Browsing by Author "Kruszyńska K"

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    Analysis of the Full Spitzer Microlensing Sample. I. Dark Remnant Candidates and Gaia Predictions
    (American Astronomical Society, 2024-11-10) Rybicki KA; Shvartzvald Y; Yee JC; Novati SC; Ofek EO; Bond IA; Beichman C; Bryden G; Carey S; Henderson C; Zhu W; Fausnaugh MM; Wibking B; Udalski A; Poleski R; Mróz P; Szymański MK; Soszyński I; Pietrukowicz P; Kozłowski S; Skowron J; Ulaczyk K; Iwanek P; Wrona M; Ryu Y-H; Albrow MD; Chung S-J; Gould A; Han C-H; Hwang K-H; Jung YK; Shin I-G; Yang H; Zang W; Cha S-M; Kim D-J; Kim H-W; Kim S-L; Lee C-U; Lee D-J; Lee Y; Park B-G; Pogge RW; Abe F; Barry R; Bennett DP; Bhattacharya A; Fukui A; Hamada R; Hamada S; Hamasaki N; Hirao Y; Ishitani Silva S; Itow Y; Kirikawa R; Koshimoto N; Matsubara Y; Miyazaki S; Muraki Y; Nagai T; Nunota K; Olmschenk G; Ranc C; Rattenbury NJ; Satoh YK; Sumi T; Suzuki D; Tristram PJ; Vandorou A; Yama H; Wyrzykowski Ł; Howil K; Kruszyńska K
    In the pursuit of understanding the population of stellar remnants within the Milky Way, we analyze the sample of ∼950 microlensing events observed by the Spitzer Space Telescope between 2014 and 2019. In this study we focus on a subsample 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 3.0-1.3+1.8M☉, 4.7-2.1+3.2 M☉, 3.15-0.64+0..66 M☉ and 1.40-0.55+0.75 M☉, 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 timescale (tE) versus parallax (πE) diagram to derive constraints on the population of lenses in general and massive remnants in particular.
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    Dark lens candidates from Gaia Data Release 3
    (EDP Sciences, France, for The European Southern Observatory, 2024-12) Kruszyńska K; Wyrzykowski L; Rybicki KA; Howil K; Jablońska M; Kaczmarek Z; Ihanec N; Maskoliūnas M; Bronikowski M; Pylypenko U; Udalski A; Mróz P; Poleski R; Skowron J; Szymański MK; Soszyński I; Pietrukowicz P; Kozlowski S; Ulaczyk K; Iwanek P; Wrona M; Gromadzki M; Mróz MJ; Abe F; Bando K; Barry R; Bennett DP; Bhattacharya A; Bond IA; Fukui A; Hamada R; Hamada S; Hamasaki N; Hirao Y; Ishitani Silva S; Itow Y; Koshimoto N; Matsubara Y; Miyazaki S; Muraki Y; Nagai T; Nunota K; Olmschenk G; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Tristram PJ; Vandorou A; Yama H
    Gravitational microlensing is a phenomenon that allows us to observe the dark remnants of stellar evolution, even if these bodies are no longer emitting 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 the 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, source star, Galactic model, and the expected parameter distributions. We found eleven candidates for dark remnants: one WDs, three NSs, three mass-gap objects, and four BHs.
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    MOA-2020-BLG-208Lb: Cool Sub-Saturn-mass Planet within Predicted Desert
    (American Astronomical Society, 2023-03) Olmschenk G; Bennett DP; Bond IA; Zang W; Jung YK; Yee JC; Bachelet E; Abe F; Barry RK; Bhattacharya A; Fujii H; Fukui A; Hirao Y; Silva SI; Itow Y; Kirikawa R; Kondo I; Koshimoto N; Matsubara Y; Matsumoto S; Miyazaki S; Munford B; Muraki Y; Okamura A; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Toda T; Tristram PJ; Vandorou A; Yama H; Albrow MD; Cha S-M; Chung S-J; Gould A; Han C; Hwang K-H; Kim D-J; Kim H-W; Kim S-L; Lee C-U; Lee D-J; Lee Y; Park B-G; Pogge RW; Ryu Y-H; Shin I-G; Shvartzvald Y; Christie G; Cooper T; Drummond J; Green J; Hennerley S; McCormick J; Monard LAG; Natusch T; Porritt I; Tan T-G; Mao S; Maoz D; Penny MT; Zhu W; Bozza V; Cassan A; Dominik M; Hundertmark M; Jaimes RF; Kruszyńska K; Rybicki KA; Street RA; Tsapras Y; Wambsganss J; Wyrzykowski L; Zieliński P; Rau G
    We analyze the MOA-2020-BLG-208 gravitational microlensing event and present the discovery and characterization of a new planet, MOA-2020-BLG-208Lb, with an estimated sub-Saturn mass. With a mass ratio q=3.17-0.26+0.28×10-4, the planet lies near the peak of the mass-ratio function derived by the MOA collaboration and near the edge of expected sample sensitivity. For these estimates we provide results using two mass-law priors: one assuming that all stars have an equal planet-hosting probability, and the other assuming that planets are more likely to orbit around more massive stars. In the first scenario, we estimate that the lens system is likely to be a planet of mass mplanet=46-24+42M⊕ and a host star of mass Mhost=0.43-0.23+0.39M⊙, located at a distance DL=7.49-1.13+0.99kpc . For the second scenario, we estimate mplanet=69-34+37M⊕, Mhost=0.66-0.32+0.35M⊙, and DL=7.81-0.93+0.93kpc . The planet has a projected separation as a fraction of the Einstein ring radius s=1.3807-0.0018+0.0018 . As a cool sub-Saturn-mass planet, this planet adds to a growing collection of evidence for revised planetary formation models