A re-establishing jet during an X-ray re-brightening of the Be/X-ray binary Swift J0243.6+6124
Date
03/2019Author
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Abstract
Transient Be/X-ray binary systems, wherein a compact object accretes from a Be-companion star, can show giant and periastron outbursts. During the decay of their giant outbursts, some Be/X-ray binaries also show X-ray re-brightenings, the origin of which is not understood. Recently, we presented the discovery of a jet from a neutron star Be/X-ray binary, observed during the giant outburst of Swift J0243.6+6124. Here, we present continued radio monitoring of its 2017/2018 giant outburst decay and a re-brightening of this source. During the former, we observe a radio flare with a steep radio spectrum, possibly caused by interactions between discrete ejecta colliding with the pre-existing jet or the surrounding medium. During the X-ray re-brightening, we observe the radio jet turning on and off within days. Surprisingly, this re-establishing jet is as bright in radio as at the peak of the super-Eddington giant outburst, despite more than 2 orders of magnitude lower X-ray luminosity. In addition, the jet is only observed when the X-ray luminosity exceeds approximately 2 × 1036 (D/5kpc)2 erg s−1. We discuss how such an X-ray threshold for jet launching might be related to the presence of a magnetic centrifugal barrier at lower mass accretion rates. We also discuss the implications of our results for the launch of jets from strongly magnetized neutron stars, and explore future avenues to exploit the new possibility of coordinated X-ray/radio studies of neutron star Be/X-ray binaries.
Citation
van den Eijnden , J , Degenaar , N , Russell , T D , Hernández Santisteban , J V , Wijnands , R , Miller-Jones , J C A , Rouco Escorial , A & Sivakoff , G R 2019 , ' A re-establishing jet during an X-ray re-brightening of the Be/X-ray binary Swift J0243.6+6124 ' , Monthly Notices of the Royal Astronomical Society , vol. 483 , no. 4 , pp. 4628-4638 . https://doi.org/10.1093/mnras/sty3479
Publication
Monthly Notices of the Royal Astronomical Society
Status
Peer reviewed
ISSN
0035-8711Type
Journal article
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© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the final published version of the work, which was originally published at https://doi.org/10.1093/mnras/sty3479
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