ Less

Submitted 13 February, 2024; originally announced February 2024.

Comments: 22 pages, 23 figures

Journal ref: A&A 695, A216 (2025)

Dark lens candidates from Gaia Data Release 3

Authors: K. Kruszyńska, Ł. Wyrzykowski, K. A. Rybicki, K. Howil, M. Jabłońska, Z. Kaczmarek, N. Ihanec, M. Maskoliūnas, M. Bronikowski, U. Pylypenko, A. Udalski, P. Mróz, R. Poleski, J. Skowron, M. K. Szymański, I. Soszyński, P. Pietrukowicz, S. Kozłowski, K. Ulaczyk, P. Iwanek, M. Wrona, M. Gromadzki, M. J. Mróz, F. Abe, K. Bando , et al. (26 additional authors not shown)

Abstract: Gravitational microlensing is a phenomenon that allows us to observe dark remnants of stellar evolution even if they no longer emit electromagnetic radiation. In particular, it can be useful to observe solitary neutron stars or stellar-mass black holes, providing a unique window through which to understand stellar evolution. Obtaining direct mass measurements with this technique requires precise o… ▽ More Gravitational microlensing is a phenomenon that allows us to observe dark remnants of stellar evolution even if they no longer emit electromagnetic radiation. In particular, it can be useful to observe solitary neutron stars or stellar-mass black holes, providing a unique window through which to understand stellar evolution. Obtaining direct mass measurements with this technique requires precise observations of both the change in brightness and the position of the microlensed star. The European Space Agency's Gaia satellite can provide both. Using publicly available data from different surveys, we analysed events published in the Gaia Data Release 3 (Gaia DR3) microlensing catalogue. Here we describe our selection of candidate dark lenses, where we suspect the lens is a white dwarf (WD), a neutron star (NS), a black hole (BH), or a mass-gap object, with a mass in a range between the heaviest NS and the least massive BH. We estimated the mass of the lenses using information obtained from the best-fitting microlensing models, the source star, the Galactic model and the expected distribution of the parameters. We found eleven candidates for dark remnants: one WDs, three NS, three mass-gap objects, and four BHs. △ Less

Submitted 17 September, 2024; v1 submitted 24 January, 2024; originally announced January 2024.

Comments: Accepted to Astronomy&Astrophysics, 20 pages, 4 figures, 6 tables

Journal ref: A&A 692, A28 (2024)

MOA-2022-BLG-563Lb, KMT-2023-BLG-0469Lb, and KMT-2023-BLG-0735Lb: Three sub-Jovian-mass microlensing planets

Authors: Cheongho Han, Youn Kil Jung, Ian A. Bond, Andrew Gould, Michael D. Albrow, Sun-Ju Chung, Kyu-Ha Hwang, Chung-Uk Lee, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Hongjing Yang, Jennifer C. Yee, Weicheng Zang, Sang-Mok Cha, Doeon Kim, Dong-Jin Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Fumio Abe, Richard Barry, David P. Bennett , et al. (23 additional authors not shown)

Abstract: We analyze the anomalies appearing in the light curves of the three microlensing events MOA-2022-BLG-563, KMT-2023-BLG-0469, and KMT-2023-BLG-0735. The anomalies exhibit common short-term dip features that appear near the peak. From the detailed analyses of the light curves, we find that the anomalies were produced by planets accompanied by the lenses of the events. For all three events, the estim… ▽ More We analyze the anomalies appearing in the light curves of the three microlensing events MOA-2022-BLG-563, KMT-2023-BLG-0469, and KMT-2023-BLG-0735. The anomalies exhibit common short-term dip features that appear near the peak. From the detailed analyses of the light curves, we find that the anomalies were produced by planets accompanied by the lenses of the events. For all three events, the estimated mass ratios between the planet and host are on the order of $10^{-4}$: $q\sim 8 \times 10^{-4}$ for MOA-2022-BLG-563L, $q\sim 2.5\times 10^{-4}$ for KMT-2023-BLG-0469L, and $q\sim 1.9\times 10^{-4}$ for KMT-2023-BLG-0735L. The interpretations of the anomalies are subject to a common inner-outer degeneracy, which causes ambiguity when estimating the projected planet-host separation. We estimated the planet mass, $M_{\rm p}$, host mass, $M_{\rm h}$, and distance, $D_{\rm L}$, to the planetary system by conducting Bayesian analyses using the observables of the events. The estimated physical parameters of the planetary systems are $(M_{\rm h}/M_\odot, M_{\rm p}/M_{\rm J}, D_{\rm L}/{\rm kpc}) = (0.48^{+0.36}_{-0.30}, 0.40^{+0.31}_{-0.25}, 6.53^{+1.12}_{-1.57})$ for MOA-2022-BLG-563L, $(0.47^{+0.35}_{-0.26}, 0.124^{+0.092}_{-0.067}, 7.07^{+1.03}_{-1.19})$ for KMT-2023-BLG-0469L, and $(0.62^{+0.34}_{-0.35}, 0.125^{+0.068}_{-0.070}, 6.26^{+1.27}_{-1.67})$ for KMT-2023-BLG-0735L. According to the estimated parameters, all planets are cold planets with projected separations that are greater than the snow lines of the planetary systems, they have masses that lie between the masses of Uranus and Jupiter of the Solar System, and the hosts of the planets are main-sequence stars that are less massive than the Sun. △ Less

Submitted 20 January, 2024; originally announced January 2024.

Comments: 11 pages, 7 tables, 10 figures

Systematic KMTNet Planetary Anomaly Search. XI. Complete Sample of 2016 Sub-Prime Field Planets

Authors: In-Gu Shin, Jennifer C. Yee, Weicheng Zang, Cheongho Han, Hongjing Yang, Andrew Gould, Chung-Uk Lee, Andrzej Udalski, Takahiro Sumi, Michael D. Albrow, Sun-Ju Chung, Kyu-Ha Hwang, Youn Kil Jung, Yoon-Hyun Ryu, Yossi Shvartzvald, Sang-Mok Cha, Dong-Jin Kim, Hyoun-Woo Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz, Michał K. Szymański , et al. (41 additional authors not shown)

Abstract: Following Shin et al. (2023b), which is a part of the Systematic KMTNet Planetary Anomaly Search series (i.e., a search for planets in the 2016 KMTNet prime fields), we conduct a systematic search of the 2016 KMTNet sub-prime fields using a semi-machine-based algorithm to identify hidden anomalous events missed by the conventional by-eye search. We find four new planets and seven planet candidates… ▽ More Following Shin et al. (2023b), which is a part of the Systematic KMTNet Planetary Anomaly Search series (i.e., a search for planets in the 2016 KMTNet prime fields), we conduct a systematic search of the 2016 KMTNet sub-prime fields using a semi-machine-based algorithm to identify hidden anomalous events missed by the conventional by-eye search. We find four new planets and seven planet candidates that were buried in the KMTNet archive. The new planets are OGLE-2016-BLG-1598Lb, OGLE-2016-BLG-1800Lb, MOA-2016-BLG-526Lb, and KMT-2016-BLG-2321Lb, which show typical properties of microlensing planets, i.e., giant planets orbit M dwarf host stars beyond their snow lines. For the planet candidates, we find planet/binary or 2L1S/1L2S degeneracies, which are an obstacle to firmly claiming planet detections. By combining the results of Shin et al. (2023b) and this work, we find a total of nine hidden planets, which is about half the number of planets discovered by eye in 2016. With this work, we have met the goal of the systematic search series for 2016, which is to build a complete microlensing planet sample. We also show that our systematic searches significantly contribute to completing the planet sample, especially for planet/host mass ratios smaller than $10^{-3}$, which were incomplete in previous by-eye searches of the KMTNet archive. △ Less

Submitted 8 January, 2024; originally announced January 2024.

Comments: 63 pages, 16 Tables, 19 Figures, Submitted in the AAS journal

KMT-2023-BLG-1431Lb: A New $q < 10^{-4}$ Microlensing Planet from a Subtle Signature

Authors: Aislyn Bell, Jiyuan Zhang, Youn Kil Jung, Jennifer C. Yee, Hongjing Yang, Takahiro Sumi, Andrzej Udalski, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Cheongho Han, Kyu-Ha Hwang, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Weicheng Zang, Sang-Mok Cha, Dong-Jin Kim, Seung-Lee Kim, Chung-Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Yunyi Tang , et al. (48 additional authors not shown)

Abstract: The current studies of microlensing planets are limited by small number statistics. Follow-up observations of high-magnification microlensing events can efficiently form a statistical planetary sample. Since 2020, the Korea Microlensing Telescope Network (KMTNet) and the Las Cumbres Observatory (LCO) global network have been conducting a follow-up program for high-magnification KMTNet events. Here… ▽ More The current studies of microlensing planets are limited by small number statistics. Follow-up observations of high-magnification microlensing events can efficiently form a statistical planetary sample. Since 2020, the Korea Microlensing Telescope Network (KMTNet) and the Las Cumbres Observatory (LCO) global network have been conducting a follow-up program for high-magnification KMTNet events. Here, we report the detection and analysis of a microlensing planetary event, KMT-2023-BLG-1431, for which the subtle (0.05 magnitude) and short-lived (5 hours) planetary signature was characterized by the follow-up from KMTNet and LCO. A binary-lens single-source (2L1S) analysis reveals a planet/host mass ratio of $q = (0.72 \pm 0.07) \times 10^{-4}$, and the single-lens binary-source (1L2S) model is excluded by $Δχ^2 = 80$. A Bayesian analysis using a Galactic model yields estimates of the host star mass of $M_{\rm host} = 0.57^{+0.33}_{-0.29}~M_\odot$, the planetary mass of $M_{\rm planet} = 13.5_{-6.8}^{+8.1}~M_{\oplus}$, and the lens distance of $D_{\rm L} = 6.9_{-1.7}^{+0.8}$ kpc. The projected planet-host separation of $a_\perp = 2.3_{-0.5}^{+0.5}$ au or $a_\perp = 3.2_{-0.8}^{+0.7}$, subject to the close/wide degeneracy. We also find that without the follow-up data, the survey-only data cannot break the degeneracy of central/resonant caustics and the degeneracy of 2L1S/1L2S models, showing the importance of follow-up observations for current microlensing surveys. △ Less

Submitted 21 November, 2023; originally announced November 2023.

Comments: PASP submitted. arXiv admin note: text overlap with arXiv:2301.06779

Final Results of Search for New Milky Way Satellites in the Hyper Suprime-Cam Subaru Strategic Program Survey: Discovery of Two More Candidates

Authors: Daisuke Homma, Masashi Chiba, Yutaka Komiyama, Masayuki Tanaka, Sakurako Okamoto, Mikito Tanaka, Miho N. Ishigaki, Kohei Hayashi, Nobuo Arimoto, Robert H. Lupton, Michael A. Strauss, Satoshi Miyazaki, Shiang-Yu Wang, Hitoshi Murayama

Abstract: We present the final results of our search for new Milky Way (MW) satellites using the data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) survey over $\sim 1,140$ deg$^2$. In addition to three candidates that we already reported, we have identified two new MW satellite candidates in the constellation of Sextans at a heliocentric distance of $D_{\odot} \simeq 126$kpc, and Virgo at… ▽ More We present the final results of our search for new Milky Way (MW) satellites using the data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) survey over $\sim 1,140$ deg$^2$. In addition to three candidates that we already reported, we have identified two new MW satellite candidates in the constellation of Sextans at a heliocentric distance of $D_{\odot} \simeq 126$kpc, and Virgo at $D_{\odot} \simeq 151$kpc, named Sextans II and Virgo III, respectively. Their luminosities (Sext II:$M_V\simeq-3.9$mag; Vir III:$M_V\simeq-2.7$mag) and half-light radii (Sext II:$r_h\simeq154$ pc; Vir III:$r_h\simeq 44$ pc) place them in the region of size-luminosity space of ultra-faint dwarf galaxies (UFDs). Including four previously known satellites, there are a total of nine satellites in the HSC-SSP footprint. This discovery rate of UFDs is much higher than that predicted from the recent models for the expected population of MW satellites in the framework of cold dark matter models, thereby suggesting that we encounter a too many satellites problem. Possible solutions to settle this tension are also discussed. △ Less

Submitted 30 April, 2024; v1 submitted 9 November, 2023; originally announced November 2023.

Comments: 20 pages, 17 figures, 4 tables, accepted for publication in PASJ

Systematic Reanalysis of KMTNet microlensing events, Paper I: Updates of the Photometry Pipeline and a New Planet Candidate

Authors: Hongjing Yang, Jennifer C. Yee, Kyu-Ha Hwang, Qiyue Qian, Ian A. Bond, Andrew Gould, Zhecheng Hu, Jiyuan Zhang, Shude Mao, Wei Zhu, Michael D. Albrow, Sun-Ju Chung, Cheongho Han, Youn Kil Jung, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Sang-Mok Cha, Dong-Jin Kim, Hyoun-Woo Kim, Seung-Lee Kim, Chung-Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park , et al. (30 additional authors not shown)

Abstract: In this work, we update and develop algorithms for KMTNet tender-love care (TLC) photometry in order to create an new, mostly automated, TLC pipeline. We then start a project to systematically apply the new TLC pipeline to the historic KMTNet microlensing events, and search for buried planetary signals. We report the discovery of such a planet candidate in the microlensing event MOA-2019-BLG-421/K… ▽ More In this work, we update and develop algorithms for KMTNet tender-love care (TLC) photometry in order to create an new, mostly automated, TLC pipeline. We then start a project to systematically apply the new TLC pipeline to the historic KMTNet microlensing events, and search for buried planetary signals. We report the discovery of such a planet candidate in the microlensing event MOA-2019-BLG-421/KMT-2019-BLG-2991. The anomalous signal can be explained by either a planet around the lens star or the orbital motion of the source star. For the planetary interpretation, despite many degenerate solutions, the planet is most likely to be a Jovian planet orbiting an M or K dwarf, which is a typical microlensing planet. The discovery proves that the project can indeed increase the sensitivity of historic events and find previously undiscovered signals. △ Less

Submitted 8 November, 2023; originally announced November 2023.

Comments: 19 pages, 13 figures, 7 tables. Submitted to MNRAS

OGLE-2014-BLG-0221Lb: A Jupiter Mass Ratio Companion Orbiting either a Late-Type Star or a Stellar Remnant

Authors: Rintaro Kirikawa, Takahiro Sumi, David P. Bennett, Daisuke Suzuki, Naoki Koshimoto, Shota Miyazaki, Ian A. Bond, Andrzej Udalski, Nicholas J. Rattenbury, Fumio Abe, Richard Barry, Aparna Bhattacharya, Hirosane Fujii, Akihiko Fukui, Ryusei Hamada, Yuki Hirao, Stela Ishitani Silva, Yoshitaka Itow, Yutaka Matsubara, Yasushi Muraki, Greg Olmschenk, Clément Ranc, Yuki K. Satoh, Mio Tomoyoshi, Paul . J. Tristram , et al. (11 additional authors not shown)

Abstract: We present the analysis of microlensing event OGLE-2014-BLG-0221, a planetary candidate event discovered in 2014. The photometric light curve is best described by a binary-lens single-source model. Our light curve modeling finds two degenerate models, with event timescales of $t_\mathrm{E}\sim70$ days and $\sim110$ days. These timescales are relatively long, indicating that the discovered system w… ▽ More We present the analysis of microlensing event OGLE-2014-BLG-0221, a planetary candidate event discovered in 2014. The photometric light curve is best described by a binary-lens single-source model. Our light curve modeling finds two degenerate models, with event timescales of $t_\mathrm{E}\sim70$ days and $\sim110$ days. These timescales are relatively long, indicating that the discovered system would possess a substantial mass. The two models are similar in their planetary parameters with a Jupiter mass ratio of $q \sim 10^{-3}$ and a separation of $s \sim 1.1$. While the shorter timescale model shows marginal detection of a microlensing parallax signal, the longer timescale model requires a higher order effect of microlensing parallax, lens orbital motion or xallarap to explain the deviation in the light curve. However, the modeling shows significant correlation between the higher order effects and suffers the ecliptic degeneracy that results in a failure to determine the parallax parameters. Bayesian inference is used to estimate the physical parameters of the lens, revealing the lens to be either a late-type star supported by the shorter timescale model or a stellar remnant supported by the longer timescale model. If the lens is a remnant, this would be the second planet found by microlensing around a stellar remnant. Since the models predict different values for relative proper motion and source flux, future high angular resolution follow-up observations (e.g. Keck adaptive optics) are required to rule out either of the models. △ Less

Submitted 19 October, 2023; originally announced October 2023.

Comments: 15 pages, 11 figures. Submitted to the AAS journals

Observing Cosmic-Ray Extensive Air Showers with a Silicon Imaging Detector

Authors: Satoshi Kawanomoto, Michitaro Koike, Fraser Bradfield, Toshihiro Fujii, Yutaka Komiyama, Satoshi Miyazaki, Tomoki Morokuma, Hitoshi Murayama, Masamune Oguri, Tsuyoshi Terai

Abstract: Extensive air showers induced from high-energy cosmic rays provide a window into understanding the most energetic phenomena in the universe. We present a new method for observing these showers using the silicon imaging detector Subaru Hyper Suprime-Cam (HSC). This method has the advantage of being able to measure individual secondary particles. When paired with a surface detector array, silicon im… ▽ More Extensive air showers induced from high-energy cosmic rays provide a window into understanding the most energetic phenomena in the universe. We present a new method for observing these showers using the silicon imaging detector Subaru Hyper Suprime-Cam (HSC). This method has the advantage of being able to measure individual secondary particles. When paired with a surface detector array, silicon imaging detectors like Subaru HSC will be useful for studying the properties of extensive air showers in detail. The following report outlines the first results of observing extensive air showers with Subaru HSC. The potential for reconstructing the incident direction of primary cosmic rays is demonstrated and possible interdisciplinary applications are discussed. △ Less

Submitted 11 October, 2023; originally announced October 2023.

Comments: 12 pages, 4 figures, 3 tables, published in Scientific Reports 13, 16091 (2023)

Journal ref: Scientific Reports 13, 16091 (2023)

Evidence that the Occurrence Rate of Hot Jupiters around Sun-like Stars Decreases with Stellar Age

Authors: Shota Miyazaki, Kento Masuda

Abstract: We investigate how the occurrence rate of giant planets (minimum mass $> 0.3\, M_\mathrm{Jup}$) around Sun-like stars depends on the age, mass, and metallicity of their host stars. We develop a hierarchical Bayesian framework to infer the number of planets per star (NPPS) as a function of both planetary and stellar parameters. The framework fully takes into account the uncertainties in the latter… ▽ More We investigate how the occurrence rate of giant planets (minimum mass $> 0.3\, M_\mathrm{Jup}$) around Sun-like stars depends on the age, mass, and metallicity of their host stars. We develop a hierarchical Bayesian framework to infer the number of planets per star (NPPS) as a function of both planetary and stellar parameters. The framework fully takes into account the uncertainties in the latter by utilizing the posterior samples for the stellar parameters obtained by fitting stellar isochrone models to the spectroscopic parameters, Gaia DR3 parallaxes, and 2MASS $K_{\rm s}$-band magnitudes adopting a certain bookkeeping prior. We apply the framework to 46 Doppler giants found around a sample of 382 Sun-like stars from the California Legacy Survey catalog that publishes spectroscopic parameters and search completeness for all the surveyed stars. We find evidence that the NPPS of hot Jupiters (orbital period $P=1$-$10\,\mathrm{days}$) decreases roughly in the latter half of the main sequence over the timescale of $\mathcal{O}(\mathrm{Gyr})$, while that of cold Jupiters ($P=1$-$10\,\mathrm{yr}$) does not. Assuming that this decrease is real and caused by tidal orbital decay, the modified stellar tidal quality factor $Q^\prime_\star$ is implied to be $\mathcal{O}(10^6)$ for a Sun-like main-sequence star orbited by a Jupiter-mass planet with $P\approx 3\,\mathrm{days}$. △ Less

Submitted 25 September, 2023; originally announced September 2023.

Comments: Accepted by the Astronomical Journal, 19 pages, 11 figures

KMT-2021-BLG-1547Lb: Giant microlensing planet detected through a signal deformed by source binarity

Authors: Cheongho Han, Weicheng Zang, Youn Kil Jung, Ian A. Bond, Sun-Ju Chung, Michael D. Albrow, Andrew Gould, Kyu-Ha Hwang, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Hongjing Yang, Jennifer C. Yee, Sang-Mok Cha, Doeon Kim, Dong-Jin Kim, Seung-Lee Kim, Chung-Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, L. A. G. Monard, Qiyue Qian, Zhuokai Liu , et al. (30 additional authors not shown)

Abstract: We investigate the previous microlensing data collected by the KMTNet survey in search of anomalous events for which no precise interpretations of the anomalies have been suggested. From this investigation, we find that the anomaly in the lensing light curve of the event KMT-2021-BLG-1547 is approximately described by a binary-lens (2L1S) model with a lens possessing a giant planet, but the model… ▽ More We investigate the previous microlensing data collected by the KMTNet survey in search of anomalous events for which no precise interpretations of the anomalies have been suggested. From this investigation, we find that the anomaly in the lensing light curve of the event KMT-2021-BLG-1547 is approximately described by a binary-lens (2L1S) model with a lens possessing a giant planet, but the model leaves unexplained residuals. We investigate the origin of the residuals by testing more sophisticated models that include either an extra lens component (3L1S model) or an extra source star (2L2S model) to the 2L1S configuration of the lens system. From these analyses, we find that the residuals from the 2L1S model originate from the existence of a faint companion to the source. The 2L2S solution substantially reduces the residuals and improves the model fit by $Δχ^2=67.1$ with respect to the 2L1S solution. The 3L1S solution also improves the fit, but its fit is worse than that of the 2L2S solution by $Δχ^2=24.7$. According to the 2L2S solution, the lens of the event is a planetary system with planet and host masses $(M_{\rm p}/M_{\rm J}, M_{\rm h}/M_\odot)=\left( 1.47^{+0.64}_{-0.77}, 0.72^{+0.32}_{-0.38}\right)$ lying at a distance $\D_{\rm L} =5.07^{+0.98}_{-1.50}$~kpc, and the source is a binary composed of a subgiant primary of a late G or an early K spectral type and a main-sequence companion of a K spectral type. The event demonstrates the need of sophisticated modeling for unexplained anomalies for the construction of a complete microlensing planet sample. △ Less

Submitted 3 September, 2023; originally announced September 2023.

Comments: 9 pages, 4 tables, 7 figures