Luminosities and mass-loss rates of SMC and LMC AGB stars and red supergiants

By M. Groenewegen, G. Sloan, Igor Soszynski, E. A. Petersen. 2009

137 citations recorded by the source corpus.

Context. Mass loss is one of the fundamental properties of Asymptotic Giant Branch (AGB) stars, and through the enrichment of the interstellar medium, AGB stars are key players in the life cycle of dust and gas in the universe. However, a quantitative understanding of the mass-loss process is still largely lacking, particularly its dependence on metallicity. Aims. To investigate the relation between mass loss, luminosity and pulsation period for a large sample of evolved stars in the Small and Large Magellanic Cloud. Methods. Dust radiative transfer models are presented for 101 carbon stars and 86 oxygen-rich evolved stars in the Magellanic Clouds for which 5–35 μ m Spitzer IRS spectra are available. The spectra are complemented with available optical and infrared photometry to construct the spectral energy distribution. A minimisation procedure is used to fit luminosity, mass-loss rate and dust temperature at the inner radius. Different effective temperatures and dust content are also considered. Periods from the literature and from new OGLE-III data are compiled and derived. Results. We derive (dust) mass-loss rates and luminosities for the entire sample. Based on luminosities, periods and amplitudes and colours, the O-rich stars are classified as foreground objects, AGB stars and Red Super Giants. For the O-rich stars silicates based on laboratory optical constants are compared to “astronomical silicates”. Overall, the grain type by Volk & Kwok (1988, ApJ, 331, 435) fits the data best. However, the fit based on laboratory optical constants for the grains can be improved by abandoning the small-particle limit. The influence of grain size, core-mantle grains and porosity are explored. A computationally convenient method that seems to describe the observed properties in the 10 μ m window are a distribution of hollow spheres with a large vacuum fraction (typically 70%), and grain size of about 1 μ m. Relations between mass-loss rates and luminosity and pulsation period are presented and compared to the predictions of evolutionary models, those by Vassiliadis & Wood (1993, ApJ, 413, 641) and their adopted mass-loss recipe, and those based on a Reimers mass-loss law with a scaling of a factor of five. The Vassiliadis & Wood models describe the data better, although there are also some deficiencies, in particular to the maximum adopted mass-loss rate. The derived mass-loss rates are compared to predictions by dynamical wind models and appear consistent with them at a level of a factor 2–4. A better understanding requires the determination of the expansion velocity from future observations from ALMA.  The OGLE-III data reveal an O-rich star in the SMC with a period of 1749 days. Its absolute magnitude of $M_{\rm bol}= -8.0$ makes it a good candidate for a super-AGB star.

Subfields: Astronomy and Astrophysics

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Citations in the corpus

The mass-loss rates of red supergiants and the de Jager prescription (2010, methodology): “Thanks to the works of Groenewegen et al. (2009) and Bonanos et al. (2010), we find that the RSGs of the Small Magellanic Cloud have mass-loss rates consistent with the de Jager rate scaled by (Z/Z⊙) α, where Z is the metallicity and α is 0.7.”
Mass loss of stars on the asymptotic giant branch (2018, background): “…and the MCs shows that dust-mass-loss rates decrease with metallicity for O-rich stars, but carbon stars with similar pulsation properties produce similar quantities of dust regardless of their initial metallicity (Sloan et al. 2008; Groenewegen et al. 2009; Lagadec et al. 2012; Sloan et al. 2016).”
The SAGE-Spec Spitzer Legacy Program: The Life Cycle of Dust and Gas in the Large Magellanic Cloud (2010, methodology): “…luminosities (Mbol) were calculated via a trapezoidal integration of the SED over the range of available photometric points (typically U band to IRAC 8 µm or MIPS 24 µm) and compared with published values (e.g. Groenewegen et al. 2009; Srinivasan et al. 2009; Jones et al. 2012; Riebel et al. 2012).”
SURVEYING THE AGENTS OF GALAXY EVOLUTION IN THE TIDALLY STRIPPED, LOW METALLICITY SMALL MAGELLANIC CLOUD (SAGE-SMC). II. COOL EVOLVED STARS (2011, methodology): “Individually, AGB stars produce comparatively small amounts of circumstellar dust (.10−9 M⊙ yr −1; e.g., van Loon 2000; Groenewegen et al. 2009).”
THE ACS NEARBY GALAXY SURVEY TREASURY. IX. CONSTRAINING ASYMPTOTIC GIANT BRANCH EVOLUTION WITH OLD METAL-POOR GALAXIES (2010, result): “Unfortunately, the properties of these models are inconsistent with the most basic observations of over 10 000 C-type AGB stars in the Magellanic Clouds (see Nikolaev & Weinberg 2000; Cioni & Habing 2003) with a significant fraction being at 3100 > Teff/K > 2650 (Groenewegen et al. 2009).”
Pulsational Pair-instability Supernovae (2016, background): “…driven mass loss and envelope instabilities which may play an important role in luminous blue variables (e.g. Bestenlehner et al. 2014; Owocki 2015; Petrov et al. 2016); and mass loss where grain formation is important, as in red supergiants (RSGs; Voors et al. 2000; Groenewegen et al. 2009).”
Super and massive AGB stars - IV. Final fates - Initial to final mass relation (2014, background): “…the mass-loss rate was thought to be lower at low metallicity (e.g. Bowen & Willson 1991; Willson 2000; Zijlstra 2004), recent theoretical (e.g. Mattsson et al. 2008) and observational (e.g. Groenewegen et al. 2009; Lagadec & Zijlstra 2008) studies suggest this may not always be the case.”