juliensimon/mcgill-magnetar-catalog

McGill Online Magnetar Catalog

Credit: NASA/JPL-Caltech

Part of a dataset collection on Hugging Face.

Dataset description

All known magnetars — neutron stars with extreme magnetic fields (10^13-10^15 G) — from the McGill Online Magnetar Catalog. Includes spin parameters, magnetic field strengths, X-ray properties, and associations.

Magnetars are isolated neutron stars powered by the decay of their ultra-strong magnetic fields, rather than by rotation (like normal pulsars) or accretion. They manifest as Soft Gamma Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs), producing dramatic bursts and flares in X-rays and gamma-rays.

Magnetar magnetic fields — reaching 10^14 to 10^15 Gauss, a thousand times stronger than ordinary pulsars — are the strongest known in the universe. These fields exceed the quantum electrodynamic critical field at which the vacuum itself becomes birefringent. The decay of these colossal fields powers persistent X-ray emission at luminosities of 10^33-36 erg/s, far exceeding what rotational energy alone can supply. During outbursts, magnetars can release up to 10^46 erg in giant flares, rivaling the luminosity of the entire Galaxy.

The magnetar population bridges several areas of astrophysics. Their connection to fast radio bursts (FRBs) was dramatically confirmed in 2020 when SGR 1935+2154 emitted a millisecond radio burst bright enough to be detected at extragalactic distances. Magnetars are also candidate central engines for some gamma-ray bursts and super-luminous supernovae.

Schema

Column	Type	Description	Sample	Null %
name	object	Magnetar designation (e.g. 'SGR 1806-20', '1E 2259+586'); SGR = Soft Gamma Repeater, AXP = Anomalous X-ray Pulsar; both classes are now understood to be magnetars	CXOU J010043.1-721134	0.0%
period_s	float64	Spin period in seconds; magnetars: 2-12 s (far slower than recycled millisecond pulsars); null for sources where timing has not been achieved	8.020392	16.1%
period_err_s	float64	1-sigma uncertainty on spin period (s)	9e-06	16.1%
period_derivative	float64	Spin-down rate dP/dt in s/s; magnetars: ~10^-11 s/s, among the fastest-spinning-down neutron stars; drives inferred magnetic field and characteristic age	1.88e-11	19.4%
period_derivative_err	float64	1-sigma uncertainty on period derivative (s/s)	8e-13	35.5%
magnetic_field_g	float64	Dipole surface magnetic field strength in Gauss, inferred as B ~ 3.2e19 * sqrt(P * Pdot); magnetars: 10^14-10^15 G, roughly 1000x stronger than normal pulsars; null if period or period derivative is unmeasured	393000000000000.0	19.4%
spin_down_luminosity_erg_s	float64	Rotational energy loss rate Edot = -4pi^2I*Pdot/P^3 in erg/s; for magnetars typically 10^32-10^34 erg/s, lower than their observed X-ray luminosity (evidence for magnetic field powering)	1.44e+33	19.4%
characteristic_age_yr	float64	Characteristic spin-down age tau = P/(2*Pdot) in years; magnetars: ~10^3-10^4 yr (very young neutron stars); this is an upper limit on true age for initially fast rotators	6760.0	19.4%
column_density_cm2	float64	Interstellar hydrogen column density N_H in cm^-2, fit from soft X-ray absorption; used to estimate visual extinction and constrain distance; null if no X-ray spectrum available	6.3e+20	29.0%
column_density_err_up	float64	Upper 1-sigma uncertainty on column density (cm^-2)	2e+20	29.0%
column_density_err_down	float64	Lower 1-sigma uncertainty on column density (cm^-2)	1.6e+20	29.0%
photon_index	float64	Photon index Gamma of the hard X-ray power-law spectral component (flux proportional to E^-Gamma); magnetars: Gamma ~ 2-4 in quiescence; null if power-law component not required by the spectrum	3.88	45.2%
photon_index_err_up	float64	Upper 1-sigma uncertainty on photon index	0.01	45.2%
photon_index_err_down	float64	Lower 1-sigma uncertainty on photon index	0.01	45.2%
blackbody_kt_kev	float64	Temperature kT in keV of the soft X-ray blackbody spectral component; magnetars: kT ~ 0.3-0.7 keV; null if spectrum not well-fitted by a blackbody	0.3	45.2%
blackbody_kt_err_up	float64	Upper 1-sigma uncertainty on blackbody kT (keV)	0.02	45.2%
blackbody_kt_err_down	float64	Lower 1-sigma uncertainty on blackbody kT (keV)	0.02	45.2%
xray_flux_erg_cm2_s	float64	Unabsorbed 2-10 keV X-ray flux in erg/cm^2/s from quiescent-state observations; magnetars: ~10^-12-10^-11 erg/cm^2/s; null for transient magnetars in quiescence below detection limits	1.4e-13	19.4%
xray_flux_err_up	float64	Upper 1-sigma uncertainty on X-ray flux (erg/cm^2/s)	1.4e-15	61.3%
xray_flux_err_down	float64	Lower 1-sigma uncertainty on X-ray flux (erg/cm^2/s)	1e-15	61.3%
distance_kpc	float64	Distance in kpc; null for the majority of magnetars (reliable distances are rare — methods include HI absorption, SNR associations, and maser parallaxes)	62.4	19.4%
distance_err_up_kpc	float64	Upper 1-sigma uncertainty on distance (kpc)	1.6	45.2%
distance_err_down_kpc	float64	Lower 1-sigma uncertainty on distance (kpc)	1.6	45.2%
xray_luminosity_erg_s	float64	Quiescent X-ray luminosity in erg/s computed from flux and distance; magnetars: 10^33-10^36 erg/s; null where distance is unknown	6.499999999999999e+34	25.8%
association	object	Name of associated supernova remnant or star cluster (e.g. 'CTB 109', 'Westerlund 1'); null for isolated magnetars without identified associations	SMC	35.5%
optical_ir_counterpart	object	Whether an optical or infrared counterpart has been detected; null if no counterpart search has been published	maybe	0.0%
observed_bands	object	Observational coverage codes: H=hard X-ray (>10 keV), X=soft X-ray, O=optical, I=infrared, R=radio, G=gamma-ray; null if not tabulated	X	9.7%
activity_flags	object	Burst/flare activity type codes: B=bursts, G=giant flare, F=flare, T=transient outburst, A=anti-glitch; null for sources with no recorded activity	BG	9.7%
ra_hms	object	Right ascension in sexagesimal format (HH MM SS.s), ICRS J2000	01 00 43.14	0.0%
ra_err_arcsec	float64	1-sigma positional uncertainty in RA in arcseconds; null for sources without a precise X-ray or radio position	0.13	3.2%
dec_dms	object	Declination in sexagesimal format (+/-DD MM SS.s), ICRS J2000	-72 11 33.8	0.0%
dec_err_arcsec	float64	1-sigma positional uncertainty in Dec in arcseconds; null for sources without a precise X-ray or radio position	0.6	3.2%
is_candidate	bool	True for unconfirmed magnetar candidates (marked with # in the McGill catalog); candidate status may change as new observations are published	False	0.0%
type	object	Historical source class: 'SGR' (detected via gamma-ray bursts) or 'AXP' (detected as anomalous X-ray pulsar); distinction is observational, not physical	AXP	0.0%
ra_deg	float64	Right ascension in decimal degrees (ICRS J2000.0); derived from ra_hms	15.179749999999999	0.0%
dec_deg	float64	Declination in decimal degrees (ICRS J2000.0); derived from dec_dms	-72.19272222222223	0.0%
magnetic_field_g_is_limit	bool	True when the magnetic field value is an upper or lower limit rather than a detection	False	0.0%
spin_down_luminosity_erg_s_is_limit	bool	True when the spin-down luminosity value is an upper or lower limit	False	0.0%
characteristic_age_yr_is_limit	bool	True when the characteristic age value is an upper or lower limit	False	0.0%
xray_flux_erg_cm2_s_is_limit	bool	True when the X-ray flux value is an upper or lower limit	False	0.0%
xray_luminosity_erg_s_is_limit	bool	True when the X-ray luminosity value is an upper or lower limit	False	0.0%
distance_kpc_is_limit	bool	True when the distance value is an upper or lower limit	False	0.0%

Quick stats

• 31 magnetars (24 confirmed, 7 candidates)
• 13 Soft Gamma Repeaters, 18 Anomalous X-ray Pulsars
• 26 with measured spin periods (0.33--11.8 s)
• 25 with inferred magnetic fields (6.10e+12--1.96e+15 G)
• 20 associated with supernova remnants or star clusters

Usage

from datasets import load_dataset

ds = load_dataset("juliensimon/mcgill-magnetar-catalog", split="train")
df = ds.to_pandas()

# Confirmed magnetars only
confirmed = df[~df["is_candidate"]]

# P-Pdot diagram (period vs. period derivative)
import matplotlib.pyplot as plt
import numpy as np

valid = confirmed.dropna(subset=["period_s", "period_derivative"])
plt.figure(figsize=(8, 6))
plt.scatter(valid["period_s"], valid["period_derivative"], s=50, c="crimson", edgecolors="k")
plt.xscale("log")
plt.yscale("log")
plt.xlabel("Spin Period (s)")
plt.ylabel("Period Derivative (s/s)")
plt.title("Magnetar P-Pdot Diagram")
plt.tight_layout()
plt.show()

# Strongest magnetic fields
strongest = confirmed.sort_values("magnetic_field_g", ascending=False).head(5)
print(strongest[["name", "type", "magnetic_field_g", "period_s"]])

Data source

http://www.physics.mcgill.ca/~pulsar/magnetar/main.html

Related datasets

• juliensimon/pulsar-catalog

• juliensimon/gamma-ray-bursts

• juliensimon/fermi-4fgl-dr4

Citation

@dataset{mcgill_magnetar_catalog,
  title = {McGill Online Magnetar Catalog},
  author = {juliensimon},
  year = {2026},
  url = {https://huggingface.co/datasets/juliensimon/mcgill-magnetar-catalog},
  publisher = {Hugging Face}
}

License

CC-BY-4.0