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Mikako MatsuuraNAOJ

Dusty disks in evolved stars?

Post-AGB (Asymptotic Giant Branch) starsPlanetary Nebulae (PNe)

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Main sequence

Red giant branch (RGB)

AGB

Post-AGB

Planetary nebula

Luminosity [Lsun]

Effective Temperature [K]

The evolutionary tracks of 1, 5 and 25 Msun stars on the HR diagram (Iben 1995)

What arepost-AGB stars,

planetary nebulae (PNe)?

Late stage of stellar evolution for low mass stars (1-8 Msun in main sequence)

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Some examples of unique shapes and

common-namesNGC 6537Spider Nebula

NGC 2392Eskimo Nebula

OH 231.8+4.2Rotten Egg Nebula

NGC 6542Cat’s Eye Nebula

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Current problems in the field of PNe research

Change in shapes

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Main Sequence

(MS)AGB stars

Planetary nebulae

(PNe)

1-8 Msun Central star: ~0.6 Msun

Mass loss

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Post-AGB stars and PNe

Post-AGB stars and PNeAsymmetric structureRoundEllipseBipolar

AGB stars : spherical symmetry

Balick & Frank (2002)

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Formation mechanisms of bipolar outflows

Circum(-binary) diskRemnant of AGB mass loss

Magnetic field

Troidal shaped AGB wind

Magnetic field

Balick & Frank (2002)

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Disk model

Hydrodynamic model by Icke (2003)

A warped disk

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Two casesNGC 6302 (Bug Nebula)OH 231.8+4.8 (Rotten Egg Nebula)

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Butterfly nebulaIcke’s model resemble to the shape of NGC 6302

About 8 arcsec disk?

Icke’s model Matsuura et al. (2005)

NGC 6302HST optical image

(H, NeII composite)

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Dense disc

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Optical three band composite image (HST)

Matsuura et al. (2005)

Extinction map A(H) [mag]H - 6cm

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JCMT 450 m image

Central core

Bipolar

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Lo

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Source of 450 m flux

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5 arcsec

6 cm image(free-free emission)

20 arcsec

CoreI450m=3Jy per beamI450m(ff)~0.4Jy per beam-> 450m dust excess

LobeI450m~1Jy per beamI450m(ff)<0.1Jy per beam

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Results for NGC 6302 study

A warped discExpanding discFormation mechanism of the disc

Circum(-binary) disc. Binary? Too large inner radius?

Magnetic field can form the bipolar, however, the presence of the disc is not necessary

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Compact disks

Icke’s model’s Too large disk compared with the size of outflow

In most of the case, disk is more compact, especially at early phase of post-AGB

HST Optical image of the post-AGB star, OH 231.8+4.2

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The post-AGB star, OH 231.8+4.2

HST optical imageRed: 791nm (cont.)

Green: 675 nm (cont.+ionise lines)

Blue: combination of Ha (656nm) and NeII (658nm)

Collimated outflow Shocked bubble Dense torus

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Infrared images of OH 231

Bujarrabal et al. (2002)

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Infrared images of OH 231

InfraredIonized linesLess dust extinction

Central region is more apparent

Very compact and bright object at the centre

Matsuura et al. ApJL accepted

ESO/VLT/NACO

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Infrared images of OH 231

11.7 micronJura et al. (2002)

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Very compact disk

Jura et al. (2002)’s fitting to SED

Compact diskThe emission from blackbody at 130 K from a cylinder of radius 5x1015 cm at a tilt angle of 54 degrees

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MIDI VLTI observations

MID-infrared Interferometric instrument (MIDI)

UT3 - UT4 62.4 metre baseline

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MIDI VLT observations

Observing logSmall angular informationVariation in projected length

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Spectra from MIDI

Spectra from MIDI

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Wavelength [micron]

Flu

x [J

y]

8 1310

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Visibilities (correlated flux)

00 .511 .52891 0111 21 3O B 1 (6 1 .7 m )O B 2 (5 8 .9 m )O B 3 (5 2 .8 m )O B 4 (4 7 .4 m )W a v e le n g th [m ic ro n ]

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Radius of the disk

Distance 1.3 kpc, member of open cluster M46 (Jura & Morris 1985)

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Model fit (preliminary)

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Comparison with other observations

MIDI : 40-50 AUSiO : 3 AU

MIDICircumstellar material (probably disk)

Not the central star

R(star) ~ 3 AUSanchez Contreras et al. (2002)

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Binary disk model

Binary with a separation of 10-100 AU

Binary disk may be formed

Mastrodemos & Morris (1999)

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Conclusion & Future work

Circumstellar material with a radius of 40-50 AU (upper limit)

Very compact: binary disk?

Future: measurements of visibilities in different uv-plane

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Model for far-infrared excess

Dust ~0.03Msun

Tdust<100K

1x1016cm < Rdust < 10x1016cm