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


Accretion at super-Eddington rates is expected to be accompanied by strong outflows. Such outflows are observed inGalactic 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.


© The Author(s) 2019. cc-by


Accretion, accretion discs, Pulsars: Individual: Swift J0243.6+6124, Stars: neutron, X-rays: Binaries


Van, Den, Eijnden, J., Degenaar, N., Schulz, N.S., Nowak, M.A., Wijnands, R., Russell, T.D., Hernandez, Santisteban, J.V., Bahramian, A., MacCarone, T.J., Kennea, J.A., & Heinke, C.O.. 2019. Chandra reveals a possible ultrafast outflow in the super-Eddington Be/X-ray binary Swift J0243.6+6124. Monthly Notices of the Royal Astronomical Society, 487(3).