Astrophys. J., 853, 164-164 (2018/February-1)
A changing wind collision.
NAZE Y., KOENIGSBERGER G., PITTARD J.M., PARKIN E.R., RAUW G., CORCORAN M.F. and HILLIER D.J.
Abstract (from CDS):
We report on the first detection of a global change in the X-ray emitting properties of a wind-wind collision, thanks to XMM-Newton observations of the massive Small Magellenic Cloud (SMC) system HD 5980. While its light curve had remained unchanged between 2000 and 2005, the X-ray flux has now increased by a factor of ∼2.5, and slightly hardened. The new observations also extend the observational coverage over the entire orbit, pinpointing the light-curve shape. It has not varied much despite the large overall brightening, and a tight correlation of fluxes with orbital separation is found without any hysteresis effect. Moreover, the absence of eclipses and of absorption effects related to orientation suggests a large size for the X-ray emitting region. Simple analytical models of the wind-wind collision, considering the varying wind properties of the eruptive component in HD 5980, are able to reproduce the recent hardening and the flux-separation relationship, at least qualitatively, but they predict a hardening at apastron and little change in mean flux, contrary to observations. The brightness change could then possibly be related to a recently theorized phenomenon linked to the varying strength of thin-shell instabilities in shocked wind regions.
© 2018. The American Astronomical Society. All rights reserved.
stars: binaries: eclipsing - stars: early-type - stars: winds, outflows - stars: Wolf-Rayet - X-rays: stars - X-rays: stars
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