Interferometric observations
of post-AGB binaries
Eric J. Bakker
Leiden Observatory
Acknowledges: Rens Waters, Christoph Leinert, Uwer Graser, Walter
Jaffe, Bruno Lopez, Guy Perrin
Outline
• Post-AGB binaries
– photosphere
– binarity
– related objects
– models
• Interferometric observations on
– HR 4049
– Red Rectangle
• Interpretation
Red Rectangle
HR 4049
Van Winckel H., Mathis J.S., Waelkens C., 1992, Nature 356, 500
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AC Her
• Interstellar medium
• Post-AGB binaries <[Fe/H]>=-3.6
• Type II Cepheids <[Fe/H]>=-1.3:
• RV Tauri stars
• W Virginis star
• lambda Boötes stars <[Fe/H]>=-1.7
Van Winckel H., Mathis J.S., Waelkens C., 1992, Nature 356, 500
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Log L = 3.8 Lsun
R = 47 Rsun
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Teff = 7500 K
Log g = 1.0 cm/s2
[Fe/H] = -4/5
D = 667 Pc
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HR 4049
P
s
KA
e
f(m)
HR 4049
430.66 +- 0.28
−32.07 +- 0.13
15.96 +- 0.19
0.30 +- 0.01
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Red Rectangle
319 +- 3
0.37
0.052
days orbital period
km/s systemic velocity
km/s velocity amplitude primary
eccentricity
mass function
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Infrared Excess and
Infrared Spectrum
HR 4049
T star = 7500 K
T disk= 1150 K
PAH features
7.7, 8.6 and 11.3 micron
Dominik et al.
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Beintema et al. 1996
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Interaction binaries
category of post-AGB stars
• Red Rectangle
• HR 4049
• HD 56126
• HD 52961
• BD +39°4926
• HD 46703
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• etc.
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HR 4049 Radiative Transfer Model: disk height: H/R=1/3
disk radius: 8.5-20 AU
Extended thick disk
Central star, obscured by disk
Optically thick inner edge
Dominik et al. 2003, Image from Dullemond (PC)
The Red Rectangle
Circumbinary disk
Bipolar outflow
Hubble image: Cohen M., Van Winckel H., Bond H.E., Gull T.R., 2004, AJ 127, 2362
HST image of RR
Cohen, van Winckel, Bond, Gull, ApJ, 127:2362–2377, 2004
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Interferometric observations
• HR 4049 VLTI/VINCI
– 2002+2003: 28 exposures: B3-C3/D1-B3
– projected baselines 7 and 24 meter
• HR 4049 VLTI/MIDI
– February 4+7 & June 3, 2004: UT2-UT3
– GRISM, projected baseline 45 meter
• Red Rectangle VLTI/MIDI
– February 9, 2004: UT2-UT3
– GRISM, projected baseline 43 m
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MIDI
VINCI
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The HR 4049 case
• Classified as a post-AGB star
• Metal depleted photospheric abundance
• Binary orbit
• Infrared excess
• Roche Lobe overflow
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MIDI acquisition images
HR 4049
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Calibrator
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MIDI acquisition images contour plot
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VINCI data of HR 4049
37 milli-arcseconds best fit
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MIDI data of HR 4049
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Model fitting for HR 4049
•Continuum
• 30-40 milli-arcsec
•PAH
• 50-60 milli-arcsec
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New results on HR 4049
•
•
•
•
•
37 milli-arcsecond for disks
No indication of strong asymmetry
PAH emission from extended region
Tdust= 1150 K from SED
Emitting surface would give a K-band
flux a factor 6 too high.
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PAH emission
N
Central star
Disk at 870 K
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The Red Rectangle case
• Classified as a post-AGB star
• Metal depleted photospheric abundance
• Edge on binary orbit
• Infrared excess
• Roche Lobe overflow
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Red Rectangle acquisition images
Red Rectangle
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Calibrator
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MIDI acquisition images contour plot
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MIDI data on the Red Rectangle
Baseline
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MIDI data on the Red Rectangle
Looks like a Silicate feature
or a reversed PAH spectrum
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Silicate features or PAH
or something else ?
Miyata, A&A 415, 179–187, 2004
Speck, Barlow, Sylvester, and
Hofmeister, AAS 146, 437, 2000
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New results on Red Rectangle
• The PAH emission for the Red Rectangle seems
to be absent in the central region. Hence it
originates from large distance
• There seems to be a silicate feature or an
inversed PAH spectrum in the visibility curve of
the Red Rectangle.
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Overall conclusions
1. VLTI observations give unique
information on the geometry of the
circumstellar environment
2. Spectral information versus continuum
information provide additional constrains
3. Data seem to indicate a three component
model: for HR 4049: star+disk+lobes
4. Data seem to indicate a silicate feature in
the central region of the Red Rectangle
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Announcements
VLTI/MIDI data reduction, analysis and science school
11-15 October 2004, Leiden Observatory
http://www.strw.leidenuniv.nl/~nevec/workshop_2004/
OPTICON Network Activity Interferometry
Exchange program on optical interferometry
3000 Euro for a 1 month exchange visit
Deadline 15 September 2004
http://www.strw.leidenuniv.nl/~eurinterf
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END
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