Recent results from the SIMECA code and the VLTI observations

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Recent results from the SIMECA code and the VLTI
observations
Anthony Meilland and Philippe SteeObservatoire
de la Côte dAzur
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I. Active Hot Stars II. The SIMECA Code III.
Modelling The VLTI data a Ara with MIDI a Ara
with AMBER MWC297 with AMBER HD50013 with
AMBER IV. Conclusion
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I. Active Hot Stars
What Are Active Hot Stars ?
-Hot Spectral Type O B A ? Teff gt 8000 K
-Active Emission lines, IR excess ,Envelope or
disc, gaz or\and dust, Pulsations and other
Variability
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I. Active Hot Stars
A huge variety of phenomena !
-Fast Rotation 60-80 of the critical
velocity (nearly 100 for Achernar) -Stellar
Wind Radiatively driven, with high
velocity -Binarity Interaction with a
companion, mass transfer -Pulsation Non
radial, many modes measured -Magnetism few
hundred Gauss recently measured
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I. Active Hot Stars
A huge variety of geometry and Kinematics !
-Envelope shape Spherical, flattened, thick or
thin disc, ring, jets -Opacity optically thin,
thick or between -Inhomogeneities outbursts,
blobs, arms, holes -Rotation law
Keplerian, angular momentum conservation
-Radial velocity None, expansion, accretion
or both -Polar component of the velocity
Wind Compressed disc
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I. Active Hot Stars
A huge variety of stars !

• -Be Main sequence stars, ionised hydrogen disc,
  stellar wind
• Herbig Ae\Be Young stars, dust accretion disc,
  stellar wind
• Be super-giant stars, stellar wind, dust disc
• Wolf Rayet Strong mass loss, No photospheric
  line (optical thick wind)
• And even some more violent objects like the
  monster Eta Car !!

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II. The SIMECA code
SIMulation dEtoiles Chaudes Active
Developed by Stee (1995) Stee and Bittar (2001)
Stee and Meilland (2004)
A physical model Hydrodynamics (CAK wind
model) and radiative transfer (in Sobolev
approximation) in a rotating and expanding gaz
envelope
Made for interpretation of observations Compute
photometric (SED), spectroscopic (line profiles)
and interferometric (intensity maps?visibility
curves) observables
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II. The SIMECA code
Star and envelope physical parameters
Temperature Equatorial terminal
velocity Stellar radius Polar terminal velocity
Photospheric density Polar mass flux Rotational
velocity Equatorial/polar mass flux
ratio Inclination H/HHe Free
parameters m1 Exponent of the mass flux
variation law m2 Exponent of the velocity
variation law
Enter parameters
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II. The SIMECA code
Starting with the basic hydrodynamic equations
-Continuity equation -Mass conservation
equation -No energy conservation (we dont know
the heating processes) -Perfect gaz
equation With few hypothesis -axial symmetry
(no azimuthal dependency) -Stationarity -Temperatu
re depending only on r -No polar component of the
velocity in the envelope We obtain in the
envelope the distribution of -Density -Radial
and azimuthal velocity -Temperature
Enter parameters
Hydrodynamic ?, Vr, V?, T
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II. The SIMECA code
We start with at the LTE (Level 1 to 7
continuum) Using the Sobolev approximation (high
velocity gradient) we obtain the statistic
equilibrium equation Aik, Bic et Ci
absorption, spontaneous emission and
recombination coefficient ßik Escape
probability (depend on the velocity
gradient) We calculate the level population from
this equations and the previous calculated
values.. We iterate until the convergence of the
values of the ni
Enter parameters
Hydrodynamic ?, Vr, V?, T
Statistic equilibrium n1,,n7,ne at LTE
n1,,n7,ne non-LTE
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II. The SIMECA code
Radiative transfer equation t calculated by
integration dt -? . dz (along the line of sight
) In the Continuum -Opacity of the envelope
Free-Free emission and electronic
diffusion -Emissivity of the envelope Free-Free
and Free-Bound In the Lines - ? and e
expression for the selected transition -Sobolev
approximation Intensity function of the
spatial variables (perpendicularly to the line of
sight) for a transition (line) or function
to the wavelength (continuum)
Enter parameters
Hydrodynamic ?, Vr, V?, T
Statistic equilibrium n1,,n7,ne at LTE
n1,,n7,ne non-LTE
Transfer equation In the continuum
Transfer equation In the lines
Transfer equation in the contiuum
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II. The SIMECA code
In the line Calculation of the zone of
projected iso-velocity ? Doppler shift -Spatial
integration Line profile -Spectral
integration (with a given spectral
band) Intensity maps in the line In the
continuum -Spatial integration Spectral
Energy Distribution -Spectral integration Intensi
ty maps in the continuum
Enter parameters
Hydrodynamic ?, Vr, V?, T
Statistic equilibrium n1,,n7,ne at LTE
n1,,n7,ne non-LTE
Transfer equation In the continuum
Transfer equation In the lines
Transfer equation in the contiuum
Line Profiles
Intensity maps in the continuum
Spectral Energy Distribution
Intensity maps In the lines
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II. The SIMECA code
Enter parameters
Hydrodynamic ?, Vr, V?, T
Statistic equilibrium n1,,n7,ne at LTE
n1,,n7,ne non-LTE
Transfer equation In the continuum
Transfer equation In the lines
Transfer equation in the contiuum
Line Profiles
Maps in the continuum
Spectral Energy Distribution
Maps In the lines
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II. The SIMECA code
Actual and Future developments

• Actual
• -More levels for the free-bound emission (for
  MIDI data)
• Ring and truncated disc model (evolution of the
  envelope)
• -Interfacing with an accretion disc model
  (opacity of the dust)
• -Asymmetry in the envelope

Future -Radiative transfer without Sobolev
approximation (with Daniela Korkacova
code) -Asymmetry in the envelope (Real 3D code
without axisymmetry) -Real dynamics
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III. Modelling the VLTI data
The VLTI
4 Telescopes UT Fixed D8,2m
4 Auxiliary Telescopes AT moveables D1,6m
- Baseline from few meters up to 200 m - Good
(u,v) plane coverage (if you manage to have time
and telescopes!!)
Two Instruments
MIDI
AMBER
Mid-infrared ( 2 spectral bandwidths ) 8-13 mm
and 13-26 mm 2 telescopes Visibility modulus and
differential phase Low spectral resolution (
R200) Maximum spatial resolution of 12 mas _at_ 10
µm Be studies - Observation of a Ara during SDT
( June 2003) with HD 316285 (N9.2,
unresolved) and d Cen (N15, unresolved) in
June 2004 with UT1-UT3 B 103m)

• Near infrared
• 1-2.5 mm
• 3 telescopes
• Visibility modulus, differential phase, phase
  closure
• Spectral resolution R 10000
• Maximum spatial resolution of 2,5 mas _at_ 2 µm
• Be studies
• - Specially designed for stellar envelopes
• - Kinematics studies
• - Numerous faint objects
• Already guarantee time dedicated to Be stars

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III. Modelling the VLTI data
a Ara with MIDI Published In AA in 2005 First
VLTI\MIDI observation of a Be star a
Arae Chesneau, Meilland, Rivinius, Stee et al.
B3Vne mV2.8 mK3.8 Teff 18000 K R 4.8 Ro M
9.6 Mo Vsin i 220km/s Distance 74 pc
Polarization 172
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III. Modelling the VLTI data
a Ara with MIDI
VLTI data obtained in June 2003 and Spectrum
from Brazil in august 2003
Visibilities as a function of l (8-13.5 mm)
june, 17 B79 m , PA 55
june, 16 B102 m , PA 7
Spectral Energy Distribution (8-13.5
mm)
Pa b line profile (1,28 mm, transition
5-3)
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III. Modelling the VLTI data
a Ara with MIDI
FEROS data obtained in may 1999 (Thomas Rivinius)
(transition 2-3)
(transition 2-4)
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III. Modelling the VLTI data
a Ara with MIDI
Ha EW variations between 1978 and 2003
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Physical Parameters determination
Ha line profile variation between 1978
1999 Timescale around 7 years
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a Aras SED
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Results
a Aras distance
From Cohen et al. 2001 122 pc Fluxes Color
indices
From Hipparcos 74 pc Parallax
SIMECA Flux depends on the star radius and
distance (Radius used 4.8 Ro) Distance
obtained 105 pc

74 pc 105 pc
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Ha Hb fits
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Variations parameters
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Problems with the visibilities fits
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III. Modelling the VLTI data
a Ara with AMBER (Preliminary work)
Amber Br ? line profile (not calibrated) This
emission line is produced within the
Circumstellar envelope
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III. Modelling the VLTI data
a Ara with AMBER
Theoretical visibilities using the SIMECA code
AMBER visibility
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III. Modelling the VLTI data
a Ara with AMBER
Theoretical phase using the SIMECA code
AMBER phase
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III. Modelling the VLTI data
MWC297 with AMBER (work in progress)

• MWC297
• Herbig Be star
• Strong hydrogen line in emission (Ha 120 and
  Hß11)
• Star Accretion disc Wind
• Accretion disc Star Code by Fabien Malbet
• Wind Modified version of SIMECA
• ( with the opacity and emission from the
  accretion disc)
• Data
• -Flux and visibility in the K band with Mid
  resolution
• -Br ? line profile with quite high resolution
  (ISAAC)
• Ha and Hß line profile from Drews 1999 article
  
• Magnitudes and ISO spectra

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III. Modelling the VLTI data
MWC297 with AMBER

• Problem Where is the Wind ?
• In the equatorial plan ? At the pole? Near the
  star ?
• Quasi spherical wind, high velocity in the pole
  (600km\s), low velocity at the interface with the
  disc (70km\s)
• Br ? emission zone starts at 8R? ends at 50R?
  8 with a maximum around 27R?

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III. Modelling the VLTI data
MWC297 with AMBER
Problem Differences between the 3 studied
lines Ha and Hß profiles are very large (up to
600km\s) Br ? profile is quite narrow (less than
200km\s) They comes from slightly different
regions
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III. Modelling the VLTI data
MWC297 with AMBER
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III. Modelling the VLTI data
HD50013 with AMBER (preliminary work)
Flux from SIMBAD Magnitudes U,B,V,R,I,J,H,K,L,M
UV Flux (0.2-0.4µm) ISO Flux
10-30-60-100µm Radio measurements
Star B1.5IVe Planck function with Teff
22500K Radius 6 R? Distance 242 parsecs
Classical Be star IR excess Beginning at 2µm
Spectral Energy Distribution (SED)
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III. Modelling the VLTI data
HD50013 with AMBER
Fit of the SED with the SIMECA code
Total Star free-free free-bound
Star Planck
Free-Free and Free- Bound emission from the
circumstellar envelope Inclination
45 Density at the photosphère 10 -13 g.cm
-3 Mass loss 10-9 M?\year
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III. Modelling the VLTI data
HD50013 with AMBER
Line profiles
          H?                  H?                H
?
Hydrogen ( He and Fe) lines in
emission Circumstellar matter
    H?    H?   FeII l 5317 A   HeI l 5876 A  
Dachs et al. 1992, AAS, 95, 437
Asymmetric profiles Wine bottle or double peaks
Long-term variations
From Lenorzer A. et al. 2002, AA, 384, 473
Slettebak et al. 1992 ApJ Supp. 81, 335
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III. Modelling the VLTI data
HD50013 with AMBER
Visibility Modulus
Spectrum
Differential phase
Closure phase
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III. Modelling the VLTI data
HD50013 with AMBER
Visibility Modulus
HD 50013
SIMECA simulation for a classical Be star
Asymmetric Visibility modulus variation in the Br
? line Red part of the emission in the line is
more resolved than in the continuum, but blue
part is less resolved Inhomogeneity in a
rotating envelope (cf one-armed oscillations
Berio et al. 1999) ? Need of an asymmetric
model
Visibility variation in the line (Ha) for a
classical Be star for different rotational
velocity law (Constant, keplerian, angluar
momentum conservation)
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III. Modelling the VLTI data
HD50013 with AMBER
Visibility Phase
HD 50013
SIMECA simulation for a classical Be star
No phase variation in the Br ? line
Circumstellar matter dominated by radial
movement No Rotation ? !
Phase variation in the line (Ha) for different
rotational velocity law (Constant, keplerian,
angluar momentum conservation)
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IV. Conclusion

• Need of lot of data to constrain models
• Simultaneous and time series with various
  timescales
• each kind of data constrains some parameters
• photometric ? density, mass flux (and star
  parameters)
• interferometric ? geometry ( kinematics if
  differential)
• spectroscopic ? kinematics ( geometry )

• Need of two kind of model
• Physical but simple enough to be fast SIMECA
• non-axisymmetric dynamics (for
  inhomogeneity)
• More complex with less approximations (Sobolev)
• to test the limits of the SIMECA code
• ? Slower ? cant be use easily to model
  observations