README.md

---
license: cc-by-4.0
pretty_name: "McGill Online Magnetar Catalog"
language:
  - en
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 as"
task_categories:
  - tabular-classification
  - tabular-regression
tags:
  - space
  - magnetars
  - neutron-stars
  - x-ray
  - astronomy
  - open-data
  - tabular-data
  - parquet
size_categories:
  - n<1K
configs:
  - config_name: default
    data_files:
      - split: train
        path: data/mcgill_magnetar_catalog.parquet
    default: true
---

# McGill Online Magnetar Catalog


<div align="center">
  <img src="banner.jpg" alt="Illustration of different types of neutron stars" width="400">
  <p><em>Credit: NASA/JPL-Caltech</em></p>
</div>


*Part of a [dataset collection](https://huggingface.co/collections/juliensimon/astronomy-datasets-67ac2ada12aceb39f8feca3b) 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 = -4*pi^2*I*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

```python
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](https://huggingface.co/datasets/juliensimon/pulsar-catalog)

- [juliensimon/gamma-ray-bursts](https://huggingface.co/datasets/juliensimon/gamma-ray-bursts)

- [juliensimon/fermi-4fgl-dr4](https://huggingface.co/datasets/juliensimon/fermi-4fgl-dr4)

## Citation

```bibtex
@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](https://creativecommons.org/licenses/by/4.0/)