Spitzer's view on mass-losing AGB stars

About 16 Spitzer satellite programs from the Guaranteed Time or the first cycle of Open Time, investigate AGB stars or related objects in different environments like the Magellanic Clouds and our Galaxy. Main objectives of these programs are to investigate the composition of the dust in the circumstellar environment and the effect of mass loss on the AGB evolution.

Spitzer offers the first opportunity to perform such studies on different populations and so to investigate the effects of, for instance, metallicity on the grain formation or on the amount of mass loss occurring on the AGB.

We expect that the main fraction of observations of the different projects will have been performed by now and that soon the first results will be published. It seems a good time (a few months before the deadline for the next cycle of Spitzer observing time) to bring representatives from the different teams together in a workshop where current results could be discussed, papers finalized within teams, collaboration/pooling of results between teams could be discussed, and future observations planned. The following topics would be addressed:

* data reduction, errors, artefacts,...

* Presentation of results:

  - Spectra for LMC, Bulge, SMC,...

  - Modelling of the spectra...

  - Mass loss rates, central star properties, dust properties ...

* Missing data, follow-up observations, collaborations

Overview of Spitzer programs:

PI                         instr                     Title

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Blommaert         IRS                      The dust sequence along the AGB

Bobrowsky         IRS                      Galactic Bulge Planetary Nebulae as Probes of Stellar Evolution

Egan                   IRS                      Dusty Evolved Stars in the SMC

Hony                    IRS                      Detatched Shells Around Carbon-Stars

Houck                 IRS                      IRS Study of Planetary Nebulae in the SMC/LMC

Houck                 IRS                      Circumstellar Dust in the Magellanic Clouds

Kastner               IRS                      The Spitzer IRS Spectral Atlas of infrared-Luminous Evolved Stars in the LMC

Kemper              IRS                      The composition and evolution of dust in astrophysical environments

Kemper              IRS                      The O-rich condensation sequence at low metallicity: LMC AGB and post-AGB stars

Lebzelter            IRS                      Revealing the Nature of Mass Loss in Globular Cluster Stars

Morris                 MIPS                   The Progression of Mass-Loss During the AGB Star->Planetary Nebula Transition

Onaka                 IRS                      Time Variation Observations of Mid-Infrared Spectra of Mira Variables in NEP and LMC

Sahai                  IRAC/MIPS         Mass Loss from Galactic Bulge Giants: Probing Stellar and Galactic Evolution

Van Wincke       IRS                      Dusty discs around binary post-AGB stars and their relation to protoplanetary discs

Waelkens           IRS                      The composition and evolution of circumstellar dust from AGB to post-AGB and PNe phases

Wood                  IRS                      Mass loss from red giants: its development, dust properties, and dependence on the stellar parameters mass, luminosity and metallicity