Chandra reveals a possible ultrafast outflow in the super-Eddington Be/X-ray binary Swift J0243.6+6124

J. van den Eijnden, N. Degenaar, N. S. Schulz, M. A. Nowak, R. Wijnands, T. D. Russell, J. V. Hernández Santisteban, A. Bahramian, T. J. Maccarone, J. A. Kennea, C. O. Heinke

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7 Citations (Scopus)


Accretion at super-Eddington rates is expected to be accompanied by strong outflows. Such outflows are observed in Galactic X-ray binaries and extragalactic ultraluminous X-ray sources (ULXs). However, due to their large source distances, ULX outflows are challenging to detect and study in detail. Galactic neutron stars accreting from a Be-star companion at super-Eddington rates show many similarities to ULX pulsars, and therefore offer an alternative approach to study outflows in this accretion regime. Here, we present Chandra high-resolution spectroscopy of such a super-Eddington accreting neutron star, Swift J0243.6+6124, to search for wind outflow signatures during the peak of its 2017/2018 giant outburst. We detect narrow emission features at rest from Ne, Mg, S, Si, and Fe. In addition, we detect a collection of absorption features which can be identified in two ways: either as all Fe transitions at rest (with a possible contribution from Mg), or a combination of three blue-shifted Ne and Mg lines at ∼0.22c, while the remaining lines are at rest. The second scenario would imply an outflow with a velocity similar to those seen in ULXs, including the ULX pulsar NGC 300 ULX-1. This result would also imply that Swift J0243.6+6124 launches both a jet, detected in radio and reported previously, and an ultrafast wind outflow simultaneously at super-Eddington accretion rates.
Original languageEnglish
Pages (from-to)4355-4371
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date6 Jun 2019
Publication statusPublished - Aug 2019


  • Accretion
  • Accretion discs
  • Stars: neutron
  • Pulsars: individual: Swift J0243.6+6124
  • X-rays: binaries


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