MOA-2010-BLG-328: Keck and HST Expose the Limits of Occams Razor in Microlensing
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arXiv
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| Autores principales: | , , , , , , , , , |
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| Formato: | Preprint |
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2025
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| author | Vandorou, Aikaterini Bennett, David P. Beaulieu, Jean-Philippe Bhattacharya, Aparna Blackman, Joshua W. Cole, Andrew A. Koshimoto, Naoki Ranc, Clément Rektsini, Natalia E. Terry, Sean K. |
| author_facet | Vandorou, Aikaterini Bennett, David P. Beaulieu, Jean-Philippe Bhattacharya, Aparna Blackman, Joshua W. Cole, Andrew A. Koshimoto, Naoki Ranc, Clément Rektsini, Natalia E. Terry, Sean K. |
| contents | We present high resolution follow-up data of the planetary microlensing event MOA-2010-BLG-328, using Keck and the Hubble. Keck data, taken 8 years after the event, reveal a strong lens detection enabling a direct measurement of lens flux and source-lens relative proper motion. We find the relative source-lens proper motion to be $μ_{\rm rel, Hel} = 4.07 \pm 0.34\ \rm mas\ yr^{-1}$, with the lens being $\sim10$ times fainter than the source. The lens was very faint in the Hubble passbands, and the small lens-source separation of $\sim$35 mas made its detection difficult. However, we obtained estimates of the lens magnitudes in Hubble bands by constraining its location to match the Keck K-band detection. The original analysis by \citet{Furusawa2013} reports a degenerate light curve, with several viable models depending on higher-order effects. We attempt to break the degeneracy by remodeling the event using constraints from follow-up data. Our best fit model includes parallax, orbital motion, xallarap and the magnification of a source companion. Models omitting any of these are excluded. However, even with a lens detection the solution remains unclear, as the degeneracy between a nearby late M dwarf and a distant early M dwarf in the disk persists, and cannot be broken with NIR data alone. We conclude the lens is either a $\sim0.2\ M_{\odot}$ star at $2-3$kpc, or a $\sim0.5\ M_{\odot}$ star at $4-5$kpc. This study highlights the importance of multi-band data and comprehensive modeling to resolve microlensing degeneracies. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2504_06347 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | MOA-2010-BLG-328: Keck and HST Expose the Limits of Occams Razor in Microlensing Vandorou, Aikaterini Bennett, David P. Beaulieu, Jean-Philippe Bhattacharya, Aparna Blackman, Joshua W. Cole, Andrew A. Koshimoto, Naoki Ranc, Clément Rektsini, Natalia E. Terry, Sean K. Earth and Planetary Astrophysics Astrophysics of Galaxies Instrumentation and Methods for Astrophysics We present high resolution follow-up data of the planetary microlensing event MOA-2010-BLG-328, using Keck and the Hubble. Keck data, taken 8 years after the event, reveal a strong lens detection enabling a direct measurement of lens flux and source-lens relative proper motion. We find the relative source-lens proper motion to be $μ_{\rm rel, Hel} = 4.07 \pm 0.34\ \rm mas\ yr^{-1}$, with the lens being $\sim10$ times fainter than the source. The lens was very faint in the Hubble passbands, and the small lens-source separation of $\sim$35 mas made its detection difficult. However, we obtained estimates of the lens magnitudes in Hubble bands by constraining its location to match the Keck K-band detection. The original analysis by \citet{Furusawa2013} reports a degenerate light curve, with several viable models depending on higher-order effects. We attempt to break the degeneracy by remodeling the event using constraints from follow-up data. Our best fit model includes parallax, orbital motion, xallarap and the magnification of a source companion. Models omitting any of these are excluded. However, even with a lens detection the solution remains unclear, as the degeneracy between a nearby late M dwarf and a distant early M dwarf in the disk persists, and cannot be broken with NIR data alone. We conclude the lens is either a $\sim0.2\ M_{\odot}$ star at $2-3$kpc, or a $\sim0.5\ M_{\odot}$ star at $4-5$kpc. This study highlights the importance of multi-band data and comprehensive modeling to resolve microlensing degeneracies. |
| title | MOA-2010-BLG-328: Keck and HST Expose the Limits of Occams Razor in Microlensing |
| topic | Earth and Planetary Astrophysics Astrophysics of Galaxies Instrumentation and Methods for Astrophysics |
| url | https://arxiv.org/abs/2504.06347 |