An occultation event in a triple post-AGB star

TL;DR

This study reports a long-lasting occultation event in a post-AGB star, modeled as caused by a circumbinary disk, revealing complex binary interactions and dust dynamics in a planetary nebula system.

Contribution

It provides the first detailed observation and modeling of an occultation event in a post-AGB star with a circumbinary disk, highlighting binary interactions.

Findings

Occultation lasted nearly 3 years with a secondary minimum 9 years later.

The event is modeled as caused by a circumbinary disk with an 18-year period.

Evidence suggests an additional companion with a 23-day orbital period.

Abstract

We study the post-AGB central star of the (bipolar) Galactic bulge planetary nebula M 2-29. We have obtained additional HST imaging and SAAO spectroscopy of the object. The star showed a pronounced, long-lasting occultation with subsequent recovery. The event lasted for almost 3 years, with a secondary minimum 9 years later. The photometric behaviour of M 2-29 resembles the dust-occultation events seen in NGC 2346, and is modeled as an occultation by a circumbinary disk, where the binary period is 18 yr. Modulation during the decline shows evidence for another companion with a period of 23 days.