3 Dimensional Simulations of the Common Envelope Evolution of Massive X-Ray Binaries

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Session 121 -- Early Stars, X-Ray Binaries, Theory
Oral presentation, Thursday, 12, 1995, 2:00pm - 3:30pm

[121.04] 3 Dimensional Simulations of the Common Envelope Evolution of Massive X-Ray Binaries

J. L. Terman, R. E. Taam (Northwestern U.), L. Hernquist (UCSC/UCO)

Results of three-dimensional simulations of the common envelope evolution of binary systems with properties similar to those of high mass X-ray binaries are discussed. It is found that the final outcome of the common envelope phase depends upon the structure of the evolved companion. In particular, it is found that the entire common envelope can be ejected by the interaction of the neutron star with a red supergiant companion in binaries with orbital periods in the range of $\gapprox 0.8 - 2$ yrs (for companions of mass 12 - 24 $\msun$) which are similar to those of long period Be X-ray binaries. For these systems, the structure of the progenitor star is characterized by a steep density gradient above the helium core, and the common envelope phase ends with a spin up of the envelope to within 50 - 60\% of co-rotation and with a slow mass outflow. The efficiency of mass ejection is found to be $\sim 30 - 40\%$. For less evolved companions, there is insufficient energy in the orbit to unbind the common envelope and only a fraction of it is ejected. Since the time scale for orbital decay is always shorter than the mass loss time scale from the common envelope, the two cores will likely merge to form a Thorne-Zytkow object. Implications for the origin of Cyg X-3, an X-ray source consisting of a Wolf Rayet star and a compact companion, and for the fate of the remnant binary consisting of a helium star and a neutron star are briefly discussed.

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