The Gaia Catalogue of Galactic AGB Stars

I. OH/IR stars

¹ Universidad San Pablo CEU, E-28925 Alcorcón, Madrid, Spain
² Spanish Virtual Observatory (SVO), Spain
³ Centro de Astrobiología (CAB), CSIC-INTA, Camino Bajo del Castillo s/n, E-28692 Villanueva de la Cañada, Madrid, Spain
⁴ Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, D-21029 Hamburg, Germany
⁵ European Space Agency (ESA), European Space Astronomy Centre (ESAC), Camino Bajo del Castillo, s/n, Urbanización Villafranca del Castillo, E-28692 Villanueva de la Cañada, Madrid, Spain

^⋆ Corresponding author: belen.lopezmarti@ceu.es

Received: 22 November 2024
Accepted: 31 March 2025

Abstract

Context. The Gaia mission discovered several hundred thousand long-period variables and measured parallaxes for many of them. These stars will allow us to study populations of variable stars in the Milky Way, including asymptotic giant branch (AGB) stars.

Aims. This paper describes the identification of Gaia counterparts of a sample of oxygen-rich AGB stars with OH maser emission as a first step towards the compilation of a general Gaia Catalogue of Galactic AGB stars. With this catalogue, tests of evolutionary models for the AGB star population in the solar neighbourhood become feasible.

Methods. We cross-matched AGB star candidates showing OH maser emission with the Gaia DR3 release using a cross-match with AllWISE and 2MASS as intermediate steps to avoid ambiguities. With the help of the Virtual Observatory, we retrieved photometric data from the near-ultraviolet to the far-infrared and built spectral energy distributions (SEDs) of the sources. The SEDs were fitted with theoretical models. The fit results, together with information from the literature, allowed us to clean the sample from non-AGB stars. For the AGB stars, bolometric fluxes were obtained. Distances based on Gaia parallaxes were used to derive the stellar luminosities.

Results. We identified unique Gaia counterparts for 1487 OH masers. Of these, 1172 had an unambiguous classification as AGB stars. These sources make up the Gaia OH/IR star sample. Parallaxes with relative errors < 20% and astrometric excess noise < 1.5 mas were available for 222 OH/IR stars.

Conclusions. The study of the AGB population in the solar neighbourhood is limited by the obscuration by circumstellar dust, as Gaia DR3 only provides parallaxes for a few of our candidates. The location of the OH/IR stars matches that of LPV discovered by Gaia in the (BP–RP; G_abs) diagram, but the OH/IR star sample is biased towards redder colours (BP–RP > 4) mag and larger amplitudes (> 1 mag in the G-band), which are typical for periodic large-amplitude Mira variables.