Recent results from the SIMECA code and the VLTI observations Anthony Meilland and Philippe Stee...

Recent results from the SIMECA code and Recent results from the SIMECA code and the VLTI observationsthe VLTI observations

Anthony Meilland and Philippe SteeAnthony Meilland and Philippe SteeObservatoire de la Côte d’AzurObservatoire de la Côte d’Azur

I. Active Hot StarsI. Active Hot Stars

II. The SIMECA CodeII. The SIMECA Code

III. Modelling The VLTI dataIII. Modelling The VLTI dataα α Ara with MIDI Ara with MIDI

α α Ara with AMBERAra with AMBERMWC297 with AMBERMWC297 with AMBERHD50013 with AMBERHD50013 with AMBER

IV. ConclusionIV. Conclusion

What Are Active Hot Stars ?What Are Active Hot Stars ?

-Hot :-Hot :Spectral Type O B A Spectral Type O B A Teff > 8000 K Teff > 8000 K

-Active :-Active :Emission lines, IR excess ,Envelope or disc, gaz or\and dust, Emission lines, IR excess ,Envelope or disc, gaz or\and dust, Pulsations and other VariabilityPulsations and other Variability


A huge variety of phenomena !A huge variety of phenomena !


-Fast Rotation : 60-80% of the critical velocity-Fast Rotation : 60-80% of the critical velocity(nearly 100% for Achernar)(nearly 100% for Achernar)

-Stellar Wind : Radiatively driven, with high velocity-Stellar Wind : Radiatively driven, with high velocity

-Binarity : Interaction with a companion, mass transfer -Binarity : Interaction with a companion, mass transfer

-Pulsation : Non radial, many modes measured-Pulsation : Non radial, many modes measured

-Magnetism : few hundred Gauss recently measured-Magnetism : few hundred Gauss recently measured

A huge variety of geometry and Kinematics !A huge variety of geometry and Kinematics !

-Envelope shape : Spherical, flattened, thick or thin disc, ring, jets-Envelope shape : Spherical, flattened, thick or thin disc, ring, jets

-Opacity : optically thin, thick or between -Opacity : optically thin, thick or between

-Inhomogeneities : outbursts, blobs, arms, holes …-Inhomogeneities : outbursts, blobs, arms, holes …

-Rotation law : Keplerian, angular momentum conservation …-Rotation law : Keplerian, angular momentum conservation …

-Radial velocity : None, expansion, accretion or both …-Radial velocity : None, expansion, accretion or both …

-Polar component of the velocity : Wind Compressed disc-Polar component of the velocity : Wind Compressed disc


A huge variety of stars !A huge variety of stars !


-Be : Main sequence stars, ionised hydrogen disc, stellar wind-Be : Main sequence stars, ionised hydrogen disc, stellar wind

-Herbig Ae\Be : Young stars, dust accretion disc, stellar windHerbig Ae\Be : Young stars, dust accretion disc, stellar wind

-B[e] : super-giant stars, stellar wind, dust discB[e] : super-giant stars, stellar wind, dust disc

-Wolf Rayet : Strong mass loss, No photospheric line (optical thick Wolf Rayet : Strong mass loss, No photospheric line (optical thick wind)wind)

……And even some more violent objects like the monster Eta Car !!And even some more violent objects like the monster Eta Car !!

SIMulation d’Etoiles Chaudes ActiveSIMulation d’Etoiles Chaudes Active

Developed by Stee (1995)Developed by Stee (1995)Stee and Bittar (2001) Stee and Bittar (2001)

Stee and Meilland (2004)Stee and Meilland (2004)

A physical model : A physical model : Hydrodynamics (CAK wind model) Hydrodynamics (CAK wind model)

and radiative transfer (in Sobolev approximation)and radiative transfer (in Sobolev approximation) in a rotating and expanding gaz envelopein a rotating and expanding gaz envelope

Made for interpretation of observations :Made for interpretation of observations :Compute photometric (SED), spectroscopic (line profiles) Compute photometric (SED), spectroscopic (line profiles)

and interferometric (intensity mapsand interferometric (intensity mapsvisibility curves) observablesvisibility curves) observables

II. The SIMECA codeII. The SIMECA code

Star and envelope physical parameters :

Temperature Equatorial terminal velocityStellar radius Polar terminal velocity Photospheric density Polar mass fluxRotational velocity Equatorial/polar mass flux ratioInclination H/H+He

“Free parameters”

m1: Exponent of the mass flux variation lawm2: Exponent of the velocity variation law

Enter parameters :


Hydrodynamic :ρ, Vr, VФ, 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



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 :

Aik, Bic et Ci : absorption, spontaneous emission and recombination coefficient βik : 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

)(2

1

1

1eie

ikikkik

i

kicickiiki TCnAnBAn





Transfer equationIn the continuum

Transfer equationIn 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-BoundIn 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)

Idz

dI





Line Profiles

Intensity mapsIn the lines

Intensity maps in the continuum

Spectral Energy Distribution

Enter parameters :




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 integrationIntensity maps in the continuum





Line Profiles

MapsIn the lines

Maps in the continuum

Spectral EnergyDistribution

Enter parameters :





Actual and Future developmentsActual and Future developments

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

Future : Future : -Radiative transfer without Sobolev approximation (with Daniela Korkacova -Radiative transfer without Sobolev approximation (with Daniela Korkacova code)code)-Asymmetry in the envelope (Real 3D code without axisymmetry)-Asymmetry in the envelope (Real 3D code without axisymmetry)-Real dynamics-Real dynamics


The VLTIThe VLTI

- Baseline from few meters up to - Baseline from few meters up to 200 m200 m- Good (u,v) plane coverage- Good (u,v) plane coverage (if you manage to have time and (if you manage to have time and telescopes!!)telescopes!!)

Two InstrumentsTwo Instruments MIDIMIDI

Mid-infrared ( 2 spectral bandwidths )Mid-infrared ( 2 spectral bandwidths )8-13 mm and 13-26 mm8-13 mm and 13-26 mm2 telescopes2 telescopesVisibility modulus and differential phaseVisibility modulus and differential phaseLow spectral resolution ( R≈200)Low spectral resolution ( R≈200)Maximum spatial resolution of 12 mas @ 10 Maximum spatial resolution of 12 mas @ 10 μμmm

Be studies:Be studies:- Observation of a Ara during SDT ( June 2003)- Observation of a Ara during SDT ( June 2003)with HD 316285 (N=9.2, unresolved)with HD 316285 (N=9.2, unresolved)and d Cen (N=15, unresolved) in June 2004 and d Cen (N=15, unresolved) in June 2004 with UT1-UT3 B =103m)with UT1-UT3 B =103m)

AMBERAMBER Near infrared Near infrared 1-2.5 mm1-2.5 mm3 telescopes3 telescopesVisibility modulus, differential phase, phase closureVisibility modulus, differential phase, phase closureSpectral resolution : R = 10000Spectral resolution : R = 10000Maximum spatial resolution of 2,5 mas @ 2 Maximum spatial resolution of 2,5 mas @ 2 μμmm

Be studies :Be studies :- Specially designed for stellar envelopes - Specially designed for stellar envelopes - Kinematics studies- Kinematics studies- Numerous faint objects- Numerous faint objects- Already guarantee time dedicated to Be stars Already guarantee time dedicated to Be stars

4 Telescopes:4 Telescopes:UT Fixed D=8,2mUT Fixed D=8,2m

4 Auxiliary Telescopes 4 Auxiliary Telescopes AT moveables D=1,6mAT moveables D=1,6m

III. Modelling the VLTI dataIII. Modelling the VLTI data

B3VneB3Vne

mmVV=2.8=2.8

mmKK=3.8=3.8

Teff = 18000 KTeff = 18000 K

RR** = 4.8 R = 4.8 Roo

MM** = 9.6 M = 9.6 Moo

Vsin i = 220km/sVsin i = 220km/s

Distance : 74 pc Distance : 74 pc

Polarization : 172°Polarization : 172°

αα Ara with MIDI Ara with MIDIPublished In A&A in 2005Published In A&A in 2005

““First VLTI\MIDI observation of a Be star : First VLTI\MIDI observation of a Be star : αα Arae” Arae”Chesneau, Meilland, Rivinius, Stee et al.Chesneau, Meilland, Rivinius, Stee et al.


VLTI data obtained in June 2003 and Spectrum from Brazil in august 2003VLTI data obtained in June 2003 and Spectrum from Brazil in august 2003

Spectral Energy Distribution : Spectral Energy Distribution :

(8-13.5 mm) (8-13.5 mm)

Pa b line profile:Pa b line profile:

(1,28 mm, transition 5-3)(1,28 mm, transition 5-3)

Visibilities as a function of l (8-13.5 mm) :Visibilities as a function of l (8-13.5 mm) :

june, 17 : B=79 m , PA = 55°june, 17 : B=79 m , PA = 55°june, 16 : B=102 m , PA = 7°june, 16 : B=102 m , PA = 7°

αα Ara with MIDI Ara with MIDIIII. Modelling the VLTI dataIII. Modelling the VLTI data

FEROS data obtained in may 1999 (Thomas Rivinius)FEROS data obtained in may 1999 (Thomas Rivinius)

(transition 2-3)(transition 2-3) (transition 2-4)(transition 2-4)


HHαα EW variations between 1978 and 2003 EW variations between 1978 and 2003


Physical Parameters determinationPhysical Parameters determination

Fit of the HFit of the H & H & H lines (1999) lines (1999)

Few parameters variables:Few parameters variables:density, wind velocity, envelope extensiondensity, wind velocity, envelope extension

Fit of the Paschen Fit of the Paschen (2003) (2003)

Agreement between observed and simulated visibilities?Agreement between observed and simulated visibilities?

HH line profile variation between 1978 & 1999 line profile variation between 1978 & 1999Timescale around 7 yearsTimescale around 7 years

Circumstellar disk variationsCircumstellar disk variationsbetween 1999 & 2003between 1999 & 2003

Two groups from non simultaneousTwo groups from non simultaneousSpectroscopic and interferometric dataSpectroscopic and interferometric data

May 1999 & Summer 2003May 1999 & Summer 2003

Continuum supposed constant betweenContinuum supposed constant between1999 & 20031999 & 2003

αα Ara’s SED Ara’s SED

ResultsResults αα Ara’s distance Ara’s distance

From Cohen et al. 2001 :From Cohen et al. 2001 :122 pc122 pc

Fluxes & Color indicesFluxes & Color indices

Problem :Problem :Mismatch between the two ditances determination.Mismatch between the two ditances determination.

Not possible for a B3Vne to have a radius less than 5 RNot possible for a B3Vne to have a radius less than 5 Roo

From Hipparcos :From Hipparcos :74 pc74 pc

ParallaxParallax

SIMECA :SIMECA :Flux depends on the star radius and distance (Radius used : 4.8 RFlux depends on the star radius and distance (Radius used : 4.8 Roo))

Distance obtained: 105 pcDistance obtained: 105 pc

74 pc

105 pc

Maybe a (unseen) companion can produce a wrong Hipparcos parallaxMaybe a (unseen) companion can produce a wrong Hipparcos parallax

or Error from Cohen et al. (2001) estimationor Error from Cohen et al. (2001) estimation

HH & H & Hfitsfits

Input ParametersInput Parameters

RR**=5R=5Roo

Teff = 18000KTeff = 18000Kphotphot=1.2 10=1.2 10-12 -12

VVphotphot = 0.08 = 0.08VVrot rot = 300 km/s= 300 km/s

= 0.86= 0.86PolePole = 1.7 10 = 1.7 10-9-9

m1 = 0.3m1 = 0.3m2 = 0.45m2 = 0.45C1 = 30 C1 = 30

VVpôlepôle = 2000 km/s = 2000 km/sVVeqeq = 180 km/s = 180 km/s

i = 45°i = 45°

Nearly spherical Nearly spherical

Inclination Inclination V Vrotrot

Strong polar windStrong polar wind

Low equatorial windLow equatorial wind

Fit of the Paschen Fit of the Paschen line lineand visibilitiesand visibilities

Variations ?Variations ?

densitydensity Envelope Envelope GeometryGeometry

WindsWinds

FlatteningFlattening inhomogeneitiesinhomogeneities Troncated diskTroncated disk

Variations & parametersVariations & parameters

RRmaxmax decreases by 18% (R decreases by 18% (Rmax max = 82.7R= 82.7R**))

decreases by 25% (decreases by 25% (photphot=0.97 10=0.97 10-12-12))

Problems with the visibilities fitsProblems with the visibilities fits

Decrease of the envelopeDecrease of the envelopeextensionextension

(4,5 times ≈ 22 R(4,5 times ≈ 22 R**))++

Constant Flux Constant Flux (density increase)(density increase)

Best Scenario:Best Scenario:Disk troncature by aDisk troncature by a

close companionclose companion

Ara’s Binarity = Ara’s Binarity = tau tau ??

Period : 70 daysPeriod : 70 daysOrbital radius : 32 ROrbital radius : 32 R**

Masse of the companion : Masse of the companion : <2M<2Moo

AMBER Observations : PaAMBER Observations : Pa & Br & BrBaseline : 20 up to 100 mBaseline : 20 up to 100 m

Avoid P.A. ≈ 12°Avoid P.A. ≈ 12°

Amber Br γ line profile (not calibrated)

This emission line is produced within the Circumstellar envelope

αα Ara with AMBER Ara with AMBER(Preliminary work)(Preliminary work)


AMBER visibility Theoretical visibilitiesusing the SIMECA code

αα Ara with AMBER Ara with AMBERIII. Modelling the VLTI dataIII. Modelling the VLTI data

AMBER phase Theoretical phase using the SIMECA code

αα Ara with AMBER Ara with AMBERIII. Modelling the VLTI dataIII. Modelling the VLTI data

MWC297MWC297 with AMBER with AMBER(work in progress)(work in progress)


MWC297 : MWC297 : Herbig Be starHerbig Be starStrong hydrogen line in emission (Hα = 120 and Hβ=11)Strong hydrogen line in emission (Hα = 120 and Hβ=11)Star + Accretion disc + WindStar + Accretion disc + Wind

Accretion disc + Star: Code by Fabien Malbet Accretion disc + Star: Code by Fabien Malbet Wind : Modified version of SIMECAWind : Modified version of SIMECA ( with the opacity and emission from the accretion disc)( with the opacity and emission from the accretion disc)

Data :Data :-Flux and visibility in the K band with Mid resolution-Flux and visibility in the K band with Mid resolution-Br γ line profile with quite high resolution (ISAAC)-Br γ line profile with quite high resolution (ISAAC)-Hα and Hβ line profile from Drew’s 1999 article Hα and Hβ line profile from Drew’s 1999 article -Magnitudes and ISO spectra Magnitudes and ISO spectra

MWC297MWC297 with AMBER with AMBERIII. Modelling the VLTI dataIII. Modelling the VLTI data

Problem : Where is the Wind ?Problem : Where is the Wind ?In the equatorial plan ? At the pole? Near the star ?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 Quasi spherical wind, high velocity in the pole (600km\s), low velocity at the interface with the disc (70km\s)with the disc (70km\s)

Br Br γ emission zone : starts at 8Rγ emission zone : starts at 8R ends at 50Rends at 50R 8 with a maximum around 27R8 with a maximum around 27R


Problem : Differences between the 3 studied linesProblem : Differences between the 3 studied lines

Hα and Hβ profiles are very large (up to 600km\s)Hα and Hβ profiles are very large (up to 600km\s)Br Br γ profile is quite narrow (less than 200km\s)γ profile is quite narrow (less than 200km\s)

They comes from slightly different regionsThey comes from slightly different regions

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 =22500KRadius = 6 R Distance = 242 parsecs

Classical Be star IR excess :Beginning at 2μm

Spectral Energy Distribution (SED)

HD50013HD50013 with AMBER (preliminary work) with AMBER (preliminary work)III. Modelling the VLTI dataIII. Modelling the VLTI data

HD50013HD50013 with AMBER with AMBERIII. Modelling the VLTI dataIII. Modelling the VLTI data

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

Total = Star + free-free + free-bound

Fit of the SED with the SIMECA codeFit of the SED with the SIMECA code

Star = Planck


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. 1992 ApJ Supp. 81, 335

Hydrogen (+ He and Fe) lines in emission=

Circumstellar matter

Asymmetric profiles

Wine bottle or double peaks

Long-term variations


Visibility ModulusSpectrum

Differential phase Closure phase


Visibility Modulus

HD 50013 SIMECA 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


Visibility Phase

HD 50013 SIMECA 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. ConclusionIV. Conclusion

-Need of lot of data to constrain models:Need of lot of data to constrain models:Simultaneous and time series with various timescales Simultaneous and time series with various timescales each kind of data constrains some parameterseach kind of data constrains some parameters

photometric photometric density, mass flux (and star parameters) density, mass flux (and star parameters)interferometric interferometric geometry (+ kinematics if differential) geometry (+ kinematics if differential)spectroscopic spectroscopic kinematics ( + geometry ) kinematics ( + geometry )

- Need of two kind of model :Need of two kind of model :Physical but simple enough to be fast = SIMECAPhysical but simple enough to be fast = SIMECA

+ non-axisymmetric + dynamics (for + non-axisymmetric + dynamics (for inhomogeneity)inhomogeneity)More complex with less approximations (Sobolev)More complex with less approximations (Sobolev)

to test the limits of the SIMECA code to test the limits of the SIMECA code Slower Slower can’t be use easily to model observations can’t be use easily to model observations

Recent results from the SIMECA code and the VLTI observations Anthony Meilland and Philippe Stee...

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Transcript of Recent results from the SIMECA code and the VLTI observations Anthony Meilland and Philippe Stee...