A Newly Identified Degeneracy Keeps the Planetary Interpretation Viable for OGLE-2011-BLG-0950
9 affiliations
- 1Tsinghua University
- 2Westlake University
- 3University of Warsaw
- 4Westlake Institute for Advanced Study
- 5University of Warwick
- 6NASA Goddard Space Flight Center
- 7University of Maryland
- 8Max-Planck-Institute for Astronomy
- 9Ohio State University
Abstract
The microlensing event OGLE-2011-BLG-0950 exhibits the well-known “Planet/Binary” degeneracy, in which distinct lens configurations produce similar light curves but imply substantially different mass ratios between the lens components. A previous study rejected the then-known planetary model because its predicted lens-source relative proper motion was inconsistent with that measured from high-resolution imaging, thereby favoring the stellar-binary interpretation. In this work, we identify a new planetary model for this event that arises from a newly identified degeneracy, simultaneously reproducing the observed light curve and remaining consistent with the high-resolution imaging constraint, leaving the “Planet/Binary” degeneracy unresolved once again. Under this planetary interpretation, combining constraints from the light-curve modeling and high-resolution observations yields a lens system consisting of a ∼1 M ⊙ host star orbited by a ∼1.5 M Jup planet, with a projected separation of about 2 or 8 au, subject to the “Close/Wide” degeneracy. Our reanalysis of the color–magnitude diagram further indicates that the source star has unresolved companions that contribute nonnegligible blended light, highlighting the importance of carefully accounting for source and lens companions in future Roman microlensing analyses. Finally, we show that adopting a single mass–luminosity relation significantly underestimates the uncertainties in the inferred lens properties for host masses ≳1 M ⊙ .
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BibTeX
@article{zhang2026newly,
title = {{A Newly Identified Degeneracy Keeps the Planetary Interpretation Viable for OGLE-2011-BLG-0950}},
author = {Jiyuan Zhang and Weicheng Zang and Andrzej Udalski and Hongjing Yang and Shude Mao and Michał K. Szymański and Igor Soszyński and Radoslaw Poleski and Krzysztof Ulaczyk and Paweł Pietrukowicz and Szymon Kozłowski and Jan Skowron and Przemek Mróz and Sean Terry and Andrew Gould},
journal = {The Astronomical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-3881/aea291},
url = {https://iopscience.iop.org/article/10.3847/1538-3881/aea291},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - A Newly Identified Degeneracy Keeps the Planetary Interpretation Viable for OGLE-2011-BLG-0950
AU - Jiyuan Zhang
AU - Weicheng Zang
AU - Andrzej Udalski
AU - Hongjing Yang
AU - Shude Mao
AU - Michał K. Szymański
AU - Igor Soszyński
AU - Radoslaw Poleski
AU - Krzysztof Ulaczyk
AU - Paweł Pietrukowicz
AU - Szymon Kozłowski
AU - Jan Skowron
AU - Przemek Mróz
AU - Sean Terry
AU - Andrew Gould
PY - 2026
DA - 2026/10/01
JO - The Astronomical Journal
DO - 10.3847/1538-3881/aea291
UR - https://iopscience.iop.org/article/10.3847/1538-3881/aea291
AB - The microlensing event OGLE-2011-BLG-0950 exhibits the well-known “Planet/Binary” degeneracy, in which distinct lens configurations produce similar light curves but imply substantially different mass ratios between the lens components. A previous study rejected the then-known planetary model because its predicted lens-source relative proper motion was inconsistent with that measured from high-resolution imaging, thereby favoring the stellar-binary interpretation. In this work, we identify a new planetary model for this event that arises from a newly identified degeneracy, simultaneously reproducing the observed light curve and remaining consistent with the high-resolution imaging constraint, leaving the “Planet/Binary” degeneracy unresolved once again. Under this planetary interpretation, combining constraints from the light-curve modeling and high-resolution observations yields a lens system consisting of a ∼1 M ⊙ host star orbited by a ∼1.5 M Jup planet, with a projected separation of about 2 or 8 au, subject to the “Close/Wide” degeneracy. Our reanalysis of the color–magnitude diagram further indicates that the source star has unresolved companions that contribute nonnegligible blended light, highlighting the importance of carefully accounting for source and lens companions in future Roman microlensing analyses. Finally, we show that adopting a single mass–luminosity relation significantly underestimates the uncertainties in the inferred lens properties for host masses ≳1 M ⊙ .
SN - 0004-6256
SN - 1538-3881
ER -