期刊
ASTROPHYSICAL JOURNAL
卷 726, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/726/2/105
关键词
hydrodynamics; stars: early-type; stars: individual (eta Carinae); stars: massive; stars: winds, outflows; X-rays: stars
资金
- University of Leeds
- PRODEX XMM/Integral contract (Belspo)
- Royal Society
- University of Chicago
- STFC [ST/H008802/1, ST/I001557/1, ST/F002092/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/F002092/1, ST/H008802/1, ST/I001557/1] Funding Source: researchfish
Three-dimensional adaptive mesh refinement hydrodynamical simulations of the wind-wind collision between the enigmatic supermassive star eta Car and its mysterious companion star are presented which include radiative driving of the stellar winds, gravity, optically thin radiative cooling, and orbital motion. Simulations with static stars with a periastron passage separation reveal that the preshock companion star's wind speed is sufficiently reduced so that radiative cooling in the postshock gas becomes important, permitting the runaway growth of nonlinear thin-shell instabilities (NTSIs) which massively distort the wind-wind collision region (WCR). However, large-scale simulations, which include the orbital motion of the stars, show that orbital motion reduces the impact of radiative inhibition and thus increases the acquired preshock velocities. As such, the postshock gas temperature and cooling time see a commensurate increase, and sufficient gas pressure is preserved to stabilize the WCR against catastrophic instability growth. We then compute synthetic X-ray spectra and light curves and find that, compared to previous models, the X-ray spectra agree much better with XMM-Newton observations just prior to periastron. The narrow width of the 2009 X-ray minimum can also be reproduced. However, the models fail to reproduce the extended X-ray minimum from previous cycles. We conclude that the key to explaining the extended X-ray minimum is the rate of cooling of the companion star's postshock wind. If cooling is rapid then powerful NTSIs will heavily disrupt the WCR. Radiative inhibition of the companion star's preshock wind, albeit with a stronger radiation-wind coupling than explored in this work, could be an effective trigger.
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