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A Search For Stellar-mass Black Holes Via Astrometric Microlensing II: 2012-2015 Keck Candidates
Mace J. Huston, Jessica R. Lu, Casey Y. Lam +58
The Milky Way is expected to host 10 stellar-mass black holes with an uncertain binary fraction. The only proven method to detect isolated stellar mass black holes is gra…
Incorporating physical source parameters into microlensing modeling
Mateusz J. Mróz, Radosław Poleski, Andrzej Udalski +14
Modeling of complex microlensing events suffers from many difficult-to-disentangle degeneracies. This is especially the case for orbital motion of the source in a binary system, th…
Four-Body Gravitational Microlensing Events Involving Both a Binary Lens and a Binary Source
Cheongho Han, Chung-Uk Lee, Andrzej Udalski +31
We present detailed analyses of three anomalous microlensing events--KMT-2021-BLG-0209, KMT-2021-BLG-0901, and OGLE-2025-BLG-0356--identified from a systematic re-examination of KM…
Thirty Circumbinary Disk Occultation Systems (KH 15D-like stars) from the OGLE Project
M. A. Urbanowicz, I. Soszyński, P. Pietrukowicz +14
We present a catalog of 30 stars that are candidates for KH 15D-like binary systems, in which the observed brightness variations are caused by a circumbinary dusty disk that period…
Candidate Microlensing Brown Dwarfs in Binary Lens Systems from the 2023--2025 Observing Seasons
Cheongho Han, Andrzej Udalski, Ian A. Bond +62
We present detailed light-curve analyses of ten binary-lens microlensing events observed during the 2023--2025 seasons and selected as candidates for hosting brown-dwarf companions…
Six binary brown dwarf candidates identified by microlensing
Cheongho Han, Chung-Uk Lee, Ian A. Bond +57
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…
Doubling the Number of Blue Large-Amplitude Pulsators: Final Results of Searches for BLAPs in the OGLE Inner Galactic Bulge Fields
J. Borowicz, P. Pietrukowicz, J. Skowron +13
Blue Large-Amplitude Pulsators (BLAPs) are rare short-period (80 min) pulsating variable stars exhibiting large-amplitude brightness variations (typically between 0.1 and…
Three binary-source binary-lens microlensing events from the 2024 microlensing campaign
Cheongho Han, Chung-Uk Lee, Andrzej Udalski +27
We investigated microlensing events detected by the OGLE and KMTNet surveys during the 2024 observing season, focusing on those that exhibit very complex anomaly features. Through…
Spectroscopic Observations of Four Candidates for Blue Large-Amplitude Pulsators. No BLAPs at High Galactic Latitudes
P. Pietrukowicz, M. Latour, F. Di Mille +3
We have obtained spectroscopic observations for four short-period variable objects detected in ZTF, Gaia, and Pan-STARRS (ZGP) data and classified as Blue Large-Amplitude Pulsators…
The Ultimate I-band Calibration of the TRGB Standard Candle
A. Udalski, D. M. Skowron, J. Skowron +13
We present the ultimate I-band calibration of the tip of the red giant branch (TRGB) standard candle. Our calibration is based on photometry from the outer parts of the Large Magel…
Asteroseismology of Long-Period Variables with OGLE-IV data: Using Global Seismic Parameters as Luminosity Indicators
Qiang Xiong, Tanda Li, Jie Yu +19
Long-period variables (LPVs) are high-luminosity red giants or supergiants with pulsation periods ranging from days to years. Many LPVs in the Large Magellanic Cloud (LMC) and Gala…
The OGLE Collection of Variable Stars. Over 75 000 Eclipsing and Ellipsoidal Binary Systems in the Magellanic Clouds
M. Głowacki, I. Soszyński, A. Udalski +14
We present an updated collection of eclipsing and ellipsoidal binary systems in the Large and Small Magellanic Clouds (LMC and SMC), as observed by the Optical Gravitational Lensin…
Analyses of anomalous lensing events detected from the UKIRT microlensing survey
Cheongho Han, Weicheng Zang, Andrzej Udalski +61
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…
An Extremely Hot Pulsating Pre-White Dwarf from OGLE
P. Pietrukowicz, K. Werner, M. J. Mroz +1
We show that the blue 18.3-minute variable object discovered in the Galactic disk by the OGLE-III survey and named OGLE-GD-WD-0001 is a pulsating pre-white dwarf of PG 1159 spectra…
KMT-2021-BLG-0284, KMT-2022-BLG-2480, and KMT-2024-BLG-0412: Three microlensing events involving two lens masses and two source stars
Cheongho Han, Andrzej Udalski, Ian A. Bond +59
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…
Millinovae: A New Class of Transient Supersoft X-ray Sources without a Classical Nova Eruption
Przemek Mróz, Krzysztof Król, Hélène Szegedi +18
Some accreting binary systems containing a white dwarf (such as classical novae or persistent supersoft sources) are seen to emit low-energy X-rays with temperatures of ~10^6 K and…
Microlensing brown-dwarf companions in binaries detected during the 2022 and 2023 seasons
Cheongho Han, Ian A. Bond, Andrzej Udalski +63
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 Netw…
The OGLE Collection of Variable Stars: Over 18 000 Rotating Variables toward the Galactic Bulge
P. Iwanek, I. Soszyński, K. Stępień +14
Stellar rotation, a key factor influencing stellar structure and evolution, also drives magnetic activity, which is manifested as spots or flares on stellar surface. Here, we prese…
Blue Large-Amplitude Pulsators and Other Short-Period Variable Stars in OGLE-IV Fields of the Outer Galactic Bulge
J. Borowicz, P. Pietrukowicz, J. Skowron +13
In this work, we search the OGLE-IV outer Galactic bulge fields for short-period variable objects. The investigation focuses on unexplored timescales roughly below one hour in an a…
OGLE-2018-BLG-0971, MOA-2023-BLG-065, and OGLE-2023-BLG-0136: Microlensing events with prominent orbital effects
Cheongho Han, Andrzej Udalski, Ian A. Bond +60
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 int…
Observational Parameters of Blue Large-amplitude Pulsators
P. Pietrukowicz, M. Latour, I. Soszynski +15
Blue large-amplitude pulsators (BLAPs) are a recently discovered class of short-period pulsating variable stars. In this work, we present new information on these stars based on ph…
OGLE-2015-BLG-0845L: A low-mass M dwarf from the microlensing parallax and xallarap effects
Zhecheng Hu, Wei Zhu, Andrew Gould +51
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 sim…
Discovery of the Longest-Period Classical Cepheid in the Milky Way
I. Soszyński, D. M. Skowron, A. Udalski +12
We report the discovery of the classical Cepheid OGLE-GD-CEP-1884 (= GDS_J1535467-555656) with the longest pulsation period known in our Galaxy. The period of 78.14 d is nearly 10…
The OGLE Collection of Variable Stars. Over 15 000 Delta Scuti Stars in the Large Magellanic Cloud
I. Soszyński, P. Pietrukowicz, A. Udalski +12
We present the OGLE collection of delta Scuti stars in the Large Magellanic Cloud and in its foreground. Our dataset encompasses a total of 15 256 objects, constituting the largest…