A homogeneous view of asymptotic giant branch carbon stars as seen by Gaia

TL;DR

This study provides a comprehensive analysis of asymptotic giant branch carbon stars using Gaia, 2MASS, and WISE data, deriving stellar parameters and exploring environmental effects on their properties.

Contribution

It introduces a homogeneous spectral energy distribution analysis of a large sample of carbon stars, linking variability, mass-loss, and environmental factors.

Findings

Mass-loss rates range from 1e-11 to 1e-4 Msun/yr.

Effective temperatures peak around 3150 K.

Variability amplitude correlates with mass-loss rate.

Abstract

Carbon stars on the asymptotic giant branch are major contributors to galactic dust enrichment, with gas mass-loss rates up to 1e-4 Msun/yr. We present a homogeneous spectral energy distribution analysis of the Gaia DR3 Golden Sample of carbon stars in the Milky Way and Magellanic Clouds. Our dataset includes 14,747 sources with multi-band photometry from Gaia, 2MASS, and WISE, combined with recent distance and extinction estimates. For a subsample of 2,494 Mira variables, we model multi-band light curves to derive accurate mean magnitudes. Stellar and circumstellar parameters are obtained by fitting observations with a large grid of synthetic spectra computed with the DUSTY radiative transfer code using COMARCS atmospheres. We derive effective temperature, optical depth, and gas mass-loss rate for each source. The distributions peak around Teff = 3150 K, with mass-loss rates spanning 1e-11 to 1e-4 Msun/yr and inner dust temperatures near 1000 K. We find a correlation between variability amplitude and mass-loss rate. This framework provides a statistically robust view of carbon stars across environments with different metallicities. Apparent environmental dependencies are influenced by luminosity distributions and selection effects rather than purely intrinsic metallicity differences. The combined Gaia and WISE selection limits the detection of both highly obscured and faint Magellanic Cloud sources, but the observed trends remain significant within the sampled populations.