Recent results from the SIMECA code and the VLTI observations Anthony Meilland and Philippe Stee Observatoire de la Côte d’Azur

I. Active Hot Stars II. The SIMECA Code III. Modelling The VLTI data α Ara with MIDI α Ara with AMBER MWC297 with AMBER HD50013 with AMBER IV. Conclusion

What Are Active Hot Stars ? -Hot : Spectral Type O B A  Teff > 8000 K -Active : Emission lines, IR excess,Envelope or disc, gaz or\and dust, Pulsations and other Variability I. Active Hot Stars

A huge variety of phenomena ! I. Active Hot Stars -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

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 I. Active Hot Stars

A huge variety of stars ! I. Active Hot Stars -Be : Main sequence stars, ionised hydrogen disc, stellar wind -Herbig Ae\Be : Young stars, dust accretion disc, stellar wind -B[e] : 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 !!

SIMulation d’Etoiles 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 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 II. The SIMECA code

Star and envelope physical parameters : TemperatureEquatorial terminal velocity Stellar radiusPolar terminal velocity Photospheric densityPolar mass flux Rotational velocity Equatorial/polar mass flux ratio InclinationH/H+He “Free parameters” m1: Exponent of the mass flux variation law m2: Exponent of the velocity variation law Enter parameters : II. The SIMECA code

Hydrodynamic : ρ, V r, V Ф, T Enter parameters : Starting with the basic hydrodynamic equations : -Continuity equation -Mass conservation equation -No energy conservation (we don’t know the heating processes) -Perfect gaz equation With few hypothesis : -axial symmetry (no azimuthal dependency) -Stationarity -Temperature 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 II. The SIMECA code

Hydrodynamic : ρ, V r, V Ф, T Statistic equilibrium: n1,…,n7,ne at LTE n1,…,n7,ne non-LTE Enter parameters : We start with at the LTE (Level 1 to 7 + continuum) Using the Sobolev approximation (high velocity gradient) we obtain the statistic equilibrium equation : A ik, B ic et C i : absorption, spontaneous emission and recombination coefficient β ik : 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 II. The SIMECA code

Hydrodynamic : ρ, V r, V Ф, 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 Enter parameters : Radiative transfer equation : τ calculated by integration: dτ =-κ. 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 : - κ and ε 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) II. The SIMECA code

Hydrodynamic : ρ, V r, V Ф, T Statistic equilibrium: n1,…,n7,ne at LTE n1,…,n7,ne non-LTE Line Profiles Intensity maps In the lines Intensity maps in the continuum Spectral Energy Distribution Enter parameters : Transfer equation In the continuum Transfer equation In the lines Transfer equation in the contiuum 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 Intensity maps in the continuum II. The SIMECA code

Hydrodynamic : ρ, V r, V Ф, T Statistic equilibrium: n1,…,n7,ne at LTE n1,…,n7,ne non-LTE Line Profiles Maps In the lines Maps in the continuum Spectral Energy Distribution Enter parameters : Transfer equation In the continuum Transfer equation In the lines Transfer equation in the contiuum 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 II. The SIMECA code

The VLTI - Baseline from few meters up to 200 m - Good (u,v) plane coverage (if you manage to have time and telescopes!!) (if you manage to have time and telescopes!!) Two Instruments MIDI Mid-infrared ( 2 spectral bandwidths ) 8-13 mm and mm 2 telescopes Visibility modulus and differential phase Low spectral resolution ( R≈200) Maximum spatial resolution of μm Be studies: - Observation of a Ara during SDT ( June 2003) with HD (N=9.2, unresolved) and d Cen (N=15, unresolved) in June 2004 with UT1-UT3 B =103m) AMBER Near infrared mm 3 telescopes Visibility modulus, differential phase, phase closure Spectral resolution : R = Maximum spatial resolution of 2,5 2 μm Be studies : - Specially designed for stellar envelopes - Kinematics studies - Numerous faint objects - Already guarantee time dedicated to Be stars 4 Telescopes: UT Fixed D=8,2m 4 Auxiliary Telescopes AT moveables D=1,6m III. Modelling the VLTI data

B3Vne m V =2.8 m K =3.8 Teff = K R * = 4.8 R o M * = 9.6 M o Vsin i = 220km/s Distance : 74 pc Polarization : 172° α Ara with MIDI Published In A&A in 2005 “First VLTI\MIDI observation of a Be star : α Arae” Chesneau, Meilland, Rivinius, Stee et al. III. Modelling the VLTI data

VLTI data obtained in June 2003 and Spectrum from Brazil in august 2003 Spectral Energy Distribution : ( mm) Pa b line profile: (1,28 mm, transition 5-3) Visibilities as a function of l ( mm) : june, 17 : B=79 m, PA = 55° june, 16 : B=102 m, PA = 7° α Ara with MIDI III. Modelling the VLTI data

FEROS data obtained in may 1999 (Thomas Rivinius) (transition 2-3) (transition 2-4) α Ara with MIDI III. Modelling the VLTI data

Hα EW variations between 1978 and 2003 Hα EW variations between 1978 and 2003 α Ara with MIDI III. Modelling the VLTI data

Physical Parameters determination Fit of the H  & H  lines (1999) Few parameters variables: density, wind velocity, envelope extension Fit of the Paschen  (2003) Agreement between observed and simulated visibilities? H  line profile variation between 1978 & 1999 Timescale around 7 years Circumstellar disk variations between 1999 & 2003 Two groups from non simultaneous Spectroscopic and interferometric data May 1999 & Summer 2003 Continuum supposed constant between 1999 & 2003

α Ara’s SED

Results α Ara’s distance From Cohen et al : 122 pc Fluxes & Color indices Problem : Mismatch between the two ditances determination. Not possible for a B3Vne to have a radius less than 5 R o From Hipparcos : 74 pc Parallax SIMECA : Flux depends on the star radius and distance (Radius used : 4.8 R o ) Distance obtained: 105 pc 74 pc 105 pc Maybe a (unseen) companion can produce a wrong Hipparcos parallax or Error from Cohen et al. (2001) estimation or Error from Cohen et al. (2001) estimation

H  & H  fits Input Parameters R * =5R o Teff = 18000K  phot = V phot = 0.08 V rot = 300 km/s  = 0.86  Pole = m1 = 0.3 m2 = 0.45 C1 = 30 V pôle = 2000 km/s V eq = 180 km/s i = 45° Nearly spherical Inclination  V rot Strong polar wind Low equatorial wind

Fit of the Paschen  line and visibilities Variations ? density EnvelopeGeometry Winds Flatteninginhomogeneities Troncated disk Variations & parameters

R max decreases by 18% (R max = 82.7R * ) R max decreases by 18% (R max = 82.7R * )  decreases by 25% (  phot = )

Problems with the visibilities fits Decrease of the envelope extension (4,5 times ≈ 22 R * ) + Constant Flux (density increase) Best Scenario: Disk troncature by a close companion close companion  Ara’s Binarity =  tau ? Period : 70 days Orbital radius : 32 R * Masse of the companion : <2M o AMBER Observations : Pa  & Br  Baseline : 20 up to 100 m Avoid P.A. ≈ 12°

Amber Br γ line profile (not calibrated) This emission line is produced within the Circumstellar envelope α Ara with AMBER (Preliminary work) III. Modelling the VLTI data

AMBER visibility Theoretical visibilities using the SIMECA code α Ara with AMBER III. Modelling the VLTI data

AMBER phase Theoretical phase using the SIMECA code α Ara with AMBER III. Modelling the VLTI data

MWC297 with AMBER (work in progress) III. Modelling the VLTI data MWC297 : Herbig Be star Strong hydrogen line in emission (Hα = 120 and Hβ=11)  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) ( with the opacity and emission from the accretion disc) Data : -Flux and visibility in the K band with Mid resolution -Br γ line profile with quite high resolution (ISAAC) -Hα and Hβ line profile from Drew’s 1999 article -Magnitudes and ISO spectra

MWC297 with AMBER III. Modelling the VLTI data 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 γ emission zone : starts at 8R  ends at 50R  8 with a maximum around 27R 

MWC297 with AMBER III. Modelling the VLTI data Problem : Differences between the 3 studied lines Hα and Hβ profiles are very large (up to 600km\s) Br γ profile is quite narrow (less than 200km\s) They comes from slightly different regions

MWC297 with AMBER III. Modelling the VLTI data

Flux from SIMBAD : Magnitudes U,B,V,R,I,J,H,K,L,M + UV Flux ( μm) + ISO Flux μm + 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) HD50013 with AMBER (preliminary work) III. Modelling the VLTI data

HD50013 with AMBER III. Modelling the VLTI data Free-Free and Free- Bound emission from the circumstellar envelope : Inclination = 45° Density at the photosphère = g.cm -3 Mass loss = M  \year Total = Star + free-free + free-bound Fit of the SED with the SIMECA code Star = Planck

HD50013 with AMBER III. Modelling the VLTI data Line profiles H  H  FeII 5317 A HeI 5876 A Dachs et al. 1992, A&AS, 95, 437 H  H  H  From Lenorzer A. et al. 2002, A&A, 384, 473 Slettebak et al ApJ Supp. 81, 335 Hydrogen (+ He and Fe) lines in emission = Circumstellar matter Asymmetric profiles Wine bottle or double peaks Long-term variations

HD50013 with AMBER III. Modelling the VLTI data Visibility ModulusSpectrum Differential phaseClosure phase

HD50013 with AMBER III. Modelling the VLTI data Visibility Modulus HD 50013SIMECA simulation for a classical Be star Visibility variation in the line (Hα) for a classical Be star for different rotational velocity law (Constant, keplerian, angluar momentum conservation…) Asymmetric Visibility modulus variation in the Br γ 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

HD50013 with AMBER III. Modelling the VLTI data Visibility Phase HD 50013SIMECA simulation for a classical Be star No phase variation in the Br γ line = Circumstellar matter dominated by radial movement = No Rotation ? ! Phase variation in the line (Hα) for different rotational velocity law (Constant, keplerian, angluar momentum conservation…)

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  can’t be use easily to model observations  Slower  can’t be use easily to model observations