A Changing Wind Collision

作者：Naze Yael^*; Koenig**erger Gloria; Pittard Julian M; Parkin Elliot Ross; Rauw Gregor; Corcoran Michael F; Hillier D John

来源：Astrophysical Journal, 2018, 853(2): 164.

DOI：10.3847/1538-4357/aaa29c

• stars: binaries: eclipsing
• stars: early-type
• stars: winds, outflows
• stars: Wolf-Rayet
• X-rays: stars

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 similar to 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.

• 出版日期2018-2-1