juliensimon/hot-subdwarf-stars
Hot Subdwarf Star Catalog Credit: NASA/ESA/Hubble Part of a dataset collection on Hugging Face. Dataset description The Catalogue of Hot Subdwarf Stars (Kilkenny, Heber & Drilling 1988), retrieved from VizieR III/137. The compendium remains the historical reference for the population of spectroscopically identified subdwarf B (sdB) and subdwarf O (sdO) stars — evolved low-mass stars that occupy the extreme horizontal branch of the Hertzsprung-Russell… See the full description on the dataset page: https://huggingface.co/datasets/juliensimon/hot-subdwarf-stars.
Hot Subdwarf Star Catalog
<div align="center"> <img src="banner.jpg" alt="A youthful globular star cluster observed by the Hubble Space Telescope" width="400"> <p><em>Credit: NASA/ESA/Hubble</em></p> </div>
Part of a [dataset collection](https://huggingface.co/collections/juliensimon/stellar-catalogs-69c792b1a52ab2757b0eaa57) on Hugging Face.
Dataset description
The Catalogue of Hot Subdwarf Stars (Kilkenny, Heber & Drilling 1988), retrieved from VizieR III/137. The compendium remains the historical reference for the population of spectroscopically identified subdwarf B (sdB) and subdwarf O (sdO) stars — evolved low-mass stars that occupy the extreme horizontal branch of the Hertzsprung-Russell diagram.
Hot subdwarfs are believed to be the bare helium-burning cores of red giants that lost almost all of their hydrogen envelopes near the tip of the giant branch. The dominant formation channel is binary interaction (Roche-lobe overflow or common-envelope ejection), making sdB stars a key laboratory for testing binary stellar evolution theory and the origin of single hot subdwarfs via mergers. They are also major contributors to the ultraviolet excess (UV upturn) observed in elliptical galaxies. Each entry in this catalog records the J2000 sky position, primary designation, V-band photometry, color indices, spectral classification, and the atmospheric parameters effective temperature and surface gravity (log g) when available.
This dataset complements juliensimon/gaia-dr3-white-dwarfs (the post-AGB end-state into which some hot subdwarfs evolve), juliensimon/cataclysmic-variable-catalog and juliensimon/xray-binary-catalog (compact binary systems formed by similar evolutionary pathways), and juliensimon/brown-dwarf-catalog and juliensimon/cns5-nearby-stars for broader stellar-population context.
This dataset is suitable for tabular classification tasks.
Schema
Quick stats
- 1,714 spectroscopically identified hot subdwarf stars
- 770 sdB-type + 470 sdO-type entries
- 22 composite-spectrum binaries (e.g. sdB+F, sdO+K)
- Effective temperatures span 3 to 5 K
- Surface gravities (log g) cluster between 3.30 and 7.00 cgs
Usage
from datasets import load_dataset
ds = load_dataset("juliensimon/hot-subdwarf-stars", split="train")
df = ds.to_pandas()from datasets import load_dataset
import matplotlib.pyplot as plt
df = load_dataset("juliensimon/hot-subdwarf-stars", split="train").to_pandas()
# Kiel diagram (Teff vs log g) — the standard plane for hot subdwarf analysis
mask = df["effective_temperature_k"].notna() & df["log_g"].notna()
fig, ax = plt.subplots(figsize=(8, 6))
ax.scatter(df.loc[mask, "effective_temperature_k"], df.loc[mask, "log_g"],
c=df.loc[mask, "v_magnitude"], s=30, cmap="viridis_r")
ax.invert_xaxis() # hot on the left
ax.invert_yaxis() # large gravity on the bottom
ax.set_xscale("log")
ax.set_xlabel("Effective temperature (K)")
ax.set_ylabel("log g (cgs)")
ax.set_title("Kiel diagram of hot subdwarfs — sdB cluster vs sdO tail")
plt.tight_layout()
plt.show()
# Spectral-type breakdown
print(df["spectral_type"].value_counts().head(20))Data source
https://cdsarc.cds.unistra.fr/viz-bin/cat/III/137
Related datasets
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About the author
Created by Julien Simon — AI Operating Partner at Fortino Capital. Part of the Space Datasets collection.
Citation
@dataset{hot_subdwarf_stars,
title = {Hot Subdwarf Star Catalog},
author = {Simon, Julien},
year = {2026},
url = {https://huggingface.co/datasets/juliensimon/hot-subdwarf-stars},
publisher = {Hugging Face},
note = {Derived from CDS Archive, Centre de Données astronomiques de Strasbourg, https://cdsarc.cds.unistra.fr/viz-bin/cat/III/137}
}