Distance estimates for AGB stars from parallax measurements

Abstract

Context. Estimating the distances to asymptotic giant branch (AGB) stars using optical measurements of their parallaxes is not straightforward because of the large uncertainties introduced by their dusty envelopes, their large angular sizes, and their surface brightness variability. Aims. This paper aims to assess the reliability of the distances derived with Gaia DR3 parallaxes for AGB stars, and provide a new distance catalogue for a sample of ∼ 200 nearby AGB stars Methods. We compared the parallaxes from Gaia DR3 with parallaxes measured with maser observations with very long baseline interferometry (VLBI) to determine a statistical correction factor for the DR3 parallaxes using a sub-sample of 33 maser-emitting oxygen-rich nearby AGB stars. We then calculated the distances of a total of ∼ 200 AGB stars in the DEATHSTAR project using a Bayesian statistical approach on the corrected DR3 parallaxes and a prior based on the previously determined Galactic distribution of AGB stars. We performed radiative transfer modelling of the stellar and dust emission to determine the luminosity of the sources in the VLBI sub-sample based on the distances derived from maser parallaxes, and derived a new bolometric period-luminosity relation for Galactic oxygen-rich Mira variables. Results. We find that the errors on the Gaia DR3 parallaxes given in the Gaia DR3 catalogue are underestimated by a factor of 5.44 for the brightest sources (G < 8 mag). Fainter sources (8 ≤ G < 12) require a lower parallax error inflation factor of 2.74. We obtain a Gaia DR3 parallax zero-point offset of −0.077 mas for bright AGB stars. The offset becomes more negative for fainter AGB stars. After correcting the DR3 parallaxes, we find that the derived distances are associated with significant, asymmetrical errors for more than 40 % of the sources in our sample. We obtain a PL relation of the form M bol = (−3.31 ± 0.24) [log P − 2.5] + (−4.317 ± 0.060) for the oxygen-rich Mira variables in the Milky Way. A new distance catalogue based on these results is provided for the sources in the DEATHSTAR sample. Conclusions. The corrected Gaia DR3 parallaxes can be used to estimate distances for AGB stars using the AGB prior, but we confirm that one needs to be careful when the uncertainties on parallax measurements are larger than 20 %, which can result in model-dependent distances and source-dependent offsets. We find that a RUWE (re-normalised unit weight error) below 1.4 does not guarantee reliable distance estimates and we advise against the use of only the RUWE to measure the quality of Gaia DR3 astrometric data for individual AGB stars.

Properties of self-excited pulsations in 3D simulations of AGB stars and red supergiants

“…9, the 3D models are in relatively good agreement with both P-L relations, and within the parameter spread and scatter of the observed carbon and oxygen-rich Miras used to derive the respective P-L relations. There is evidence of the universality (that is one can use results from LMC sources in a different galactic environment) of a P-L relation for Miras (see Alvarez et al 1997;Whitelock et al 2008;Andriantsaralaza et al 2022). Nevertheless, one should be cautious in considering such universality, with counter arguments against it (e.g.…”

“…The first P-L relation was derived from observed carbon-rich Mira variables in the Large Magellanic Cloud (LMC), where a bolometric correction was applied in the K-band to derive the absolute bolometric luminosity (Whitelock et al 2009). Andriantsaralaza et al (2022) used improved constraints on the distances to oxygen-rich Mira variables in the Milky Way by making use of observations from Very Long Baseline Interferometry and masers of the AGB stars. They applied the radiative code DUSTY (Ivezic et al 1999) to derive the bolometric luminosity of the sources.…”

The intense production of silicates during the final AGB phases of intermediate mass stars

“…In all the other cases, a Bayesian approach can be used to infer distances (e.g. Bailer-Jones et al 2021;Andriantsaralaza et al 2022 for an application to AGB stars). In our case, the signal-to-noise of the only Gaia DR3 parallax available is so low that we decided not to implement this, so as to not bias our results as to the choice of the adopted prior.…”

Faint but Not Forgotten. I. First Results from a Search for Astrospheres around AGB Stars in the Far-ultraviolet

“…15-16); and the total ejected mass (col. 19), together with additional parameters relevant for the derivation of these parameters. We have adopted distances to our targets from Andriantsaralaza et al (2022) and when those are not available, from Bailer-Jones et al (2021; col. 2, Table 3). The mass-loss rates in Table 2 have been scaled to (i) the adopted distances and to (ii) a common value of the CO-to-H 2 abundance ratio-3 × 10 −4 for O-rich stars, and 10 −3 for C-rich stars (col. 12, Table 3).…”