juliensimon/chandra-x-ray-sources

Chandra X-Ray Source Catalog

Credit: NASA/DOE/Fermi LAT Collaboration

Part of a dataset collection on Hugging Face.

Dataset description

The Chandra Source Catalog (CSC 2.1) is the definitive catalog of X-ray sources detected by NASA's Chandra X-Ray Observatory, the most powerful X-ray telescope ever built.

The Chandra X-Ray Observatory, launched in 1999, provides the sharpest X-ray images ever achieved, with sub-arcsecond angular resolution. The Chandra Source Catalog is a comprehensive catalog of all X-ray sources detected in Chandra observations, including positions, multi-band photometry (soft, medium, hard, broad, wide bands), hardness ratios for spectral characterization, variability flags, and source extent measurements.

CSC 2.1 covers roughly 560 square degrees of sky and includes sources from over 15,000 individual Chandra observations. The catalog is essential for multi-wavelength studies of active galactic nuclei, X-ray binaries, supernova remnants, galaxy clusters, and stellar coronae.

Chandra's angular resolution of approximately 0.5 arcseconds is achieved by its four nested pairs of grazing-incidence Wolter Type-I mirrors. This resolution makes the Chandra Source Catalog uniquely powerful: it resolves individual X-ray sources in crowded fields such as the Galactic center, globular clusters, and nearby galaxies where other X-ray telescopes would see only confused blends.

Schema

Column	Type	Description	Sample	Null %
row	int64	HEASARC internal row identifier	7978	0.0%
obsid	int64	Chandra observation identifier (unique per pointing)	31425	0.0%
status	string	Observation status: archived, observed, or scheduled	untriggered	0.0%
name	string	Chandra observation target name or source designation	IGR J17480-2446	0.0%
ra	float64	ICRS right ascension in degrees; sub-arcsecond accuracy from Chandra's 0.5" resolution	267.02013	0.2%
dec	float64	ICRS declination in degrees	-24.78024	0.2%
lii	float64	Galactic longitude in degrees	3.83841844	0.2%
bii	float64	Galactic latitude in degrees	1.68626595	0.2%
time	float64	Observation start time	56190.3067361111	1.8%
detector	string	Instrument detector used: ACIS-I, ACIS-S, HRC-I, or HRC-S	ACIS-S	0.0%
grating	string	Grating configuration: NONE, LETG, or HETG	HETG	0.0%
exposure	float64	Exposure time in kiloseconds	200000.0	0.0%
type	string	Observation type: GO (guest observer), GTO (guaranteed time), DDT (director's discretionary), CAL (calibration)	TOO	0.0%
pi	string	Principal investigator last name	Marshall	0.0%
cycle	int64	Chandra observing cycle number (proposal cycle)	27	0.0%
proposal	int64	Proposal title for the observation	27400375	0.0%
public_date	float64	Date when the observation data became publicly available	56576.0	4.4%
sequence_number	int64	Chandra sequence number for the observation	402653	0.0%
data_mode	string	Telemetry mode used (e.g., FAINT, VFAINT, CC33_FAINT)	CC_0012C	0.7%
category	string	Science category assigned to the observation (e.g., AGN, SNR, STARS)	BH AND NS BINARIES	0.0%
x_ra_dec	float64	Unit vector X component of the pointing direction	-0.90669444668946	0.2%
y_ra_dec	float64	Unit vector Y component of the pointing direction	-0.0471984200843957	0.2%
z_ra_dec	float64	Unit vector Z component of the pointing direction	-0.419138985879422	0.2%

Quick stats

• 28,176 Chandra observations in the master catalog
• Median exposure: 15040.0 ks
• Instruments: 4 detector configurations

Usage

from datasets import load_dataset

ds = load_dataset("juliensimon/chandra-x-ray-sources", split="train")
df = ds.to_pandas()

# Longest observations
top = df.nlargest(10, "exposure")[["name", "ra", "dec", "exposure", "detector"]]
print(top.to_string())

# Sky coverage map
import matplotlib.pyplot as plt
fig, ax = plt.subplots(figsize=(12, 6))
ax.scatter(df["ra"], df["dec"], s=0.1, alpha=0.2)
ax.set_xlabel("RA (deg)")
ax.set_ylabel("Dec (deg)")
ax.invert_xaxis()
ax.set_title("Chandra Observation Pointings")
plt.tight_layout()
plt.show()

# Detector usage breakdown
df["detector"].value_counts().plot.bar()
plt.title("Chandra Detector Usage")
plt.show()

Data source

https://cxc.cfa.harvard.edu/csc/

Related datasets

• juliensimon/erosita-erass1-xray

• juliensimon/fermi-4fgl-dr4

• juliensimon/pulsar-catalog

Citation

@dataset{chandra_x_ray_sources,
  title = {Chandra X-Ray Source Catalog},
  author = {juliensimon},
  year = {2026},
  url = {https://huggingface.co/datasets/juliensimon/chandra-x-ray-sources},
  publisher = {Hugging Face}
}

License

CC-BY-4.0