Search

We report the detection of broad, flat-topped emission in the fine-structure lines of [Ne V], [Ne VI], and [O IV] in mid-infrared spectra of the O9 V star 10 Lacertae obtained with JWST/MIRI. Optically thin emission in these high ions traces a hot, low-density component of the wind. The observed line fluxes imply a mass-loss rate of 2-4 x 10^8 Msun/yr, which is an order of magnitude larger than previous estimates based on UV and optical diagnostics. The presence of this hot component reconciles measured values of the mass-loss rate with theoretical predictions, and appears to solve the "weak wind" problem for the particular case of 10 Lac., Comment: 8 pages, 5, figures, submitted to ApJL

The absolute flux calibration of the Mid-Infrared Instrument Imaging and Coronagraphy is based on observations of multiple stars taken during the first 2.5 years of JWST operations. The observations were designed to ensure that the flux calibration is valid for a range of flux densities, different subarrays, and different types of stars. The flux calibration was measured by combining observed aperture photometry corrected to infinite aperture with predictions based on previous observations and models of stellar atmospheres. A subset of these observations were combined with model point-spread-functions to measure the corrections to infinite aperture. Variations in the calibration factor with time, flux density, background level, type of star, subarray, integration time, rate, and well depth were investigated, and the only significant variations were with time and subarray. Observations of the same star taken approximately every month revealed a modest time-dependent response loss seen mainly at the longest wavelengths. This loss is well characterized by a decaying exponential with a time constant of ~200 days. After correcting for the response loss, the band-dependent scatter around the corrected average (aka repeatability) was found to range from 0.1 to 1.2%. Signals in observations taken with different subarrays can be lower by up to 3.4% compared to FULL frame. After correcting for the time and subarray dependencies, the scatter in the calibration factors measured for individual stars ranges from 1 to 4% depending on the band. The formal uncertainties on the flux calibration averaged for all observations are 0.3 to 1.0%, with longer-wavelength bands generally having larger uncertainties., Comment: 26 pages, 17 figures, submitted to AJ

Context. The modeling of stellar spectra of flux standards observed by the Hubble and James Webb space telescopes requires a large synthetic spectral library that covers a wide atmospheric parameter range. Aims. The aim of this paper is to present and describe the calculation methods behind the updated version of the BOSZ synthetic spectral database, which was originally designed to fit the CALSPEC flux standards. These new local thermodynamic equilibrium (LTE) models incorporate both MARCS and ATLAS9 model atmospheres, updated continuous opacities, and 23 new molecular line lists. Methods. The new grid was calculated with Synspec using the LTE approximation and covers metallicities [M/H] from -2.5 to 0.75 dex, [alpha/M] from -0.25 to 0.5 dex, and [C/M] from -0.75 to 0.5 dex, providing spectra for 336 unique compositions. Calculations for stars between 2800 and 8000 K use MARCS model atmospheres, and ATLAS9 is used between 7500 and 16,000 K. Results. The new BOSZ grid includes 628,620 synthetic spectra from 50 nm to 32 microns with models for 495 Teff - log g parameter pairs per composition and per microturbulent velocity. Each spectrum has eight different resolutions spanning a range from R = 500 to 50,000 as well as the original resolution of the synthesis. The microturbulent velocities are 0, 1, 2, and 4 km/s. Conclusions. The new BOSZ grid extends the temperature range to cooler temperatures compared to the original grid because the updated molecular line lists make modeling possible for cooler stars. A publicly available and consistently calculated database of model spectra is important for many astrophysical analyses, for example spectroscopic surveys and the determination of stellar elemental compositions., Comment: 11 pages, 7 figures, 5 tables, published in A&A, new version includes proof corrections

Water is a key ingredient for the emergence of life as we know it. Yet, its destruction and reformation in space remains unprobed in warm gas. Here, we detect the hydroxyl radical (OH) emission from a planet-forming disk exposed to external far-ultraviolet (FUV) radiation with the James Webb Space Telescope. The observations are confronted with the results of quantum dynamical calculations. The highly excited OH infrared rotational lines are the tell-tale signs of H2O destruction by FUV. The OH infrared ro-vibrational lines are attributed to chemical excitation via the key reaction O+H=OH+H which seeds the formation of water in the gas-phase. We infer that the equivalent of the Earth ocean's worth of water is destroyed per month and replenished. These results show that under warm and irradiated conditions water is destroyed and efficiently reformed via gas-phase reactions. This process, assisted by diffusive transport, could reduce the HDO/H2O ratio in the warm regions of planet-forming disks., Comment: Version submitted to Nature Astronomy

(Abridged) Mid-infrared observations of photodissociation regions (PDRs) are dominated by strong emission features called aromatic infrared bands (AIBs). The most prominent AIBs are found at 3.3, 6.2, 7.7, 8.6, and 11.2 $\mu$m. The most sensitive, highest-resolution infrared spectral imaging data ever taken of the prototypical PDR, the Orion Bar, have been captured by JWST. We provide an inventory of the AIBs found in the Orion Bar, along with mid-IR template spectra from five distinct regions in the Bar: the molecular PDR, the atomic PDR, and the HII region. We use JWST NIRSpec IFU and MIRI MRS observations of the Orion Bar from the JWST Early Release Science Program, PDRs4All (ID: 1288). We extract five template spectra to represent the morphology and environment of the Orion Bar PDR. The superb sensitivity and the spectral and spatial resolution of these JWST observations reveal many details of the AIB emission and enable an improved characterization of their detailed profile shapes and sub-components. While the spectra are dominated by the well-known AIBs at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 $\mu$m, a wealth of weaker features and sub-components are present. We report trends in the widths and relative strengths of AIBs across the five template spectra. These trends yield valuable insight into the photochemical evolution of PAHs, such as the evolution responsible for the shift of 11.2 $\mu$m AIB emission from class B$_{11.2}$ in the molecular PDR to class A$_{11.2}$ in the PDR surface layers. This photochemical evolution is driven by the increased importance of FUV processing in the PDR surface layers, resulting in a "weeding out" of the weakest links of the PAH family in these layers. For now, these JWST observations are consistent with a model in which the underlying PAH family is composed of a few species: the so-called 'grandPAHs'., Comment: 25 pages, 10 figures, to appear in A&A

We use data from the Transiting Exoplanet Survey Satellite (TESS) to search for, and set limits on, optical to near-infrared photometric variability of the well-vetted, candidate James Webb Space Telescope (JWST) spectrophotometric standards. Our search of 37 of these candidate standards has revealed measurable periodic variability in 15 stars. The majority of those show variability that is less than half a percent; however, four stars are observed to vary photometrically, from minimum to maximum flux, by more than 1% (the G dwarf HD 38949 and three fainter A dwarfs). Variability of this size would likely impact the error budget in the spectrophotometric calibration of the science instruments aboard JWST. For the 22 candidate standards with no detected variability, we report upper limits on the observed changes in flux. Despite some systematic noise, all stars brighter than 12 magnitude in the TESS band show a 3 sigma upper limit on the total change in brightness of less than half a percent on time scales between an hour and multiple weeks, empirically establishing their suitability as spectrophotometric standards. We further discuss the value and limits of high-cadence, high-precision photometric monitoring with TESS as a tool to vet the suitability of stars to act as spectrophotometric standards., Comment: 17 pages, 5 figures, 3 tables, accepted for publication by AAS Journals

We present a near-complete catalog of the metal-rich population of Thermally-Pulsing Asymptotic Giant Branch stars in the northwest quadrant of M31. This metal-rich sample complements the equally complete metal-poor Magellanic Cloud AGB catalogs produced by the SAGE program. Our catalog includes HST wide-band photometry from the Panchromatic Hubble Andromeda Treasury survey, HST medium-band photometry used to chemically classify a subset of the sample, and Spitzer mid- and far-IR photometry that we have used to isolate dust-producing AGB stars. We have detected 346,623 AGB stars; these include 4,802 AGB candidates producing considerable dust, and 1,356 AGB candidates that lie within clusters with measured ages, and in some cases metallicities. Using the Spitzer data and chemical classifications made with the medium-band data, we have identified both carbon- and oxygen-rich AGB candidates producing significant dust. We have applied color--mass-loss relations based on dusty AGB stars from the LMC to estimate the dust injection by AGB stars in the PHAT footprint. Applying our color relations to a subset of the chemically-classified stars producing the bulk of the dust, we find that ~97.8% of the dust is oxygen-rich. Using several scenarios for the dust lifetime, we have estimated the contribution of AGB stars to the global dust budget of M31 to be 0.9-35.5%, which is in line with previous estimates in the Magellanic Clouds. Follow-up observations of the M31 AGB candidates with the JWST will allow us to further constrain stellar and chemical evolutionary models, and the feedback and dust production of metal-rich evolved stars., Comment: Accepted for publication in ApJS. 35 pages, 25 Figures

We present infrared photometry of all 36 potential JWST calibrators for which there is archival Spitzer IRAC data. This photometry can then be used to inform stellar models necessary to provide absolute calibration for all JWST instruments. We describe in detail the steps necessary to measure IRAC photometry from archive retrieval to photometric corrections. To validate our photometry we examine the distribution of uncertainties from all detections in all four IRAC channels as well as compare the photometry and its uncertainties to those from models, ALLWISE, and the literature. 75% of our detections have standard deviations per star of all observations within each channel of less than three percent. The median standard deviations are 1.2, 1.3, 1.1, and 1.9% in [3.6] - [8.0] respectively. We find less than 8% standard deviations in differences of our photometry with ALLWISE, and excellent agreement with literature values (less than 3% difference) lending credence to our measured fluxes. JWST is poised to do ground-breaking science, and accurate calibration and cross-calibration with other missions will be part of the underpinnings of that science., Comment: 16 pages, 5 figures, AJ accepted

We produce a set of 72 NIR through UV extinction curves by combining new HST/STIS optical spectrophotometry with existing IUE spectrophotometry (yielding gapless coverage from 1150 to 10000 Angstroms) and NIR photometry. These curves are used to determine a new, internally consistent, NIR through UV Milky Way Mean Curve and to characterize how the shapes of the extinction curves depend on R(V). We emphasize that while this dependence captures much of the curve variability, there remains considerable variation which is independent of R(V). We use the optical spectrophotometry to verify the presence of structure at intermediate wavelength scales in the curves. The fact that the optical through UV portions of the curves are sampled at relatively high resolution makes them very useful for determining how extinction affects different broad band systems, and we provide several examples. Finally, we compare our results to previous investigations., Comment: To appear in The Astrophysical Journal

The Space Telescope Imaging Spectrograph (STIS) has measured the spectral energy distributions (SEDs) for several stars of types O, B, A, F, and G. These absolute fluxes from the CALSPEC database are fit with a new spectral grid computed from the ATLAS-APOGEE ATLAS9 model atmosphere database using a chi-square minimization technique in four parameters. The quality of the fits are compared for complete LTE grids by Castelli & Kurucz (CK04) and our new comprehensive LTE grid (BOSZ). For the cooler stars, the fits with the MARCS LTE grid are also evaluated, while the hottest stars are also fit with the NLTE Lanz & Hubeny OB star grids. Unfortunately, these NLTE models do not transition smoothly in the infrared to agree with our new BOSZ LTE grid at the NLTE lower limit of Teff =15,000K. The new BOSZ grid is available via the Space Telescope Institute MAST archive and has a much finer sampled IR wavelength scale than CK04, which will facilitate the modeling of stars observed by the James Webb Space Telescope (JWST). Our result for the angular diameter of Sirius agrees with the ground- based interferometric value., Comment: 11 figures

We present a new method for deriving the stellar birth function (SBF) of resolved stellar populations. The SBF (stars born per unit mass, time, and metallicity) is the combination of the initial mass function (IMF), the star-formation history (SFH), and the metallicity distribution function (MDF). The framework of our analysis is that of Poisson Point Processes (PPPs), a class of statistical models suitable when dealing with points (stars) in a multidimensional space (the measurement space of multiple photometric bands). The theory of PPPs easily accommodates the modeling of measurement errors as well as that of incompleteness. Compared to most of the tools used to study resolved stellar populations, our method avoids binning stars in the color-magnitude diagram and uses the entirety of the information (i.e., the whole likelihood function) for each data point; the proper combination of the individual likelihoods allows the computation of the posterior probability for the global population parameters. This includes unknowns such as the IMF slope and combination of SFH and MDF, which are rarely solved for simultaneously in the literature, however entangled and correlated they might be. Our method also allows proper inclusion of nuisance parameters, such as distance and extinction distributions. The aim of this paper, is to assess the validity of this new approach under a range of assumptions, using only simulated data. Forthcoming work will show applications to real data. Although it has a broad scope of possible applications, we have developed this method to study multi-band HST observations of the Milky Way Bulge. Therefore we will focus on simulations with characteristics similar to those of the Galactic Bulge., Comment: Accepted for publication in ApJ

We model multi-wavelength broadband UBVIJHKs and Spitzer IRAC and MIPS photometry and IRS spectra from the SAGE and SAGE-Spec observing programs of two oxygen-rich asymptotic giant branch (O-rich AGB) stars in the Large Magellanic Cloud (LMC) using radiative transfer models of dust shells around stars. We chose a star from each of the bright and faint O-rich AGB populations found by earlier studies of the SAGE sample in order to derive a baseline set of dust properties to be used in the construction of an extensive grid of radiative transfer models of the O-rich AGB stars found in the SAGE surveys. From the bright O-rich AGB population we chose HV 5715, and from the faint O-rich AGB population we chose SSTISAGE1C J052206.92-715017.6 (SSTSAGE052206). We found the complex indices of refraction of oxygen-deficient silicates from Ossenkopf et al (1992) and a "KMH"-like grain size distribution with gamma of -3.5, a_min of 0.01 microns, and a_0 of 0.1 microns to be reasonable dust properties for these models. There is a slight indication that the dust around the faint O-rich AGB may be more silica-rich than that around the bright O-rich AGB. Simple models of gas emission suggest a relatively extended gas envelope for the faint O-rich AGB star modeled, consistent with the relatively large dust shell inner radius for the same model. The models compute the dust mass-loss rates for the two stars to be 2.0x10^-9 M_Sun/yr and 2.3x10^-9 M_Sun/yr, respectively. When a dust-to-gas mass ratio of 0.002 is assumed for SSTSAGE052206 and HV 5715, the dust mass-loss rates imply total mass-loss rates of 1.0x10^-6 M_Sun/yr and 1.2x10^-6 M_Sun/yr, respectively. These properties of the dust shells and stars, as inferred from our models of the two stars, are found to be consistent with properties observed or assumed by detailed studies of other O-rich AGB stars in the LMC and elsewhere., Comment: 37 pages, 3 figures, appeared in the 10 June 2010 issue of the Astrophysical Journal

The measurement of precise absolute fluxes for stellar sources has been pursued with increased vigor since the discovery of the dark energy and the realization that its detailed understanding requires accurate spectral energy distributions (SEDs) of redshifted Ia supernovae in the rest frame. The flux distributions of spectrophotometric standard stars were initially derived from the comparison of stars to laboratory sources of known flux but are now mostly based on calculated model atmospheres. For example, pure hydrogen white dwarf (WD) models provide the basis for the HST CALSPEC archive of flux standards. The basic equations for quantitative spectrophotometry and photometry are explained in detail. Several historical lab based flux calibrations are reviewed; and the SEDs of stars in the major on-line astronomical databases are compared to the CALSPEC reference standard spectrophotometry. There is good evidence that relative fluxes from the visible to the near-IR wavelength of ~2.5 micron are currently accurate to 1% for the primary reference standards; and new comparisons with lab flux standards show promise for improving that precision., Comment: 56 pages, 22 figures, accepted for publication in PASP

The SAGE-Spectroscopy Spitzer legacy program (SAGE-Spec; PI: F. Kemper, PID: 40159; Kemper et al. 2010) is the IRS spectroscopic follow-up to the successful SAGE-LMC legacy program (Meixner et al. 2006; PI: M. Meixner, PID: 20203) that mapped the Large Magellanic Cloud (LMC) with all bands of the IRAC and MIPS instruments on board the Spitzer Space Telescope. This technical document gives details of the data-reduction procedure and the various data products that are publicly available through IRSA: http://irsa.ipac.caltech.edu/data/SPITZER/SAGE/, Comment: 40 pages, 1 figure, data delivery document to accompany the public release of SAGE-Spec data

We investigate the infrared (IR) properties of cool, evolved stars in the Small Magellanic Cloud (SMC), including the red giant branch (RGB) stars and the dust-producing red supergiant (RSG) and asymptotic giant branch (AGB) stars using observations from the Spitzer Space Telescope Legacy program entitled: "Surveying the Agents of Galaxy Evolution in the Tidally-stripped, Low Metallicity SMC", or SAGE-SMC. The survey includes, for the first time, full spatial coverage of the SMC bar, wing, and tail regions at infrared (IR) wavelengths (3.6 - 160 microns). We identify evolved stars using a combination of near-IR and mid-IR photometry and point out a new feature in the mid-IR color-magnitude diagram that may be due to particularly dusty O-rich AGB stars. We find that the RSG and AGB stars each contribute ~20% of the global SMC flux (extended + point-source) at 3.6 microns, which emphasizes the importance of both stellar types to the integrated flux of distant metal-poor galaxies. The equivalent SAGE survey of the higher-metallicity Large Magellanic Cloud (SAGE-LMC) allows us to explore the influence of metallicity on dust production. We find that the SMC RSG stars are less likely to produce a large amount of dust (as indicated by the [3.6]-[8] color). There is a higher fraction of carbon-rich stars in the SMC, and these stars appear to able to reach colors as red as their LMC counterparts, indicating that C-rich dust forms efficiently in both galaxies. A preliminary estimate of the dust production in AGB and RSG stars reveals that the extreme C-rich AGB stars dominate the dust input in both galaxies, and that the O-rich stars may play a larger role in the LMC than in the SMC., Comment: Accepted for publication in AJ. 25 pages, 36 figures, Table 4 will be available electronically from AJ

Fundamental parameters and time-evolution of mass loss are investigated for post-main-sequence stars in the Galactic globular cluster 47 Tucanae (NGC 104). This is accomplished by fitting spectral energy distributions (SEDs) to existing optical and infrared photometry and spectroscopy, to produce a true Hertzsprung--Russell diagram. We confirm the cluster's distance as 4611 (+213, -200) pc and age as 12 +/- 1 Gyr. Horizontal branch models appear to confirm that no more RGB mass loss occurs in 47 Tuc than in the more-metal-poor omega Centauri, though difficulties arise due to inconsistencies between the models. Using our SEDs, we identify those stars which exhibit infrared excess, finding excess only among the brightest giants: dusty mass loss begins at a luminosity of ~ 1000 Lsun, becoming ubiquitous above 2000 Lsun. Recent claims of dust production around lower-luminosity giants cannot be reproduced, despite using the same archival Spitzer imagery., Comment: 22 pages, 17 figures, accepted ApJS

We present the classification of 197 point sources observed with the Infrared Spectrograph in the SAGE-Spec Legacy program on the Spitzer Space Telescope. We introduce a decision-tree method of object classification based on infrared spectral features, continuum and spectral energy distribution shape, bolometric luminosity, cluster membership, and variability information, which is used to classify the SAGE-Spec sample of point sources. The decision tree has a broad application to mid-infrared spectroscopic surveys, where supporting photometry and variability information are available. We use these classifications to make deductions about the stellar populations of the Large Magellanic Cloud and the success of photometric classification methods. We find 90 asymptotic giant branch (AGB) stars, 29 young stellar objects, 23 post-AGB objects, 19 red supergiants, eight stellar photospheres, seven background galaxies, seven planetary nebulae, two HII regions and 12 other objects, seven of which remain unclassified., Comment: (43 pages, 21 figures, 4 tables including one large table out of order; to be published in MNRAS)

We present 52-93 micron spectra, obtained with the Spitzer Space Telescope, of luminous compact far-IR sources in the SMC. These comprise 9 Young Stellar Objects (YSOs), the compact HII region N81 and a similar object within N84, and two red supergiants (RSGs). The spectra of the sources in N81 (of which we also show the ISO-LWS spectrum between 50-170 micron) and N84 both display strong [OI] 63-micron and [OIII] 88-micron fine-structure line emission. We attribute these lines to strong shocks and photo-ionized gas, respectively, in a ``champagne flow'' scenario. The nitrogen content of these two HII regions is very low, definitely N/O<0.04 but possibly as low as N/O<0.01. Overall, the oxygen lines and dust continuum are weaker in star-forming objects in the SMC than in the LMC. We attribute this to the lower metallicity of the SMC compared to that of the LMC. Whilst the dust mass differs in proportion to metallicity, the oxygen mass differs less; both observations can be reconciled with higher densities inside star-forming cloud cores in the SMC than in the LMC. The dust in the YSOs in the SMC is warmer (37-51 K) than in comparable objects in the LMC (32-44 K). We attribute this to the reduced shielding and reduced cooling at the low metallicity of the SMC. On the other hand, the efficiency of the photo-electric effect to heat the gas is found to be indistinguishable to that measured in the same manner in the LMC, 0.1-0.3%. This may result from higher cloud-core densities, or smaller grains, in the SMC. The dust associated with the two RSGs in our SMC sample is cool, and we argue that it is swept-up interstellar dust, or formed (or grew) within the bow-shock, rather than dust produced in these metal-poor RSGs themselves. Strong emission from crystalline water ice is detected in at least one YSO. (abridged), Comment: Accepted for publication in The Astronomical Journal

[abridged] We present 52-93 micron spectra obtained with Spitzer in the MIPS-SED mode, of a representative sample of luminous compact far-IR sources in the LMC. These include carbon stars, OH/IR AGB stars, post-AGB objects and PNe, RCrB-type star HV2671, OH/IR red supergiants WOHG064 and IRAS05280-6910, B[e] stars IRAS04530-6916, R66 and R126, Wolf-Rayet star Brey3a, Luminous Blue Variable R71, supernova remnant N49, a large number of young stellar objects, compact HII regions and molecular cores, and a background galaxy (z~0.175). We use the spectra to constrain the presence and temperature of cold dust and the excitation conditions and shocks within the neutral and ionized gas, in the circumstellar environments and interfaces with the surrounding ISM. Evolved stars, including LBV R71, lack cold dust except in some cases where we argue that this is swept-up ISM. This leads to an estimate of the duration of the prolific dust-producing phase ("superwind") of several thousand years for both RSGs and massive AGB stars, with a similar fractional mass loss experienced despite the different masses. We tentatively detect line emission from neutral oxygen in the extreme RSG WOHG064, with implications for the wind driving. In N49, the shock between the supernova ejecta and ISM is revealed by its strong [OI] 63-micron emission and possibly water vapour; we estimate that 0.2 Msun of ISM dust was swept up. Some of the compact HII regions display pronounced [OIII] 88-micron emission. The efficiency of photo-electric heating in the interfaces of ionized gas and molecular clouds is estimated at 0.1-0.3%. We confirm earlier indications of a low nitrogen content in the LMC. Evidence for solid state emission features is found in both young and evolved object; some of the YSOs are found to contain crystalline water ice., Comment: Accepted for publication in The Astronomical Journal. This paper accompanies the Summer 2009 SAGE-Spec release of 48 MIPS-SED spectra, but uses improved spectrum extraction. (Fig. 2 reduced resolution because of arXiv limit.)

We investigate dust production and stellar mass loss in the Galactic globular cluster NGC 362. Due to its close proximity to the Small Magellanic Cloud (SMC), NGC 362 was imaged with the IRAC and MIPS cameras onboard the Spitzer Space Telescope as part of the Surveying the Agents of Galaxy Evolution (SAGE-SMC) Spitzer Legacy program. We detect several cluster members near the tip of the Red Giant Branch that exhibit infrared excesses indicative of circumstellar dust and find that dust is not present in measurable quantities in stars below the tip of the Red Giant Branch. We modeled the spectral energy distribution (SED) of the stars with the strongest IR excess and find a total cluster dust mass-loss rate of 3.0(+2.0/-1.2) x 10^-9 solar masses per year, corresponding to a gas mass-loss rate of 8.6(+5.6/-3.4) x 10^-6 solar masses per year, assuming [Fe/H] = -1.16. This mass loss is in addition to any dust-less mass loss that is certainly occurring within the cluster. The two most extreme stars, variables V2 and V16, contribute up to 45% of the total cluster dust-traced mass loss. The SEDs of the more moderate stars indicate the presence of silicate dust, as expected for low-mass, low-metallicity stars. Surprisingly, the SED shapes of the stars with the strongest mass-loss rates appear to require the presence of amorphous carbon dust, possibly in combination with silicate dust, despite their oxygen-rich nature. These results corroborate our previous findings in omega Centauri., Comment: 13 pages, 11 figures. Accepted to ApJ

We present empirical relations describing excess emission from evolved stars in the Large Magellanic Cloud (LMC) using data from the SAGE (Surveying the Agents of a Galaxy's Evolution) survey which includes the IRAC 3.6, 4.5, 5.8 and 8.0 \mu m and MIPS 24, 70 and 160 \mu m bands. We combine the SAGE data with the Two Micron All Sky Survey (2MASS; J, H and Ks) and the optical Magellanic Cloud Photometric Survey (MCPS; U, B, V and I) point source catalogs to create complete spectral energy distributions (SEDs) of the asymptotic giant branch (AGB) star candidates in the LMC. AGB star outflows are among the main producers of dust in a galaxy, and this mass loss results in an excess in the fluxes observed in the 8 and 24 \mic m bands. We identify oxygen-rich, carbon-rich and extreme AGB star populations in our sample based on their 2MASS and IRAC colors. We calculate excesses fluxes in the mid-IR bands by comparison of the SEDs with model photospheres. We find about 16,000 O-rich, 6300 C-rich and 1000 extreme sources with reliable 8 \mu m excesses, and about 4500 O-rich, 5300 C-rich and 960 extreme sources with reliable 24 \mic m excesses. The excesses are in the range 0.1 mJy--5 Jy. The 8 and 24 \mic m excesses for all three types of AGB candidates show a general increasing trend with luminosity. The dust color temperature derived from the ratio of the 8 and 24 \mic m excesses decreases with an increase in excess, while the 24 \mic m optical depth increases with excess. The extreme AGB candidates are the major contributors to the mass loss, and we estimate the total AGB mass-loss return to the LMC to be (5.9--13)\times 10^{-3} Msun yr^{-1}., Comment: 41 pages, 18 figures, accepted for publication in the Astronomical Journal