Constraining lens masses in moderately to highly magnified microlensing events from Gaia

U. Pylypenko; Ł. Wyrzykowski; P. J. Mikołajczyk; K. Kotysz; P. Zieliński; N. Ihanec; M. Wicker; M. Ratajczak; M. Sitek; K. Howil; M. Jabłońska; Z. Kaczmarek; K. Kruszyńska; A. Udalski; G. Damljanovic; M. Stojanovic; M. D. Jovanovic; T. Kvernadze; O. Kvaratskhelia; M. Żejmo; S. M. Brincat; J. K. T. Qvam; T. Güver; E. Bachelet; K. A. Rybicki; A. Garofalo; J. Zdanavicius; E. Pakstiene; S. Zola; S. Kurowski; D. E. Reichart; J. W. Davidson Jr.; U. Burgaz; J. P. Rivet; M. Jelinek; A. Popowicz; H. H. Esenoglu; E. Sonbas; J. M. Carrasco; S. Awiphan; O. Tasuya; V. Godunova; A. Simon; A. Fukui; C. Galdies; K. Bąkowska; P. Hofbauer; A. Gurgul; B. Joachimczyk; M. Dominik; F. Cusano; I. Ilyin; Y. Tsapras; R. A. Street; M. Hundertmark; V. Bozza; P. Rota; A. Cassan; J. Wambsganss; R. Figuera Jaimes

doi:10.1051/0004-6361/202554935

Constraining lens masses in moderately to highly magnified microlensing events from Gaia

U. Pylypenko^*, Ł. Wyrzykowski, P. J. Mikołajczyk, K. Kotysz, P. Zieliński, N. Ihanec, M. Wicker, M. Ratajczak, M. Sitek, K. Howil, M. Jabłońska, Z. Kaczmarek, K. Kruszyńska, A. Udalski, G. Damljanovic, M. Stojanovic, M. D. Jovanovic, T. Kvernadze, O. Kvaratskhelia, M. ŻejmoS. M. Brincat, J. K. T. Qvam, T. Güver, E. Bachelet, K. A. Rybicki, A. Garofalo, J. Zdanavicius, E. Pakstiene, S. Zola, S. Kurowski, D. E. Reichart, J. W. Davidson Jr., U. Burgaz, J. P. Rivet, M. Jelinek, A. Popowicz, H. H. Esenoglu, E. Sonbas, J. M. Carrasco, S. Awiphan, O. Tasuya, V. Godunova, A. Simon, A. Fukui, C. Galdies, K. Bąkowska, P. Hofbauer, A. Gurgul, B. Joachimczyk, M. Dominik, F. Cusano, I. Ilyin, Y. Tsapras, R. A. Street, M. Hundertmark, V. Bozza, P. Rota, A. Cassan, J. Wambsganss, R. Figuera Jaimes

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

Context. Microlensing events provide a unique way to detect and measure the masses of isolated, non-luminous objects, particularly dark stellar remnants. Under certain conditions, it is possible to measure the mass of these objects using photometry alone, specifically when a microlensing light curve displays a finite source (FS) effect. This effect generally occurs in highly magnified light curves, i.e. when the source and the lens are very well aligned.

Aims. In this study, we analyse Gaia Alerts and Gaia Data Release 3 datasets, identifying four moderate-to-high-magnification microlensing events without a discernible FS effect. The absence of this effect suggests a large Einstein radius, implying substantial lens masses.

Methods. In each event, we constrained the FS effect, and therefore established lower limits for the angular Einstein radius and lens mass. Additionally, we used the DarkLensCode software to obtain the mass, distance, and brightness distribution for the lens based on the Galactic model.

Results. Our analysis established lower mass limits of ∼0.7 M_⊙ for one lens and ∼0.3 − 0.5 M_⊙ for two others. A DarkLensCode analysis supports these findings, estimating lens masses in the range of ∼0.42 − 1.70 M_⊙ and dark lens probabilities exceeding 80%. These results strongly indicate that the lenses are stellar remnants, such as white dwarfs or neutron stars.

Conclusions. While further investigations are required to confirm the nature of these lenses, we demonstrate a straightforward yet effective approach to identifying stellar remnant candidates.

Original language	English
Article number	A24
Number of pages	19
Journal	Astronomy & Astrophysics
Volume	705
Early online date	24 Dec 2025
DOIs	https://doi.org/10.1051/0004-6361/202554935
Publication status	Published - 1 Jan 2026

Keywords

Gravitational lensing: micro
Stars: neutron
White dwarfs
Galaxy: general

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Pylypenko_2025_AaA_Constraining-lens-masses-microlensing-Gaia_CC
© The Authors 2025. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Final published version, 2.94 MBLicence: CC BY

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Pylypenko, U., Wyrzykowski, Ł., Mikołajczyk, P. J., Kotysz, K., Zieliński, P., Ihanec, N., Wicker, M., Ratajczak, M., Sitek, M., Howil, K., Jabłońska, M., Kaczmarek, Z., Kruszyńska, K., Udalski, A., Damljanovic, G., Stojanovic, M., Jovanovic, M. D., Kvernadze, T., Kvaratskhelia, O., ... Figuera Jaimes, R. (2026). Constraining lens masses in moderately to highly magnified microlensing events from Gaia. Astronomy & Astrophysics, 705, Article A24. https://doi.org/10.1051/0004-6361/202554935

@article{14e385677dcf456aa129b8f63f7a2bb8,

title = "Constraining lens masses in moderately to highly magnified microlensing events from Gaia",

abstract = "Context. Microlensing events provide a unique way to detect and measure the masses of isolated, non-luminous objects, particularly dark stellar remnants. Under certain conditions, it is possible to measure the mass of these objects using photometry alone, specifically when a microlensing light curve displays a finite source (FS) effect. This effect generally occurs in highly magnified light curves, i.e. when the source and the lens are very well aligned. Aims. In this study, we analyse Gaia Alerts and Gaia Data Release 3 datasets, identifying four moderate-to-high-magnification microlensing events without a discernible FS effect. The absence of this effect suggests a large Einstein radius, implying substantial lens masses. Methods. In each event, we constrained the FS effect, and therefore established lower limits for the angular Einstein radius and lens mass. Additionally, we used the DarkLensCode software to obtain the mass, distance, and brightness distribution for the lens based on the Galactic model. Results. Our analysis established lower mass limits of ∼0.7 M⊙ for one lens and ∼0.3 − 0.5 M⊙ for two others. A DarkLensCode analysis supports these findings, estimating lens masses in the range of ∼0.42 − 1.70 M⊙ and dark lens probabilities exceeding 80\%. These results strongly indicate that the lenses are stellar remnants, such as white dwarfs or neutron stars. Conclusions. While further investigations are required to confirm the nature of these lenses, we demonstrate a straightforward yet effective approach to identifying stellar remnant candidates.",

keywords = "Gravitational lensing: micro, Stars: neutron, White dwarfs, Galaxy: general",

author = "U. Pylypenko and {\L}. Wyrzykowski and Miko{\l}ajczyk, \{P. J.\} and K. Kotysz and P. Zieli{\'n}ski and N. Ihanec and M. Wicker and M. Ratajczak and M. Sitek and K. Howil and M. Jab{\l}o{\'n}ska and Z. Kaczmarek and K. Kruszy{\'n}ska and A. Udalski and G. Damljanovic and M. Stojanovic and Jovanovic, \{M. D.\} and T. Kvernadze and O. Kvaratskhelia and M. {\.Z}ejmo and Brincat, \{S. M.\} and Qvam, \{J. K. T.\} and T. G{\"u}ver and E. Bachelet and Rybicki, \{K. A.\} and A. Garofalo and J. Zdanavicius and E. Pakstiene and S. Zola and S. Kurowski and Reichart, \{D. E.\} and \{Davidson Jr.\}, \{J. W.\} and U. Burgaz and Rivet, \{J. P.\} and M. Jelinek and A. Popowicz and Esenoglu, \{H. H.\} and E. Sonbas and Carrasco, \{J. M.\} and S. Awiphan and O. Tasuya and V. Godunova and A. Simon and A. Fukui and C. Galdies and K. B{\c a}kowska and P. Hofbauer and A. Gurgul and B. Joachimczyk and M. Dominik and F. Cusano and I. Ilyin and Y. Tsapras and Street, \{R. A.\} and M. Hundertmark and V. Bozza and P. Rota and A. Cassan and J. Wambsganss and \{Figuera Jaimes\}, R.",

note = "Funding: This project has received funding from the European Union{\textquoteright}s Horizon Europe Research and Innovation programme ACME under grant agreement No 101131928 (2024-2028). ZTF is supported by the National Science Foundation under Grants No. AST-1440341 and AST-2034437. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. YT acknowledges the support of DFG priority program SPP 1992 {"}Exploring the Diversity of Extrasolar Planets{"} (TS 356/3-1). RAS and EB gratefully acknowledge support from the NASA XRP Program, through grant number 80NSSC19K0291. The Omega Key Project has received funding from the European Union{\textquoteright}s Horizon 2020 research and innovation program under grant agreement No. 101004719 (OPTICON - RadioNet Pilot). This work is supported by the Polish MNiSW grant DIR/WK/2018/12. Josep Manel Carrasco work was (partially) supported by the Spanish MICIN/AEI/10.13039/501100011033 and by ”ERDF A way of making Europe” by the ”European Union” through grant PID2021-122842OB-C21, and the Institute of Cosmos Sciences University of Barcelona (ICCUB, Unidad de Excelencia ”Mar{\'i}a de Maeztu”) through grant CEX2019-000918-M and the project 2021-SGR-00679 GRC de l{\textquoteright}Ag{\`e}ncia de Gesti{\'o} d{\textquoteright}Ajuts Universitaris i de Recerca (Generalitat de Catalunya). G.D., M.S. and M.D.J acknowledge support by the Astronomical Station Vidojevica and the Ministry of Science, Technological Development and Innovation of the Republic of Serbia (MSTDIRS) through contract no. 451-03-136/2025-03/200002 made with Astronomical Observatory (Belgrade), by the EC through project BELISSIMA (call FP7-REGPOT-2010-5, No. 256772), the observing and financial grant support from the Institute of Astronomy and Rozhen NAO BAS through the bilateral SANU-BAN joint research project {"}GAIA astrometry and fast variable astronomical objects{"}, and support by the SANU project F-187. Also, this research was supported by the Science Fund of the Republic of Serbia, grant no. 6775, Urban Observatory of Belgrade - UrbObsBel. T.G. and the IST60 Telescope has been supported by the Scientific Research Projects Coordination Unit of Istanbul University (Project No.: TSG-2023-40046 and FBG-2017-23943) Turkish Republic, Directorate of Presidential Strategy and Budget project, 2016K121370. This work is partially supported by the Fundamental Fund of Thailand Science Research and Innovation (TSRI) through the National Astronomical Research Institute of Thailand (Public Organization) (FFB680072/0269). J.Z. and E.P. acknowledge funding from the Research Council of Lithuania (LMTLT, grant No. S-LL-24-1).",

year = "2026",

month = jan,

day = "1",

doi = "10.1051/0004-6361/202554935",

language = "English",

volume = "705",

journal = "Astronomy \& Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

Pylypenko, U, Wyrzykowski, Ł, Mikołajczyk, PJ, Kotysz, K, Zieliński, P, Ihanec, N, Wicker, M, Ratajczak, M, Sitek, M, Howil, K, Jabłońska, M, Kaczmarek, Z, Kruszyńska, K, Udalski, A, Damljanovic, G, Stojanovic, M, Jovanovic, MD, Kvernadze, T, Kvaratskhelia, O, Żejmo, M, Brincat, SM, Qvam, JKT, Güver, T, Bachelet, E, Rybicki, KA, Garofalo, A, Zdanavicius, J, Pakstiene, E, Zola, S, Kurowski, S, Reichart, DE, Davidson Jr., JW, Burgaz, U, Rivet, JP, Jelinek, M, Popowicz, A, Esenoglu, HH, Sonbas, E, Carrasco, JM, Awiphan, S, Tasuya, O, Godunova, V, Simon, A, Fukui, A, Galdies, C, Bąkowska, K, Hofbauer, P, Gurgul, A, Joachimczyk, B, Dominik, M, Cusano, F, Ilyin, I, Tsapras, Y, Street, RA, Hundertmark, M, Bozza, V, Rota, P, Cassan, A, Wambsganss, J & Figuera Jaimes, R 2026, 'Constraining lens masses in moderately to highly magnified microlensing events from Gaia', Astronomy & Astrophysics, vol. 705, A24. https://doi.org/10.1051/0004-6361/202554935

TY - JOUR

T1 - Constraining lens masses in moderately to highly magnified microlensing events from Gaia

AU - Pylypenko, U.

AU - Wyrzykowski, Ł.

AU - Mikołajczyk, P. J.

AU - Kotysz, K.

AU - Zieliński, P.

AU - Ihanec, N.

AU - Wicker, M.

AU - Ratajczak, M.

AU - Sitek, M.

AU - Howil, K.

AU - Jabłońska, M.

AU - Kaczmarek, Z.

AU - Kruszyńska, K.

AU - Udalski, A.

AU - Damljanovic, G.

AU - Stojanovic, M.

AU - Jovanovic, M. D.

AU - Kvernadze, T.

AU - Kvaratskhelia, O.

AU - Żejmo, M.

AU - Brincat, S. M.

AU - Qvam, J. K. T.

AU - Güver, T.

AU - Bachelet, E.

AU - Rybicki, K. A.

AU - Garofalo, A.

AU - Zdanavicius, J.

AU - Pakstiene, E.

AU - Zola, S.

AU - Kurowski, S.

AU - Reichart, D. E.

AU - Davidson Jr., J. W.

AU - Burgaz, U.

AU - Rivet, J. P.

AU - Jelinek, M.

AU - Popowicz, A.

AU - Esenoglu, H. H.

AU - Sonbas, E.

AU - Carrasco, J. M.

AU - Awiphan, S.

AU - Tasuya, O.

AU - Godunova, V.

AU - Simon, A.

AU - Fukui, A.

AU - Galdies, C.

AU - Bąkowska, K.

AU - Hofbauer, P.

AU - Gurgul, A.

AU - Joachimczyk, B.

AU - Dominik, M.

AU - Cusano, F.

AU - Ilyin, I.

AU - Tsapras, Y.

AU - Street, R. A.

AU - Hundertmark, M.

AU - Bozza, V.

AU - Rota, P.

AU - Cassan, A.

AU - Wambsganss, J.

AU - Figuera Jaimes, R.

N1 - Funding: This project has received funding from the European Union’s Horizon Europe Research and Innovation programme ACME under grant agreement No 101131928 (2024-2028). ZTF is supported by the National Science Foundation under Grants No. AST-1440341 and AST-2034437. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. YT acknowledges the support of DFG priority program SPP 1992 "Exploring the Diversity of Extrasolar Planets" (TS 356/3-1). RAS and EB gratefully acknowledge support from the NASA XRP Program, through grant number 80NSSC19K0291. The Omega Key Project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 101004719 (OPTICON - RadioNet Pilot). This work is supported by the Polish MNiSW grant DIR/WK/2018/12. Josep Manel Carrasco work was (partially) supported by the Spanish MICIN/AEI/10.13039/501100011033 and by ”ERDF A way of making Europe” by the ”European Union” through grant PID2021-122842OB-C21, and the Institute of Cosmos Sciences University of Barcelona (ICCUB, Unidad de Excelencia ”María de Maeztu”) through grant CEX2019-000918-M and the project 2021-SGR-00679 GRC de l’Agència de Gestió d’Ajuts Universitaris i de Recerca (Generalitat de Catalunya). G.D., M.S. and M.D.J acknowledge support by the Astronomical Station Vidojevica and the Ministry of Science, Technological Development and Innovation of the Republic of Serbia (MSTDIRS) through contract no. 451-03-136/2025-03/200002 made with Astronomical Observatory (Belgrade), by the EC through project BELISSIMA (call FP7-REGPOT-2010-5, No. 256772), the observing and financial grant support from the Institute of Astronomy and Rozhen NAO BAS through the bilateral SANU-BAN joint research project "GAIA astrometry and fast variable astronomical objects", and support by the SANU project F-187. Also, this research was supported by the Science Fund of the Republic of Serbia, grant no. 6775, Urban Observatory of Belgrade - UrbObsBel. T.G. and the IST60 Telescope has been supported by the Scientific Research Projects Coordination Unit of Istanbul University (Project No.: TSG-2023-40046 and FBG-2017-23943) Turkish Republic, Directorate of Presidential Strategy and Budget project, 2016K121370. This work is partially supported by the Fundamental Fund of Thailand Science Research and Innovation (TSRI) through the National Astronomical Research Institute of Thailand (Public Organization) (FFB680072/0269). J.Z. and E.P. acknowledge funding from the Research Council of Lithuania (LMTLT, grant No. S-LL-24-1).

PY - 2026/1/1

Y1 - 2026/1/1

N2 - Context. Microlensing events provide a unique way to detect and measure the masses of isolated, non-luminous objects, particularly dark stellar remnants. Under certain conditions, it is possible to measure the mass of these objects using photometry alone, specifically when a microlensing light curve displays a finite source (FS) effect. This effect generally occurs in highly magnified light curves, i.e. when the source and the lens are very well aligned. Aims. In this study, we analyse Gaia Alerts and Gaia Data Release 3 datasets, identifying four moderate-to-high-magnification microlensing events without a discernible FS effect. The absence of this effect suggests a large Einstein radius, implying substantial lens masses. Methods. In each event, we constrained the FS effect, and therefore established lower limits for the angular Einstein radius and lens mass. Additionally, we used the DarkLensCode software to obtain the mass, distance, and brightness distribution for the lens based on the Galactic model. Results. Our analysis established lower mass limits of ∼0.7 M⊙ for one lens and ∼0.3 − 0.5 M⊙ for two others. A DarkLensCode analysis supports these findings, estimating lens masses in the range of ∼0.42 − 1.70 M⊙ and dark lens probabilities exceeding 80%. These results strongly indicate that the lenses are stellar remnants, such as white dwarfs or neutron stars. Conclusions. While further investigations are required to confirm the nature of these lenses, we demonstrate a straightforward yet effective approach to identifying stellar remnant candidates.

AB - Context. Microlensing events provide a unique way to detect and measure the masses of isolated, non-luminous objects, particularly dark stellar remnants. Under certain conditions, it is possible to measure the mass of these objects using photometry alone, specifically when a microlensing light curve displays a finite source (FS) effect. This effect generally occurs in highly magnified light curves, i.e. when the source and the lens are very well aligned. Aims. In this study, we analyse Gaia Alerts and Gaia Data Release 3 datasets, identifying four moderate-to-high-magnification microlensing events without a discernible FS effect. The absence of this effect suggests a large Einstein radius, implying substantial lens masses. Methods. In each event, we constrained the FS effect, and therefore established lower limits for the angular Einstein radius and lens mass. Additionally, we used the DarkLensCode software to obtain the mass, distance, and brightness distribution for the lens based on the Galactic model. Results. Our analysis established lower mass limits of ∼0.7 M⊙ for one lens and ∼0.3 − 0.5 M⊙ for two others. A DarkLensCode analysis supports these findings, estimating lens masses in the range of ∼0.42 − 1.70 M⊙ and dark lens probabilities exceeding 80%. These results strongly indicate that the lenses are stellar remnants, such as white dwarfs or neutron stars. Conclusions. While further investigations are required to confirm the nature of these lenses, we demonstrate a straightforward yet effective approach to identifying stellar remnant candidates.

KW - Gravitational lensing: micro

KW - Stars: neutron

KW - White dwarfs

KW - Galaxy: general

U2 - 10.1051/0004-6361/202554935

DO - 10.1051/0004-6361/202554935

M3 - Article

SN - 0004-6361

VL - 705

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

M1 - A24

ER -

Constraining lens masses in moderately to highly magnified microlensing events from Gaia

Abstract

Keywords

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