We present results from the first application of the Grid of Red Supergiant and Asymptotic Giant Branch M odelS (GRAMS) model grid to the entire evolved stellar population of the Large Magellanic Cloud (LMC). GRAMS is a pre-computed grid of 80 843 radiative transfer (RT) models of evolved stars and circumstellar dust shells composed of either silicate or carbonaceous dust. We fit GRAMS models to ∼30 000 Asymptotic Giant Branch (AGB) and Red Supergiant (RSG) stars in the LMC, using 12 bands of photometry from the optical to the mid-infrared. Our published dataset consists of thousands of evolved stars with individually determined evolutionary parameters such as luminosity and mass-loss rate. The GRAMS grid has a greater than 80% accuracy rate discriminating between Oxygen-and Carbon-rich chemistry. The global dust injection rate to the interstellar medium (ISM) of the LMC from RSGs and AGB stars is on the order of 1.5 × 10 −5 M yr −1 , equivalent to a total mass injection rate (including the gas) into the ISM of ∼ 5 × 10 −3 M yr −1 . Carbon stars inject two and a half times as much dust into the ISM as do O-rich AGB stars, but the same amount of mass. We determine a bolometric correction factor for C-rich AGB stars in the K s band as a function of J -K s color, BC Ks = −0.40(J − K s ) 2 + 1.83(J − K s ) + 1.29. We determine several IR color proxies for the dust mass-loss rate (Ṁ d ) from C-rich AGB stars, such as logṀ d = −18.90 (Ks−[8.0])+3.37 − 5.93. We find that a larger fraction of AGB stars exhibiting the 'long-secondary period' phenomenon are O-rich than stars dominated by radial pulsations, and AGB stars without detectable mass-loss do not appear on either the first-overtone or fundamental-mode pulsation sequences.

No abstract

The lifecycle of dust in the interstellar medium (ISM) is heavily influenced by outflows from asymptotic giant branch (AGB) and red supergiant (RSG) stars, a large fraction of which is contributed by a few very dusty sources. We compute the dust input to the Small Magellanic Cloud (SMC) by fitting the multi-epoch mid-infrared spectral energy distributions (SEDs) of AGB/RSG candidates with models from the Grid of RSG and AGB ModelS (GRAMS) grid, allowing us to estimate the luminosities and dust-production rates (DPRs) of the entire population. By removing contaminants, we guarantee a high-quality dataset with reliable DPRs and a complete inventory of the dustiest sources. We find a global AGB/RSG dust-injection rate of (1.3 ± 0.1) × 10 −6 M ⊙ yr −1 , in agreement with estimates derived from mid-infrared colours and excess fluxes. As in the LMC, a majority (66%) of the dust arises from the extreme AGB stars, which comprise only ≈7% of our sample. A handful of far-infrared sources, whose 24 µm fluxes exceed their 8 µm fluxes, dominate the dust input. Their inclusion boosts the global DPR by ≈1.5×, making it necessary to determine whether they are AGB stars. Model assumptions, rather than missing data, are the major sources of uncertainty; depending on the choice of dust shell expansion speed and dust optical constants, the global DPR can be up to ≈10 times higher. Our results suggest a non-stellar origin for the SMC dust, barring as yet undiscovered evolved stars with very high DPRs.

SN 2010jl was an extremely bright, Type IIn SNe which showed a significant IR excess no later than 90 days after explosion. We have obtained Spitzer 3.6 and 4.5 µm and JHK observations of SN 2010jl ∼90 days post explosion. Little to no reddening in the host galaxy indicated that the circumstellar material lost from the progenitor must lie in a torus inclined out of the plane of the sky. The likely cause of the high mid-IR flux is the reprocessing of the initial flash of the SN by pre-existing circumstellar dust. Using a 3D Monte Carlo Radiative Transfer code, we have estimated that between 0.03-0.35 M ⊙ of dust exists in a circumstellar torus around the SN located 6 × 10 17 cm away from the SN and inclined between 60-80 • to the plane of the sky. On day 90, we are only seeing the illumination of approximately 5% of this torus, and expect to see an elevated IR flux from this material up until day ∼ 450. It is likely this dust was created in an LBV-like mass loss event of more than 3 M ⊙ , which is large but consistent with other LBV progenitors such as η Carinae.

We combine variability information from the MAssive Compact Halo Objects (MA-CHO) survey of the Large Magellanic Cloud (LMC) with infrared photometry from the Spitzer Space Telescope Surveying the Agents of a Galaxy's Evolution (SAGE) survey to create a dataset of ∼30 000 variable red sources. We photometrically classify these sources as being on the first ascent of the Red Giant Branch (RGB), or as being in one of three stages along the Asymptotic Giant Branch (AGB): oxygen-rich, carbonrich, or highly reddened with indeterminate chemistry ("extreme" AGB candidates). We present linear period-luminosity relationships for these sources using 8 separate infrared bands (J, H, K s , 3.6, 4.5, 5.8, 8.0, and 24 µm) as proxies for the luminosity. We find that the wavelength dependence of the slope of the period-luminosity relationship is arXiv:1007.5029v1 [astro-ph.SR] 28 Jul 2010 -2different for different photometrically determined classes of AGB stars. Stars photometrically classified as O-rich show the least variation of slope with wavelength, while dust enshrouded extreme AGB stars show a pronounced trend toward steeper slopes with increasing wavelength. We find that O-rich AGB stars pulsating in the fundamental mode obey a period-magnitude relation with a slope of −3.41 ± 0.04 when magnitude is measured in the 3.6 µm band, in contrast to C-rich AGB stars, which obey a relation of slope −3.77 ± 0.05.