Abstract
In the centers of some planetary nebulae are found close binary stars. The formation of those planetary nebulae was likely through a common envelope event, which transformed an initially-wide progenitor binary into the currently observed close binary, while stripping the outer layers away. A common envelope event proceeds through several qualitatively different stages, each of which ejects matter at its own characteristic speed, and with a different degree of symmetry. Here, we present how typical post-common envelope ejecta looks kinematically a few years after the start of a common envelope event. We also show some asymmetric features we have detected in our simulations (jet-like structures, lobes, and hemispheres).
Highlights
About 20 percent of planetary nebulae (PN) were likely formed as a result of a common envelope (CE) event that took place in the progenitor binary [1]
One of the possible outcomes of a CE event is the formation of a binary that is more compact than the initial binary, where one of the stars is the hot core of the initial donor star
We find that deviations from a spherically symmetric shape are produced in the earlier stages of a CE event, either during the initial stage when most of the angular momentum is lost, or during the plunge
Summary
About 20 percent of planetary nebulae (PN) were likely formed as a result of a common envelope (CE) event that took place in the progenitor binary [1]. Proper simulation of PN formation due to a CE event must include a self-consistent three-dimensional simulation of the CE event with complete ejection, and the follow-up evolution during which the ejecta becomes a PN The latter is expected to include a long-term interaction with a pre-CE interstellar medium (presumably shaped by the previous episodes of mass loss by stellar winds), radiative cooling of the expanding envelope, stages of a fast wind, and re-ionization by a hot Galaxies 2018, 6, 75; doi:10.3390/galaxies6030075 www.mdpi.com/journal/galaxies. The envelope ejection is driven primarily by the recombination energy and is termed as a recombination outflow This fraction of the ejecta has almost uniform velocity; the rate of the mass loss in the analyzed simulations is 0.2–2 M year−1 , but can be expected to vary in general. This can only be modeled using one-dimensional codes, and the kinematic profile of the ejecta during a self-regulated spiral-in is not entirely clear
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