2. Armando DOMICIANO de SOUZA Main collaborators: O. Chesneau (OCA, F), T. Driebe (MPIfR, D), K-.H. Hofmann (MPIfR, D), S. Kraus (MPIfR, D), A. Miroshnichenko (UT, US), K. Ohnaka (MPIfR, D), P. Stee (OCA, F), G. Weigelt (MPIfR, D)

3. Plan Introduction The B[e] phenomenon Principles of optical/IR long baseline interferometry VLTI (MIDI and AMBER) observations of CPD-57 2874 VLTI-MIDI (visibilities, spectrum, modelling, comparison to other data) VLTI-AMBER (visibilities, modelling, phases) Comparison of VLTI-MIDI and VLTI-AMBER results

4. The B[e] phenomenon (Lamers et al. 1998) 1. Strong Balmer emission lines. 2. Low excitation permitted emission lines of predominantly low ionization metals in the optical spectrum, e.g. Fe II. 3. Forbidden emission lines of [Fe II] and [O I] in the optical spectrum. 4. A strong near or mid-infrared excess due to hot circumstellar dust. Meilland

5. The B[e] phenomenon (Lamers et al. 1998) Zickgraf et al. (1985) Supergiants B[e]  L * /Lsun > 10 4 Observations point towards asymmetrical stellar environments Need for direct measurements  High angular resolution 

6. Principles of optical/IR long baseline interferometry Weigelt et al. (2003) IOTA spectro-interferometry Bands J H K

7. Principles of optical/IR long baseline interferometry Complex Visibilities V(u,v, )= FT[I(u,v, )] / FT[I(0,0, )] Weigelt et al. (2000) GI2T -  Cas Interference fringes  Intensity map I(y,z, )

8. Interferometry : the uv or Fourier plane ESO-VLTI Partial uv coverage  Models are needed to interpret the current interferometric observations u and v  spatial frequency B proj / ASPRO - JMMC Complex Visibility V(u,v, ) Fourier Transform Intensity distribution of the object at a given

9. Observations of B[e] stars with VLTI-MIDI and VLTI-AMBER Targets: GG Car MIDI Not well resolved (size < 10 mas) CPD-57 2874 MIDI and AMBER Observational set-up: MIDI N band with R=30 (8-13  m) Unit Telescopes (UTs) 2 baselines AMBER K band with R=1200 (2.1-2.2  m) Unit Telescopes (UTs) 3 baselines (closure phase)

10. VLTI-MIDI observations MIDI Equivalent uniform disc model: V( ) = |2J 1 (z) / z|, where z =   UD ( ) B proj /

11. VLTI-MIDI observations UD diameter versus Position Angle

12. VLTI-MIDI : fit of V with gaussian-models 2a = 2a 0 + K ( - 0 ) VLTI-MIDI : fit of V with gaussian-models Chromatic variation of the major axis FWHM  2a = 2a 0 + K ( - 0 ) Gaussian circle Gaussian ellipse 2a = (10.1  0.7) + (2.6  0.4) ( -8  m) mas Axial ratio 2b/2a = 0.76  0.08 Position angle PA = 144°  6° 2a = (15.3  0.7) + (0.5  0.2) ( -12  m) mas Axial ratio 2b/2a = 0.80  0.06 Position angle PA = 143°  6° 2a = (8.7  0.4) + (2.2  0.3) ( -8  m) mas 2a = (13.5  0.2) + (0.4  0.2) ( -12  m) mas

13. VLTI-MIDI spectrum Possible origin of this featureless spectrum around 10  m: Large grains ? Carbonaceous dust ? Free-free emission ? Additional opacity sources ?

14. Modelling VLTI-MIDI observations Envelope of dust with spherical symmetry DUSTY code (Ivezic et al.) Stellar input parameters: distance = 2 kpc V = 10.1 Av = 5.9  V 0 = 4.2 T eff = 20000 K log L/L  = 5.6 R = 53R   angular diameter Ø = 0.25 mas

15. Spherical model (DUSTY code) : silicate with large grains

17. Spherical model (DUSTY code) : graphite with large grains

19. Dust close to the star ? SED can be reproduced by the spherical dust model, but not the visibilities  inner dust radius is too large (~12 mas for silicates and ~60 mas for graphite) ! What is the origin of the mid-IR emission relatively close to the star measured with VLTI-MIDI ? Possibility to get dust closer to the star : Dense equatorial wind  disk-like structure able to shield the disk material to allow molecules and dust to be formed near the hot central star (Kraus & Lamers 2003).

20. Support for a non-spherical envelope A spherical model does not seem to simultaneously fit the SED and VLTI-MIDI visibilities Winds of sgB[e] have two components (e.g. Zickgraf et al. 1985) Several sgB[e] show high intrinsic polarizations consistent with non-spherical dusty envelopes (e.g. Magalhães 1992) Zickgraf et al. (1985)

21. Polarization PA versus VLTI-MIDI PA UBV Data from Yudin & Evans (1998) Yudin & Evans (1998) polarization = 45°  3° Polarization perpendicular to disc: (45°  3°) + 90°= 135  3° Ellipse orientation from MIDI : 143.5°  6° N E

22. VLTI-AMBER observations Equivalent uniform disc model: V( ) = |2J 1 (z) / z|, where z =   UD ( ) B proj / AMBER

23. VLTI-AMBER observations UD diameter versus Position Angle

24. VLTI-AMBER : fit of V with gaussian-models Gaussian ellipse 2a = (3.90  0.03) + (7.3  0.2) ( -2.2  m) mas Axial ratio 2b/2a = 0.56  0.01 Position angle PA = -2.9°  0.4° Br   C = 0.93  0.11 mas ;  =1.6  0.2 10 -3  m Gaussian circle 2a = (2.46  0.01) + (5.2  0.1) ( -2.2  m) mas Br   C = 0.64  0.08 mas ;  =1.6  0.2 pm Chromatic variation of the major axis FWHM : 2a=2a 0 +K( - 0 )+C exp[-4ln2( - c )/] 2a=2a 0 +K( - 0 )+C exp[-4ln2( - c )/  ]

25. VLTI-AMBER : closure phase closure phase (deg) VLTI  (microns) Centrally-symmetric intensity distribution

26. VLTI-AMBER : differential phases  (microns) Differential phase  (microns) VLTI UT2-UT3 UT3-UT4 UT4-UT2 No chromatic variation of object’s symmetry

27. Measured sizes of CPD-57 2874 N E AMBERMIDI

28. FIN THE END FIM ENDE

29. Interstellar polarization ? Stars within 2° of CPD-57 2874 (Heiles 2000) Stars with low and high polarizations have random PA

30. Modelling VLTI-MIDI observations Inner radius Silicate r in =12 mas ~100R * ~ 24 AU Graphite r in =60 mas ~480R * ~ 120 AU

31. g eff -effect  -effect bi-stable winds Lamers model Maeder model  Car van Boekel (2003) VLTI-VINCI Theory of (anisotropic) winds of massive stars Maeder & Desjacques (2001 A&A), Lamers & Pauldrach (1991 A&A), Maeder (1999 A&A), Langer et al. (1999 ApJ), etc von Zeipel effect: Rapid rotation and Log L/L  > 10 4  Star close to the  -limit : Eddington factor variable in latitude Mass loss variable in latitude (opacity and gravity effect) :