An evolving jet from a strongly magnetized accreting X-ray pulsar


Relativistic jets are observed throughout the Universe and strongly affect their surrounding environments on a range of physical scales, from Galactic binary systems1 to galaxies and clusters of galaxies2. All types of accreting black hole and neutron star have been observed to launch jets3, with the exception of neutron stars with strong magnetic fields4,5 (higher than 1012 gauss), leading to the conclusion that their magnetic field strength inhibits jet formation6. However, radio emission recently detected from two such objects could have a jet origin, among other possible explanations7,8, indicating that this long-standing idea might need to be reconsidered. But definitive observational evidence of such jets is still lacking. Here we report observations of an evolving jet launched by a strongly magnetized neutron star accreting above the theoretical maximum rate given by the Eddington limit. The radio luminosity of the jet is two orders of magnitude fainter than those seen in other neutron stars with similar X-ray luminosities9, implying an important role for the properties of the neutron star in regulating jet power. Our result also shows that the strong magnetic fields of ultra-luminous X-ray pulsars do not prevent such sources from launching jets.

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Fig. 1: Radio and X-ray outburst light curve of Sw J0243.
Fig. 2: VLA detection images of Sw J0243.
Fig. 3: Radio and X-ray luminosities for X-ray binaries.

Data availability

The VLA observations analysed in this work will become publicly available in the NRAO Science Data Archive ( on 8 November 2018 (first two epochs) and 20 February 2019 (remaining epochs), under project codes 17B-406 and 17B-420, respectively. However, prior access to the VLA observations will be granted by the corresponding author upon reasonable request. All Swift X-ray data are accessible in the HEASARC data archive. The radio–X-ray correlation data sample is available online at


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We thank the VLA for rapidly accepting our proposal and performing the Director’s Discretionary Time (DDT) radio observations, and E. Gallo for providing the black hole sample used in Fig. 3. J.v.d.E., N.D. and J.V.H.S. appreciate support from a Netherlands Organisation for Scientific Research (NWO) Vidi grant awarded to N.D. T.D.R. is supported by an NWO Veni grant. R.W. is supported by an NWO Top grant. J.C.A.M.-J. is supported by an Australian Research Council Future Fellowship (FT140101082). G.R.S. acknowledges support from an NSERC Discovery grant. This work used data supplied by the UK Swift Science Data Centre at the University of Leicester. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work used data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by the national institutions participating in the Gaia Multilateral Agreement.

Reviewer information

Nature thanks R. Fender and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author information




J.v.d.E. led the two VLA DDT observing campaigns, performed the analysis of the Swift data and wrote the manuscript, with comments from all authors. J.v.d.E., N.D. and T.D.R. designed the radio monitoring strategy. T.D.R. and J.v.d.E. jointly analysed the VLA radio data. J.V.H.S. calculated the Gaia DR2 distance estimate. All authors made contributions to the scientific case and commented on multiple versions of the manuscript.

Corresponding author

Correspondence to J. van den Eijnden.

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Extended data figures and tables

Extended Data Fig. 1 Marginal posterior distributions for the distance to Sw J0243.

We show the distribution for an exponential and a uniform prior. The median value (50th percentile) of the distribution for the exponential prior is shown as the dot-dashed line. L is the scale parameter of the exponential prior and rlim is the maximum distance in the uniform prior. PDF, probability density function.

Extended Data Table 1 Overview of VLA radio observations of Sw J0243
Extended Data Table 2 VLA radio flux density, polarization and position measurements
Extended Data Table 3 Swift-XRT flux measurements
Extended Data Table 4 Swift-XRT spectral fit parameters

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van den Eijnden, J., Degenaar, N., Russell, T.D. et al. An evolving jet from a strongly magnetized accreting X-ray pulsar. Nature 562, 233–235 (2018).

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  • Neutron Star
  • Radio Luminosity
  • Radio Emission
  • Magnetospheric Radius
  • Leakage Calibration

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