• DOI:10.1093/mnras/stt1871
• Corpus ID: 118407295

Constraints on decreases in η Carinae's mass-loss from 3D hydrodynamic simulations of its binary colliding winds

@article{Madura2013ConstraintsOD,
  title={Constraints on decreases in $\eta$ Carinae's mass-loss from 3D hydrodynamic simulations of its binary colliding winds},
  author={Thomas I. Madura and Theodore R. Gull and Atsuo T. Okazaki and Christopher Michael Post Russell and Stanley P. Owocki and Jose H Groh and Michael F. Corcoran and Kenji Hamaguchi and Mairan Macedo Teodoro},
  journal={Monthly Notices of the Royal Astronomical Society},
  year={2013},
  volume={436},
  pages={3820-3855}
}

• T. Madura, T. Gull, +6 authors M. Teodoro
• Published 1 October 2013
• Physics
• Monthly Notices of the Royal Astronomical Society

Recent work suggests that the mass-loss rate of the primary star Eta-A in the massive colliding wind binary Eta Carinae dropped by a factor of 2-3 between 1999 and 2010. We present result from large- (+/- 1545 au) and small- (+/- 155 au) domain, 3D smoothed particle hydrodynamics (SPH) simulations of Eta Car's colliding winds for three Eta-A mass-loss rates ( (dot-M(sub Eta-A) = 2.4, 4.8 and 8.5 10(exp 4) M(solar)/ yr), investigating the effects on the dynamics of the binary wind-wind collision (WWC). These simulations include orbital motion, optically thin radiative cooling and radiative forces. We find that dot-M Eta-A greatly affects the time-dependent hydrodynamics at all spatial scales investigated. The simulations also show that the post-shock wind of the companion star Eta-B switches from the adiabatic to the radiative-cooling regime during periastron passage (Phi approx.= 0.985-1.02). This switchover starts later and ends earlier the lower the value of dot-M Eta-A and is caused by the encroachment of the wind of Eta-A into the acceleration zone of Eta-B's wind, plus radiative inhibition of Eta-B's wind by Eta-A. The SPH simulations together with 1D radiative transfer models of Eta-A's spectra reveal that a factor of 2 or more drop in dot-M EtaA should lead to substantial changes in numerous multiwavelength observables. Recent observations are not fully consistent with the model predictions, indicating that any drop in dot- M Eta-A was likely by a factor of approx. < 2 and occurred after 2004. We speculate that most of the recent observed changes in Eta Car are due to a small increase in the WWC opening angle that produces significant effects because our line of sight to the system lies close to the dense walls of the WWC zone. A modest decrease in dot-M Eta-A may be responsible, but changes in the wind/stellar parameter of Eta-B, while less likely, cannot yet be fully ruled out. We suggest observations during Eta-Car's next periastron in 2014 to further test for decreases in dot-M Eta-A. If dot-M Eta-A is declining and continues to do so, the 2014 X-ray minimum should be even shorter than that of 2009.