Discovery of a planetary nebula surrounding the symbiotic star DT Serpentis

TL;DR

This paper reports the discovery of a planetary nebula around the symbiotic star DT Ser, highlighting its unique features and potential connection to post-AGB objects, suggesting the need for further detailed studies.

Contribution

It is the first confirmed case of a planetary nebula surrounding a symbiotic star, with detailed analysis of its morphology and possible evolutionary links.

Findings

Planetary nebula centered on DT Ser discovered

Nebula shows distortion and association with a nearby star

Infrared data indicates presence of cold dust shell

Abstract

We report the discovery of a planetary nebula centered on the poorly studied symbiotic binary star DT Ser. In a few other symbiotic stars spatially resolved nebulae have been discovered: however, only one of them might be a genuine planetary nebula, while the others are likely to originate in complex mass ejections episodes from the interacting binary central stars, possibly related to nova-like outbursts. The rim of the planetary nebula around DT Ser is severely distorted toward a brighter star, 5 arcsec away. In infrared WISE data, this star shows the presence of a detached cold dust shell such as those observed in post-AGB stars. The apparent association of the symbiotic star and its planetary nebula with the nearby possible post-AGB object is discussed. We also discuss the sparse and conflicting literature data that could support an observed variability of the surface brightness of the planetary nebula. The puzzling and intriguing characteristics displayed by DT Ser are surely worth further and more detailed investigations.