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| Natura: | Preprint |
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2025
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| Accesso online: | https://arxiv.org/abs/2510.16098 |
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| _version_ | 1866909854211244032 |
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| author | Zhang, Zhoujian Li, Yanxia |
| author_facet | Zhang, Zhoujian Li, Yanxia |
| contents | We present the Ultracool dwarf Science with MachIne LEarning (USMILE), a program developing machine-learning tools for the discovery and characterization of ultracool dwarfs. We introduce USMILE Avocado, a spectral classification framework that uses broadband photometry from wide-field surveys -- Rubin Observatory LSST Data Preview 1, VISTA Hemisphere Survey, and CatWISE -- as input features. The framework has two gradient-boosted decision-tree models scalable to the massive data volumes of modern surveys: the classifier, which distinguishes ultracool dwarfs from stellar/extragalactic contaminants, and the regressor, which predicts spectral types. A key strength is its ability to natively handle missing photometric features, whereas earlier machine-learning approaches required complete multi-band detections or relied on imputation, thereby excluding genuine ultracool dwarfs or introducing bias. Trained on an augmented labeled dataset of >2 million sources built from known ultracool dwarfs, reddened early-type stars, and quasars, the models achieve strong performance: the classifier attains an ROC AUC of 0.976 and an F1 score of 0.92, while the regressor yields a mean-squared error of 0.88 subtypes. Applying these models, we carried out the first ultracool dwarf search with LSST DP1, cross-matched against VHS and CatWISE. Crucially, Euclid Quick Data Release 1 provided near-IR spectra for hundreds of candidates, enabling a rare, large-scale external spectroscopic validation. This confirmed 15 M6--L2 discoveries, verified USMILE performance, and clarified regimes where USMILE predictions are most reliable. Building on these insights, we identified 25 additional M6--L9 photometric candidates. These demonstrate the effectiveness of machine-learning methods in the data-rich era of wide-field surveys, highlighting the synergy between LSST and Euclid in expanding the ultracool dwarf census. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_16098 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Ultracool dwarf Science with MachIne LEarning (USMILE). I. Scalable Tree-Based Models for Photometric Spectral Classification and New Discoveries from LSST Data Preview 1 and Euclid Quick Data Release 1 Zhang, Zhoujian Li, Yanxia Solar and Stellar Astrophysics We present the Ultracool dwarf Science with MachIne LEarning (USMILE), a program developing machine-learning tools for the discovery and characterization of ultracool dwarfs. We introduce USMILE Avocado, a spectral classification framework that uses broadband photometry from wide-field surveys -- Rubin Observatory LSST Data Preview 1, VISTA Hemisphere Survey, and CatWISE -- as input features. The framework has two gradient-boosted decision-tree models scalable to the massive data volumes of modern surveys: the classifier, which distinguishes ultracool dwarfs from stellar/extragalactic contaminants, and the regressor, which predicts spectral types. A key strength is its ability to natively handle missing photometric features, whereas earlier machine-learning approaches required complete multi-band detections or relied on imputation, thereby excluding genuine ultracool dwarfs or introducing bias. Trained on an augmented labeled dataset of >2 million sources built from known ultracool dwarfs, reddened early-type stars, and quasars, the models achieve strong performance: the classifier attains an ROC AUC of 0.976 and an F1 score of 0.92, while the regressor yields a mean-squared error of 0.88 subtypes. Applying these models, we carried out the first ultracool dwarf search with LSST DP1, cross-matched against VHS and CatWISE. Crucially, Euclid Quick Data Release 1 provided near-IR spectra for hundreds of candidates, enabling a rare, large-scale external spectroscopic validation. This confirmed 15 M6--L2 discoveries, verified USMILE performance, and clarified regimes where USMILE predictions are most reliable. Building on these insights, we identified 25 additional M6--L9 photometric candidates. These demonstrate the effectiveness of machine-learning methods in the data-rich era of wide-field surveys, highlighting the synergy between LSST and Euclid in expanding the ultracool dwarf census. |
| title | Ultracool dwarf Science with MachIne LEarning (USMILE). I. Scalable Tree-Based Models for Photometric Spectral Classification and New Discoveries from LSST Data Preview 1 and Euclid Quick Data Release 1 |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2510.16098 |