Detection of Keplerian dynamics in a disk around the post-AGB star AC Her

TL;DR

This study presents interferometric observations confirming the presence of a Keplerian disk around the post-AGB star AC Her, expanding understanding of disk structures in evolved stars and their role in stellar evolution.

Contribution

First direct detection and characterization of a Keplerian disk around a post-AGB star similar to the Red Rectangle, using high-resolution CO emission data.

Findings

Confirmed Keplerian dynamics in the disk around AC Her

Derived disk properties such as size, temperature, and central mass

Supported the hypothesis that many evolved stars are surrounded by Keplerian disks

Abstract

So far, only one rotating disk has been clearly identified and studied in AGB or post-AGB objects (in the Red Rectangle), by means of observations with high spectral and spatial resolution. However, disks are thought to play a key role in the late stellar evolution and are suspected to surround many evolved stars. We aim to extend our knowledge on these structures. We present interferometric observations of CO J=2-1 emission from the nebula surrounding the post-AGB star AC Her, a source belonging to a class of objects that share properties with the Red Rectangle and show hints of Keplerian disks. We clearly detect the Keplerian dynamics of a second disk orbiting an evolved star. Its main properties (size, temperature, central mass) are derived from direct interpretation of the data and model fitting. With this we confirm that there are disks orbiting the stars of this relatively wide class of post-AGB objects