juliensimon/swift-bat-hard-xray-survey

Swift-BAT 157-Month Hard X-Ray Survey

Credit: NASA/JPL-Caltech/STScI/CXC/SAO

Part of a dataset collection on Hugging Face.

Dataset description

Catalog of hard X-ray sources detected in the 14–195 keV band by the Swift Burst Alert Telescope (BAT) over 157 months of all-sky survey observations. The survey represents over 13 years of continuous monitoring of the hard X-ray sky, providing positions, fluxes, and spectral parameters for AGN, X-ray binaries, galaxy clusters, and other high-energy sources sourced from NASA HEASARC.

The Swift-BAT hard X-ray survey is the most sensitive and uniform survey of the sky in the 14–195 keV energy band. BAT is a coded-aperture instrument aboard the Neil Gehrels Swift Observatory that continuously monitors the hard X-ray sky. The 157-month catalog reaches a sensitivity of approximately 8×10⁻¹² erg/cm²/s over most of the sky, probing the hard X-ray luminosity function down to Seyfert-level AGN in the local universe.

Hard X-rays penetrate gas and dust that absorb softer X-rays, making BAT uniquely suited for finding obscured AGN and mapping the local hard X-ray universe. The source population is dominated by active galactic nuclei — both unobscured (Seyfert 1) and obscured (Seyfert 2) — because the 14–195 keV band penetrates Compton-thin absorption (column densities up to N_H ~ 10²⁴ cm⁻²). The BAT AGN sample has been foundational for measuring the intrinsic fraction of obscured AGN as a function of luminosity and redshift, directly constraining models of AGN unification and the cosmic X-ray background.

The spectral parameters — photon indices and fluxes — derived from the time-averaged BAT spectra provide a clean, absorption-independent measure of intrinsic source luminosity. Combined with redshifts, these yield hard X-ray luminosities that anchor the X-ray luminosity function of AGN, a fundamental input to models of supermassive black hole growth and the synthesis of the cosmic X-ray background.

Schema

Column	Type	Description	Sample	Null %
source_number	int64	Sequential source number in the BAT 157-month catalog	287	0.0%
name	object	BAT source designation	SWIFT J0534.6+2204	0.0%
ra	float64	Right ascension in decimal degrees (J2000)	83.6317	0.0%
dec	float64	Declination in decimal degrees (J2000)	22.0168	0.0%
lii	float64	Galactic longitude in degrees	184.55480665	0.0%
bii	float64	Galactic latitude in degrees	-5.78421165	0.0%
snr	float64	Signal-to-noise ratio of the hard X-ray detection in the 14-195 keV band	11484.17	0.0%
ctrpart_name	object	Name of the multi-wavelength counterpart identification	Crab	9.7%
ctrpart_ra	float64	Right ascension of the counterpart (J2000, degrees)	83.6332	10.0%
ctrpart_dec	float64	Declination of the counterpart (J2000, degrees)	22.0145	10.0%
flux	float64	Time-averaged flux in the 14-195 keV band (erg/cm²/s)	2.38615e-08	0.2%
flux_lower	float64	Lower 1-sigma uncertainty on the 14-195 keV flux (erg/cm²/s)	2.38578e-08	0.2%
flux_upper	float64	Upper 1-sigma uncertainty on the 14-195 keV flux (erg/cm²/s)	2.38653e-08	0.0%
spectral_index	float64	Photon spectral index Γ from power-law fit to the BAT spectrum	2.15	0.1%
spectral_index_lower	float64	Lower 1-sigma uncertainty on the photon spectral index	2.15	0.2%
spectral_index_upper	float64	Upper 1-sigma uncertainty on the photon spectral index	2.15	0.2%
chi_squared	float64	Reduced chi-squared of the spectral fit	0.0	0.1%
redshift	float64	Source redshift; null for Galactic sources and unidentified sources	0.0018	41.9%
log_lx	float64	Log10 of the hard X-ray luminosity (erg/s); null if no redshift	42.94	36.4%
ctrpart_flag	int64	Counterpart identification flag (0=no counterpart, 1=associated)	1	0.0%
ctrpart_class	float64	Counterpart classification code	10.0	0.1%
source_type	object	Source classification (e.g., AGN, Sy1, Sy2, XRB, CV, cluster)	Pulsar	0.0%
root_filename	object	Root name of the BAT source file used in the analysis	swbj0534_6p2204_	0.0%

Quick stats

• 1,891 hard X-ray sources detected in the 14–195 keV band
• 1,098 sources with measured redshifts (58% of total)
• 1,213 active galactic nuclei (AGN/Seyfert sources)
• 1,708 sources with multi-wavelength counterpart identifications
• Median detection SNR: 7.2
• Survey coverage: 157 months (~13 years) of Swift BAT all-sky monitoring

Usage

from datasets import load_dataset
import matplotlib.pyplot as plt
import numpy as np

ds = load_dataset("juliensimon/swift-bat-hard-xray-survey", split="train")
df = ds.to_pandas()

# All-sky Mollweide map of hard X-ray sources
fig = plt.figure(figsize=(12, 6))
ax = fig.add_subplot(111, projection="mollweide")
ra_rad = np.deg2rad(df["ra"] - 180)
dec_rad = np.deg2rad(df["dec"])
scatter = ax.scatter(ra_rad, dec_rad, c=np.log10(df["snr"].clip(lower=0.1)),
                     s=3, alpha=0.6, cmap="plasma")
plt.colorbar(scatter, ax=ax, label="log10(SNR)")
ax.set_title("Swift-BAT Hard X-Ray Sources (14-195 keV)")
ax.grid(True)
plt.tight_layout()
plt.savefig("swift_bat_skymap.png", dpi=150)
plt.show()

# Top 10 brightest sources
top10 = df.nlargest(10, "snr")[["name", "snr", "flux", "source_type", "redshift"]]
print("\nTop 10 brightest hard X-ray sources:")
print(top10.to_string(index=False))

# Photon index distribution for AGN
agn = df[df["source_type"].str.contains("Sy|AGN", case=False, na=False)]
plt.figure(figsize=(8, 4))
agn["spectral_index"].dropna().hist(bins=40, edgecolor="k")
plt.xlabel("Photon Index Γ")
plt.ylabel("Count")
plt.title(f"Photon Index Distribution for {len(agn):,} BAT AGN")
plt.tight_layout()
plt.show()

Data source

https://heasarc.gsfc.nasa.gov/xamin/vo/tap/

Related datasets

• juliensimon/gamma-ray-bursts

• juliensimon/pulsar-catalog

• juliensimon/erosita-erass1-xray

Citation

@dataset{swift_bat_hard_xray_survey,
  title = {Swift-BAT 157-Month Hard X-Ray Survey},
  author = {juliensimon},
  year = {2026},
  url = {https://huggingface.co/datasets/juliensimon/swift-bat-hard-xray-survey},
  publisher = {Hugging Face}
}

License

CC-BY-4.0