ALMA view of the circumstellar environment of the post-common-envelope-evolution binary system HD101584

TL;DR

This study uses ALMA observations to analyze the complex circumstellar environment of the post-AGB binary HD101584, revealing a bipolar structure likely shaped by energetic events beyond standard common-envelope evolution models.

Contribution

First detailed ALMA imaging of HD101584's circumstellar environment, challenging existing models of common-envelope ejection mechanisms.

Findings

Bipolar hour-glass morphology observed almost pole-on.

Kinetic energy of outflows exceeds orbital energy, inconsistent with standard models.

Evidence suggests additional processes influence circumstellar ejection.

Abstract

We study the circumstellar evolution of the binary HD101584, consisting of a post-AGB star and a low-mass companion, which is most likely a post-common-envelope-evolution system. We used ALMA observations of the 12CO, 13CO, and C18O J=2-1 lines and the 1.3mm continuum to determine the morphology, kinematics, masses, and energetics of the circumstellar environment. The circumstellar medium has a bipolar hour-glass structure, seen almost pole-on, formed by an energetic jet, about 150 km/s. We conjecture that the circumstellar morphology is related to an event that took place about 500 year ago, possibly a capture event where the companion spiraled in towards the AGB star. However, the kinetic energy of the accelerated gas exceeds the released orbital energy, and, taking into account the expected energy transfer efficiency of the process, the observed phenomenon does not match current common-envelope scenarios. This suggests that another process must augment, or even dominate, the ejection process. A significant amount of material resides in an unresolved region, presumably in the equatorial plane of the binary system.