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

摘要

To measure the mass loss from dusty oxygen-rich (O-rich) evolved stars in theLarge Magellanic Cloud (LMC), we have constructed a grid of models ofspherically-symmetric dust shells around stars with constant mass-loss ratesusing 2Dust. These models will constitute the O-rich model part of the "Grid ofRed supergiant and Asymptotic giant branch star ModelS" (GRAMS). This modelgrid explores 4 parameters - stellar effective temperature from 2100 K - 4700K; luminosity from 10^3-10^6 L_Sun; dust shell inner radii of 3, 7, 11, and 15R_Star; and 10.0 micron 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 tocover the luminosity range required by the data. These models are offered tothe public on a website. The matching in color-magnitude diagrams andcolor-color diagrams to observed O-rich asymptotic giant branch (AGB) and redsupergiant (RSG) candidate stars from the SAGE and SAGE-Spec LMC samples and asmall sample of OH/IR stars is generally very good. The extreme AGB starcandidates from SAGE are more consistent with carbon-rich (C-rich) than O-richdust composition. Our model grid suggests lower limits to the mid-infraredcolors of the dustiest AGB stars for which the chemistry could be O-rich.Finally, the fitting of GRAMS models to SEDs of sources fit by other studiesprovides additional verification of our grid and anticipates future, moreexpansive efforts.