20-23 March 2006 - VIRA - Paris High Resolution Imaging of dust disks structures around Herbig Ae stars with VISIR C.Doucet, P-O Lagage, E. Pantin (CEA Saclay SAp) E. Habart (IAS, Orsay) C. Pinte, G. Duchêne, F. Ménard (LAOG, Grenoble)

VISIR VLT Imager and Spectrometer for the InfraRed Located at the Cassegrain focus of UT3 of the VLT. 2 bands IR of obervations: N Band : 8 - 13 μm Q Band : 17 - 24 μm Spatial resolution: 15 times the ones of ISOCAM or Spitzer (0.075 ’’/pixel) Spectral resolution: 350 - 25000 at 10 μm 1200 - 12500 at 20 μm.

New imaging mode: BURST mode Seeing not as good as expected → lost spatial resolution 0.8’’ seeing Seeing of 0.8’’ in the visible →Seeing of 0.4’’ in mid-IR →movement of 5 pixels. → Limit the effect of TURBULENCE by freezing the atmosphere with very short exposure time :BURST MODE

Speckle in mid-IR Texposition ~ 16-50 (ms) ≤ T0(mid-IR) D~R0 In Near-IR In Mid-IR wavelength SEEING 0.5’’ 1’’ (µm) R0 (m) T0(ms) 2 1.05 52-210 0.52 28-100 10 7.28 360-1450 3.64 200-700 20 16.7 835-3340 8.36 400-1600 Wind speed between 5 and 20 m/s Texposition ~ 16-50 (ms) ≤ T0(mid-IR) → Stable atmosphere D~R0 → One principal speckle

BURST: turbulence effect Sensibility ↔ 14 mJy/10σ/1h Sensibility ↔ 7 mJy/10σ/1h Reference star HD85503 at 11.3 µm (January 2005)

Image quality/shift and add in mid-IR HD62902 at 11.3 µm, Seeing of 1.2’’ in the visible HD85503 at 11.3 µm (January 2005, seeing of 0.75’’ in the visible) Shift and add by centroid Shift and add by autocorrelation Shift and add by maximum FWHMx (mas) 358 300 437 FWHMy (mas) 552 542 ellipticity 1.54 1. 1.24 Strehl ratio 0.27 0.80 0.67 Shift and add by centroid Shift and add by autocorrelation Shift and add by maximum FWHMx (mas) 424 302 386 FWHMy (mas) 547 288 523 ellipticity 1.29 0.95 1.36 Strehl ratio 0.328 0.760 0.368

Limit of the method For bright sources (5 Jy in N band) Method shift and add valid for a seeing ≤ 1.3’’ in the visible Otherwise → speckle interferometry Effect of a bad seeing (1.5 ’’) on the source

A star noticeable: HD97048 a Herbig A star at 180 pc in the Chameleon cloud PAH stochastically heated by UV radiation from the star Could allow to see the disk much further from the star: new TRACERS of the disk geometry Doucet et al. 2006,submitted A&A

What could we learn from PAH emission? First measure of the height versus the radius H ∞ R1.5

Conclusions/Perspectives HD169142 in mode normal (PAH1, 8.6 µm) 0.65 ’’ seeing, exposure time: 316 s HD169142 in BURST mode (PAH1, 8.6 µm) 0.55’’ seeing, exposure time: 118 s Sometimes, elongated source TRUST in BURST mode planned to be a technical mode Work with ESO to open this mode to community PSF substracted

Modelisation of a flared disk Model of disk heated by irradiation from the central star, in hydrostatic equilibrium in the vertical direction, with dust and gaz well mixed, with transiently heated small grains and PAHs addition to large grains in thermal equilibrium (1-D radiation transfert code, Habart et al. 2004).