Update brown dwarf catalog: 14,168 dwarfs

README.md

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+---
+license: cc-by-4.0
+pretty_name: "Ultracool and Brown Dwarf Catalog (40 pc)"
+language:
+  - en
+description: "Ultracool and brown dwarf catalog within 40 pc. JWST-relevant. Sourced via VizieR CDS Strasbourg."
+task_categories:
+  - tabular-classification
+tags:
+  - space
+  - brown-dwarf
+  - ultracool
+  - jwst
+  - stellar
+  - astronomy
+  - open-data
+size_categories:
+  - 10K<n<100K
+---
+
+# Ultracool and Brown Dwarf Catalog (40 pc)
+
+Comprehensive catalog of **14,168** ultracool and brown dwarfs within 40 parsecs,
+highly relevant for JWST atmospheric characterization studies.
+
+## Dataset description
+
+Brown dwarfs are substellar objects too low in mass to sustain hydrogen fusion. Ultracool
+dwarfs (spectral types M7 and later) bridge the gap between the lowest-mass stars and
+giant planets. This volume-complete 40 pc sample from Sebastian et al. (2021) provides
+the most comprehensive census of the solar neighborhood's ultracool population, including
+L, T, and Y dwarfs ideal for JWST follow-up.
+
+## Quick stats
+
+- **14,168** ultracool dwarfs within 40 pc
+- **14,168** with spectral type classification
+- **14,168** with distance estimates
+
+## Usage
+
+```python
+from datasets import load_dataset
+
+ds = load_dataset("juliensimon/brown-dwarf-catalog", split="train")
+df = ds.to_pandas()
+
+# T and Y dwarfs (coldest brown dwarfs)
+if "spectral_type" in df.columns:
+    cold = df[df["spectral_type"].str.startswith(("T", "Y"), na=False)]
+    print(f"{len(cold):,} T/Y dwarfs")
+
+# Nearest brown dwarfs
+if "distance_pc" in df.columns:
+    nearby = df.dropna(subset=["distance_pc"]).sort_values("distance_pc").head(20)
+    print(nearby[["ra_deg", "dec_deg", "distance_pc"]].to_string())
+```
+
+## Data source
+
+Sebastian, D. et al. (2021), "The census of the solar neighbourhood ultracool dwarf
+volume-complete 40 pc sample", A&A, 645, A100. Accessed via
+[VizieR](https://vizier.cds.unistra.fr/), CDS Strasbourg.
+
+## Pipeline
+
+Source code: [juliensimon/space-datasets](https://github.com/juliensimon/space-datasets)
+
+## License
+
+[CC-BY-4.0](https://creativecommons.org/licenses/by/4.0/)

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