Spitzer Space Telescope - Guaranteed Time Observer Proposal #40115


Dual dust chemistry in Wolf-Rayet Planetary Nebulae

Principal Investigator: Giovanni Fazio
           Institution: Harvard-Smithsonian Center for Astrophysics

     Technical Contact: Joseph Hora, Harvard-CfA

Co-Investigators: 
Joseph Hora, CfA                                                      
Martin Cohen, Univ. California - Berkeley                             
Michael Barlow, University College London                             
Paul Crowther, University of Sheffield, UK                            
Quentin Parker, Macquarie University Australia                        

Science Category: evolved stars/pn/sne 
 Observing Modes: IracMap IrsStare 
  Hours Approved: 14.9 

Abstract:
Wolf-Rayet central stars of planetary nebulae are rare H-deficient stars. The
mid-infrared spectra of planetary nebula central stars of late WC type
([WC8-12]) reveal dual dust chemistry: polycyclic aromatic hydrocarbons and
crystalline silicates and water ice. We will use the Spitzer Space Telescope to
help answer a fundamental question about planetary nebulae containing Wolf-Rayet
stars: do all these nebulae show the simultaneous presence of carbon- and
oxygen-rich molecules and dust in their MIR spectra, regardless of stellar
spectral type, and does this phenomenon relate to the evolution of these
planetaries? We will address this question through IRS low- and high-resolution
spectra of the nebulae and their stars spanning the full range of Wolf-Rayet
spectral types of the central stars. To interpret the nebular slit spectra we
will image the PNe with IRAC in HDR mode. Well-calibrated spectra will help to
understand the origin of these rare nebulae and may indicate whether evolution
alone dictates their morphology, spectral energy distributions, dust band
strengths, mass-loss history, and the mid-infrared spectra of their central
stars.