On the nature of the most obscured C-rich AGB stars in the Magellanic Clouds

Abstract

The stars in the Magellanic Clouds with the largest degree of obscuration are used to probe the highly uncertain physics of stars in the asymptotic giant branch (AGB) phase of evolution. Carbon stars in particular, provide key information on the amount of third dredge-up (TDU) and mass loss. We use two independent stellar evolution codes to test how a different treatment of the physics affects the evolution on the AGB. The output from the two codes are used to determine the rates of dust formation in the circumstellar envelope, where the method used to determine the dust is the same for each case. The stars with the largest degree of obscuration in the LMC and SMC are identified as the progeny of objects of initial mass $2.5-3M_{\odot }$ and $\sim 1.5M_{\odot }$, respectively. This difference in mass is motivated by the difference in the star formation histories of the two galaxies, and offers a simple explanation of the redder infrared colours of C-stars in the LMC compared to their counterparts in the SMC. The comparison with the Spitzer colours of C-rich AGB stars in the SMC shows that a minimum surface carbon mass fraction $X(C)\sim 5\times 10^{-3}$ must have been reached by stars of initial mass around $1.5M_{\odot }$. Our results confirm the necessity of adopting low-temperature opacities in stellar evolutionary models of AGB stars. These opacities allow the stars to obtain mass-loss rates high enough ($\gtrsim 10^{-4}{M}_{\odot }/yr$) to produce the amount of dust needed to reproduce the Spitzer colours

14 pages, 5 figures, 1 table; accepted for publication in MNRAS Main Journal

References in corpus (17)

• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• Evidence for TP-AGB stars in high redshift galaxies, and their effect on deriving stellar population parameters
• Evolution of interstellar dust and stardust in the solar neighbourhood
• Spitzer SAGE survey of the Large Magellanic Cloud II: Evolved Stars and Infrared Color Magnitude Diagrams
• AGB stars in the Magellanic Clouds. II. The rate of star formation across the LMC
• A Spitzer mid-infrared spectral survey of mass-losing carbon stars in the Large Magellanic Cloud
• The Magellanic zoo: Mid-infrared Spitzer spectroscopy of evolved stars and circumstellar dust in the Magellanic Clouds
• Molecules and dust production in the Magellanic Clouds
• The Mass-Loss Return From Evolved Stars to the LMC: Empirical Relations for Excess Emission at 8 and 24 μm
• Spitzer spectroscopy of carbon stars in the Small Magellanic Cloud
• Dust-driven Winds and Mass Loss of C-rich AGB Stars with subsolar Metallicities
• AGB stars in the LMC: evolution of dust in circumstellar envelopes
• AGB stars in the SMC: evolution and dust properties based on Spitzer observations
• The Large Magellanic Cloud as a laboratory for Hot Bottom Burning in massive Asymptotic Giant Branch stars
• Identification of a Class of Low-Mass Asymptotic Giant Branch Stars Struggling to Become Carbon Stars in the Magellanic Clouds
• Dissecting the Spitzer color-magnitude diagrams of extreme LMC AGB stars
• Physical properties of the jet in 0836+710 revealed by its transversal structure

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• The infrared spectral properties of Magellanic carbon stars
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• Estimating the dust production rate of carbon stars in the Small Magellanic Cloud
• Studying the evolution of AGB stars in the Gaia epoch
• Evolved stars in the Local Group galaxies - II. AGB, RSG stars and dust production in IC10
• The evolution of Galactic planetary nebula progenitors through the comparison of their nebular abundances with AGB yields
• Evolved stars in the Local Group galaxies. I. AGB evolution and dust production in IC 1613
• Understanding the evolution and dust formation of carbon stars in the LMC with a look at the JWST
• The ALMA detection of CO rotational line emission in AGB stars in the Large Magellanic Cloud
• Empirical Constraints on the Nucleosynthesis of Nitrogen
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• Evolved stars in the Local Group galaxies - III. AGB and RSG stars in Sextans A
• A WISE view on extreme AGB stars
• A dearth of OH/IR stars in the Small Magellanic Cloud
• Optical properties of amorphous carbon dust around C-stars: new constraints from 2MASS and Gaia observations
• Infrared Properties of Asymptotic Giant Branch Stars in Our Galaxy and the Magellanic Clouds
• Nucleosynthetic yields of intermediate-mass primordial to extremely metal-poor stars
• Carbon Abundances in Compact Galactic Planetary Nebulae: An Ultraviolet spectroscopic study with the Space Telescope Imaging Spectrograph (STIS)
• Dust Production around Carbon-Rich Stars: The Role of Metallicity
• A homogeneous view of asymptotic giant branch carbon stars as seen by Gaia
• Gas and dust from extremely metal-poor AGB stars