The mass-loss return from evolved stars to the Large Magellanic Cloud. IV. Construction and validation of a grid of models for oxygen-rich AGB stars, red supergiants, and extreme AGB stars.
SARGENT B.A., SRINIVASAN S. and MEIXNER M.
Abstract (from CDS):
To measure the mass loss from dusty oxygen-rich (O-rich) evolved stars in the Large Magellanic Cloud (LMC), we have constructed a grid of models of spherically symmetric dust shells around stars with constant mass-loss rates using 2Dust. These models will constitute the O-rich model part of the "Grid of Red supergiant and Asymptotic giant branch star ModelS" (GRAMS). This model grid explores four parameters–stellar effective temperature from 2100 K to 4700 K; luminosity from 103 to 106 L☉; dust shell inner radii of 3, 7, 11, and 15 Rstar; and 10.0 µm optical depth from 10–4 to 26. From an initial grid of ∼1200 2Dust models, we create a larger grid of ∼69,000 models by scaling to cover the luminosity range required by the data. These models are available online to the public. The matching in color-magnitude diagrams and color-color diagrams to observed O-rich asymptotic giant branch (AGB) and red supergiant (RSG) candidate stars from the SAGE and SAGE-Spec LMC samples and a small sample of OH/IR stars is generally very good. The extreme AGB star candidates from SAGE are more consistent with carbon-rich (C-rich) than O-rich dust composition. Our model grid suggests lower limits to the mid-infrared colors of the dustiest AGB stars for which the chemistry could be O-rich. Finally, the fitting of GRAMS models to spectral energy distributions of sources fit by other studies provides additional verification of our grid and anticipates future, more expansive efforts.
circumstellar matter - galaxies: individual: Large Magellanic Cloud - infrared: stars - radiative transfer - stars: AGB and post-AGB - stars: mass-loss