The Red Rectangle

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The Red Rectangle

• Solid state components of varying composition in
  the outflow

Ciska Markwick-Kemper University of Virginia
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Astrochemistry Rosetta Stone

• Nearby post-AGB star seen edge-on
• Extended Red Emission, Diffuse Interstellar Bands
• Evolution and extent of PAHs
• Silicates crystalline and amorphous
• Mulas et al. (I.45)
• Topalovic Sarre (I.61)
• Song et al. (I.64)
• Vijh et al. (I.70)

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• ISO-SWS
• O-rich crystalline silicates in circumstellar
  disk
• C-rich PAHs in bipolar outflow (ground-based)
• Large beam!

Molster/Waters

• HST imaging
• Outflow is highly inhomogeneous
• Do the IR characteristics vary in the outflow?

Van Winckel/Cohen
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IRS high resolution pointings

• 30 away from central star
• D 710 pc

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IRS Spectra
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Features in the spectra
PAHs
PAHs

• Position 1 Position 4

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Features in the spectra

• PAHs Out-of-plane bending modes
• Broad features at gt13 micron
• Not PAH-related too strong compared to 11.3
  micron PAH feature
• Solid state carrier
• Changing composition or grain shape
• Little continuum
• High UV/optical opacity

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Simple oxides (Mg,Fe)O

• Position 1 pixel 1 Mg0.6Fe0.4O

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Simple oxides Fe content

• Position 4 triple pixel extraction

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Identification

• Features at gt17 micron (Mg,Fe)O
• D710 pc Tdust 75 K, Mdust 10-5 M?
• D500 pc Tdust 150 K, Mdust Mmoon
• Features between 13-16 micron
• Spinel
• UV/optical opacity is low, grain temperature
  remains too low
• (Fe,Mg)O / silicate mixture
• Silicates are more complex condensates
• Correlation with gt17 micron feature?
• Correlation with ERE?
• Instrumental artefacts

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O-rich dust in the outflow

• Previous consensus disk contains O-rich dust
  (silicates), outflow is C-rich (PAHs)
• This detection O-rich dust in outflow
• Relic from early mass loss? Primitive, low
  density condensates
• Erosion from circumstellar disk? But where are
  the silicates?
• What causes the varying composition in the
  outflow?
• Evidence for PAHs in the disk (ground-based Vijh
  et al.)

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Current challenges

• Spectral maps in the Low Resolution mode of
  Spitzer-IRS
• MIR features extent, variation, nature and are
  they artefacts?
• Extent and variation of PAHs
• High sensitivity detections 1 arcmin from
  center
• Data reduction not trivial ?

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www.TheRedRectangle.net

• Charlottesville, Virginia, USA
• 23-25 May, 2006
• Lou Allamandola Jan Cami Martin Cohen
• Ciska Markwick-Kemper Hans Van Winckel
• Andrew Markwick-Kemper

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The Red Rectangle

• In relatively rare post-AGB phase
• Nearby (710 pc) and well studied
• Stellar parameters HD 44179, B9-A0 III
  L? 6050 L?, T? 7750 K, R? 43 R?
• Only stellar source with Extended Red Emission
  (ERE)
• Circumstellar environment mixed chemistry
  oxygen-rich disk, carbon-rich outflow