Spitzer Space Telescope - General Observer Proposal #30666


Mass Loss from Classical Cepheids and their Progenitors

Principal Investigator: Nancy Evans
           Institution: Smithsonian Astrophysical Observatory

Co-Investigators: 
Pauline Barmby, SAO                                                   
Massimo Marengo, SAO                                                  
Guiseppe Bono, INAF-Osservatorio Astronomico di Roma                  
Douglas Welch, McMaster University                                    
Martino Romaniello, ESO                                               

Science Category: massive stars 
 Observing Modes: IracMap MipsPhot 
  Hours Approved: 15.4 

Abstract:
Classical Cepheid variable stars are primary extragalactic distance
indicators, so accurately understanding and modeling them is vital.
There remains a discrepancy between measured masses and masses from
evolutionary and pulsation calculations, as evidenced by the recent
results on Polaris.  One possible explanation is mass loss.  The
current proposal is to observe a sample of Cepheids with Spitzer in
order to determine whether mass loss is the explanation or whether
adjustment to the physics of the computations is needed.  The target
list includes stars with a range in mass, luminosity, pulsation
amplitude, and binary status, all of which could influence the level
of mass loss.  Spitzer observations have the spatial resolution to
isolate any Cepheid emission from that of nearby stars or the
background.Spectral energy distributions from Spitzer data should
fully address the question of mass loss.