Analysis of the Gaia DR3 planetary nebula candidates and the possible symbiotic stars among them

TL;DR

This study analyzes Gaia DR3 emission-line objects, identifying true planetary nebulae and symbiotic stars using spectral data and follow-up observations, revealing several new symbiotic systems and other stellar objects.

Contribution

It provides a detailed classification of Gaia DR3 PN candidates, distinguishing true PNe from mimics like symbiotic stars through spectral analysis and follow-up observations.

Findings

Identified nine D- or D'-type symbiotic systems among the candidates.

Discovered one planetary nebula in the LMC.

Found one polar cataclysmic variable and three possible Be stars.

Abstract

The Gaia DR3, released in June 2022, included low-resolution BP/RP (XP) spectra that have been exploited for the classification of various types of emission-line objects using machine-learning techniques. The Gaia Extended Stellar Parametrizer for Emission-Line Stars (ESP-ELS) algorithm identified 273 sources as potential planetary nebulae (PNe). We aim to analyze the PN sample produced by the ESP-ELS algorithm to investigate the true nature of the objects classified as PNe. We extracted all sources from the catalog classified as PNe by the ESP-ELS algorithm and filtered out 200 objects with secure classifications available in the literature. Of these, $\sim$65% correspond to known Galactic or Magellanic compact PNe, and $\sim$20% to D- or D'-type symbiotic systems. The XP spectra of the remaining sources were visually inspected, leading to a subset of 14 promising candidates showing strong emission features attributable to H$\alpha$ and [O III] $\lambda$5007. Although typical of PNe, such features are also consistent with D- or D'-type symbiotics, known to mimic compact PNe. We obtained spectroscopic follow-up observations for these objects with the 2SPOT facilities in Chile and France, complemented by an analysis of archival photometric data to further constrain their nature. We report the identification of nine bona-fide or likely D- or D'-type symbiotic systems, one planetary nebula in the LMC, one polar cataclysmic variable, and three possible Be stars in (or in the direction of) the SMC, within our sample of 14 objects.