Mon. Not. R. Astron. Soc., 498, 5604-5619 (2020/November-2)
The extreme colliding-wind system Apep: resolved imagery of the central binary and dust plume in the infrared.
HAN Y., TUTHILL P.G., LAU R.M., SOULAIN A., CALLINGHAM J.R., WILLIAMS P.M., CROWTHER P.A., POPE B.J.S. and MARCOTE B.
Abstract (from CDS):
The recent discovery of a spectacular dust plume in the system 2XMM J160050.7-514245 (referred to as 'Apep') suggested a physical origin in a colliding-wind binary by way of the 'Pinwheel' mechanism. Observational data pointed to a hierarchical triple-star system, however, several extreme and unexpected physical properties seem to defy the established physics of such objects. Most notably, a stark discrepancy was found in the observed outflow speed of the gas as measured spectroscopically in the line-of-sight direction compared to the proper motion expansion of the dust in the sky plane. This enigmatic behaviour arises at the wind base within the central Wolf-Rayet binary: a system that has so far remained spatially unresolved. Here, we present an updated proper motion study deriving the expansion speed of Apep's dust plume over a 2-year baseline that is four times slower than the spectroscopic wind speed, confirming and strengthening the previous finding. We also present the results from high angular resolution near-infrared imaging studies of the heart of the system, revealing a close binary with properties matching a Wolf-Rayet colliding-wind system. Based on these new observational constraints, an improved geometric model is presented yielding a close match to the data, constraining the orbital parameters of the Wolf-Rayet binary and lending further support to the anisotropic wind model.
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
techniques: high angular resolution - stars: individual: Apep - stars: Wolf-Rayet
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