The mass-loss return from evolved stars to the Large Magellanic Cloud

Abstract

Context. Outflows from asymptotic giant branch (AGB) and red supergiant (RSG) stars inject dust into the interstellar medium. The total rate of dust return provides an important constraint to galactic chemical evolution models. However, this requires detailed radiative transfer (RT) modeling of individual stars, which becomes impractical for large data sets. An alternative approach is to select the best-fit spectral energy distribution (SED) from a grid of dust shell models, allowing for a faster determination of the luminosities and mass-loss rates for entire samples. Aims. We have developed the Grid of RSG and AGB ModelS (GRAMS) to measure the mass-loss return from evolved stars. The models span the range of stellar, dust shell and grain properties relevant to evolved stars. The GRAMS model database will be made available to the scientific community. In this paper we present the carbon-rich AGB model grid and compare our results with photometry and spectra of Large Magellanic Cloud (LMC) carbon stars from the SAGE (Surveying the Agents of Galaxy Evolution) and SAGE-Spec programs. Methods. We generate models for spherically symmetric dust shells using the 2Dust code, with hydrostatic models for the central stars. The model photospheres have effective temperatures between 2600 and 4000 K and luminosities from ∼2000 L to ∼40 000 L . Assuming a constant expansion velocity, we explore five values of the inner radius R in of the dust shell (1.5, 3, 4.5, 7 and 12 R star ). We fix the outer radius at 1000 R in . Based on the results from our previous study, we use amorphous carbon dust mixed with 10% silicon carbide by mass. The grain size distribution follows a power-law and an exponential falloff at large sizes. The models span twenty-six values of 11.3 μm optical depth, ranging from 0.001 to 4. For each model, 2Dust calculates the output SED from 0.2 to 200 μm. Results. Over 12 000 models have dust temperatures below 1800 K. For these, we derive synthetic photometry in optical, nearinfrared and mid-infrared filters for comparison with available data. We find good agreement with magnitudes and colors observed for LMC carbon-rich and extreme AGB star candidates from the SAGE survey, as well as spectroscopically confirmed carbon stars from the SAGE-Spec study. Our models reproduce the IRAC colors of most of the extreme AGB star candidates, consistent with the expectation that a majority of these enshrouded stars have carbon-rich dust. Finally, we fit the SEDs of some well-studied carbon stars and compare the resulting luminosities and mass-loss rates with those from previous studies.

LMC S63: a historical reappraisal of the outburst behaviour of a deeply eclipsing Magellanic symbiotic star

“…Unfortunately, they misclassified LMC S63 as O-rich star, which could affect their fitting result. We repeated their procedure by fitting the GRAMS C-rich grid of models of dust shells around red supergiant and AGB stars (Srinivasan, Sargent & Meixner 2011) to the same mid-infared photometry as Riebel et al (2012), supplemented with data from WISE (Cutri et al 2012) and DENIS (Cioni et al 2000) catalogs. Using VOSA (Bayo et al 2008) we performed a Bayesian analysis of the data.…”

Synthetic photometry for carbon-rich giants

“…Recently, efforts were made to interpret the SEDs of these objects (defined by photometry compiled from various catalogues; cf. Srinivasan et al 2009) with the help of a model grid Srinivasan et al 2011;Riebel et al 2012). This SED fitting led to the conclusion (cf.…”

Planetary nebulae in the Small Magellanic Cloud

“…For example, such comparisons have allowed primarily to estimate the extension of the third dredge-up (hereinafter TDU), i.e. the inwards penetration of the bottom of the convective envelope in the phase following each thermal pulse (Izzard et al 2004;Girardi & Marigo 2007;Groenewegen et al 2007;Riebel et al 2010Riebel et al , 2012Srinivasan et al 2009Srinivasan et al , 2011Boyer et al 2011Boyer et al , 2012. More recent studies were focused on the dust production by AGB stars in the MC and the characterisation of the most obscured sources (Dell'Agli et al 2014, 2015aVentura et al 2015.…”