atmospheric dynamics of red supergiant stars

11

Atmospheric dynamics of red supergiant stars

Andrea ChiavassaGroupe de Recherche en Astronomie et

Astrophysique du LanguedocGRAAL

Thesis advisor: Bertrand Plez

22

OutlineOutline

RSG starsRSG stars The modeller's point of view The modeller's point of view The virtual observer’s point of viewThe virtual observer’s point of view SpectroscopySpectroscopy InterferometryInterferometry Conclusions et perspectivesConclusions et perspectives

33

OutlineOutline


44

RSG stars - 1RSG stars - 1

Meynet & Maeder, 2003

RRSG 500 - 1000 Rsun

10 < MRSG < 30 Msun

3450 K < TRSG < 4100K(Levesque et al., 2005)

55


RSGs:RSGs:

- are irregular, small-are irregular, small-amplitude variablesamplitude variables

- strong molecular bands - strong molecular bands (TiO ...)(TiO ...)

- broad lines (vmacrobroad lines (vmacro10 10 km/s, Josselin et Plez km/s, Josselin et Plez 2004)2004)

continuum poorly continuum poorly defined, spectrum defined, spectrum synthesis is difficult ... synthesis is difficult ...

TimeVis

mag

Flu

x (a

rbit

rary

un

its)

AAVSO

66


Profiles are variable in depth, width and velocity !

(stronger variations are seen in other RSG).

Time-variable structure in line profiles is a natural and necessary consequence of giant convective cells

Josselin & Plez, 2007

77


Young et al. 2000

Bright spot model for 700 nm (TiO)

mas

mas

QuickTime™ e undecompressore TIFF (Non compresso)

sono necessari per visualizzare quest'immagine.

Haubois et al. 2006H band - IONIC

QuickTime™ e undecompressore TIFF (Non compresso)


Alpha Ori is big and relatively nearby. Excellent target for Interferometry

Surface inhomogeneitiesSurface inhomogeneities Parametric models not enough to Parametric models not enough to

explain physicsexplain physics Need for more complicated Need for more complicated

models?models?

HST - Faint Object CameraUV

88

And the answers to RSG And the answers to RSG questions?questions?

COCO55BOLD (COnservative COde for the COmputation of BOLD (COnservative COde for the COmputation of COmpressible COnvection in a BOx of L Dimensions, COmpressible COnvection in a BOx of L Dimensions, l=2,3) developed by Freytag, Steffen, Ludwig et al. (l=2,3) developed by Freytag, Steffen, Ludwig et al. ( for for RSG, RSG, Freytag et al., 2002; 2008 in prep.))

Key point: coupling of radiation and hydrodynamics, Key point: coupling of radiation and hydrodynamics, which dominates in the physics of the transition layerswhich dominates in the physics of the transition layers

This tool will help to investigate:This tool will help to investigate:1.1. the nature of the convection patternthe nature of the convection pattern2.2. the atmospheric velocity fieldsthe atmospheric velocity fields3.3. the impact of convection on spectral lines, visibility the impact of convection on spectral lines, visibility

curves and phasescurves and phases

99

OutlineOutline


1010

The modeller's point of view, The modeller's point of view, COCO55BOLDBOLD - 1 - 1

QuickTime™ e undecompressore TIFF (LZW)sono necessari per visualizzare quest'immagine.

STAR-IN-A-BOX setup:

• Used to model RSG stars

• The gravitation is spherical potential

• The computational domain is a cube with equidistant directions, all the 6 surfaces have the same open boundaries

• Strictly LTE and short characteristic method

• Grey and non-grey (5 bins, under development)

Bolometric Intensity - Freytag et al. 2002

1111

QuickTime™ et undécompresseur codec YUV420

sont requis pour visionner cette image.

http://www.astro.uu.se/~bf/ (B. Freytag)

1212

Velocity fieldsVelocity fields Velocities are a Velocities are a

consequence of the strong consequence of the strong convective motions.convective motions.

Shock peak velocities Shock peak velocities saturates at saturates at 25 km/s. 25 km/s.

In the upper In the upper photosphere the photosphere the velocities are typically velocities are typically supersonic (supersonic (Mach>1Mach>1).).

Approx radius position

1

Radius (Rsun)

Ma

ch

nu

mb

er

1313

RSG simulations: state-of-the artRSG simulations: state-of-the art

CPU-time: 100 days more or less continuously CPU-time: 100 days more or less continuously on CPU-clock speed of 3 GHzon CPU-clock speed of 3 GHz

Drifting parameters, but relaxation in the last partDrifting parameters, but relaxation in the last part

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Polynomial fit

Rad

ius

(Rsu

n)

Time (years)

1414

Out lineOut line


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3D radiative transfer code 3D radiative transfer code OPTIM3D - 1OPTIM3D - 1

Integral computed Integral computed with Gauss-Laguerre with Gauss-Laguerre quadrature of order 9 quadrature of order 9



1.1 sec /

(numerical resolution 2353)

R = / = c/v 100000

at 6000 Å

~ 5 h / 1000Å ! (clock speed of 3 GHz)

1616


Opacity tables generated Opacity tables generated with MARCS with billion of with MARCS with billion of molecular (see Gustafsson, molecular (see Gustafsson, 2008) and atomic (VALD) 2008) and atomic (VALD) lineslines

Double linear interpolation Double linear interpolation for T and for T and only once only once

Linear interpolation at right Linear interpolation at right wavelengthwavelength

//= R = 500000= R = 500000

QuickTime™ e undecompressore TIFF (LZW)




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Cross-check: Linfor3D on 3D Cross-check: Linfor3D on 3D CO5BOLD local model for 3 CO5BOLD local model for 3 artificial iron linesartificial iron lines

Interpolation in the opacity tables Interpolation in the opacity tables is the main cause of the differenceis the main cause of the difference

OPTIM3D OPTIM3D large range of large range of wavelength + millions of lines wavelength + millions of lines simultaneouslysimultaneously

Linfor3D Linfor3D high performing high performing abundances determinationabundances determination





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OPTIM3D produces:OPTIM3D produces:UVES lpha Ori

RHD model

To constrain the To constrain the atmospheric atmospheric dynamics dynamics

To constrain the To constrain the structure sizestructure size



1919

Surface pattern of RSGsSurface pattern of RSGs

2020

QuickTime™ et undécompresseur H.264


H band - Large convective cellsH band - Large convective cells

Large cellLarge cell 400- 400-500 R500 Rsunsun, , lifetime lifetime of of yearsyears (st35gm03n07)(st35gm03n07)

Lifetime Lifetime intergranular intergranular lanes and dark lanes and dark spots spots few few monthsmonths



2121

Optical - complex convection Optical - complex convection patternpattern

Shocks+1000-1000 Rsun

H band TiO 6100 A Ca II H line

Complex substructures - More spectacular than in H band!Complex substructures - More spectacular than in H band! Inversion of the contrastInversion of the contrast Shocks in Ca II H line!Shocks in Ca II H line!

Young et al. 2000

Bright spot model for 700 nm (TiO)

mas

mas



Star at 174.3 pc

( 44.6 mas)

2222

PhotocenterPhotocenter

TiO displacement up to 120 RTiO displacement up to 120 Rsunsun (15% stellar radius) and 20 R (15% stellar radius) and 20 Rsunsun for H band for H band If alpha Ori at 200pc: - TiO displacement If alpha Ori at 200pc: - TiO displacement 2.8 mas 2.8 mas ((detectable detectable

with GAIA!with GAIA!)) - H band - H band 0.5 mas 0.5 mas

H band (3.5 years covered) TiO 6100 A (1.5 years covered)

+1 mas

-1 mas

-2 mas +1 mas



2323

SummarySummary

The convection pattern of RSGs The convection pattern of RSGs changes with the wavelengthchanges with the wavelength

Large convective cellsLarge convective cells Spectacular in the opticalSpectacular in the optical Calibration for GAIACalibration for GAIA

2424

Out lineOut line


2525

Characteristic velocities in the atmosphere - 1Characteristic velocities in the atmosphere - 1

How to extract dynamical information ?

Tomography (Alvarez et al. 2001)

Synthetic spectrum’s CCF in the optical range

Observed CCF of MuCep (Josselin & Plez, 2007)

asymmetric, variable cross-

correlation functions (CCF)

and irregular variations

Velocity (km/s)



Velocity (km/s)


sono necessari per visualizzare quest'immagine.C1QuickTime™ e un

decompressore TIFF (LZW)sono necessari per visualizzare quest'immagine.C8

2626










< v(C1) > = 2.3 km/s

simulation observations

The velocity amplitude is in qualitative agreement with the observations.

Even mask C1 is not 0 km/s

V466 Cas

2727




Representative Observations: time covered ≈ 1.5 year (Josselin & Plez

2007)

Simulation: time covered ≈ 1.5 year

The trend of the variations is in qualitative agreement (e.g., slope of the black curve)

Velocity amplitudes larger in the observations

v(C8r) vs v(C8b)v(C8r) vs C1v(C8b) vs C1

20 km/s

8 km/s

2828




Simulation: time covered ≈ 1.5 year

The trend of the variations is in qualitative agreement (e.g. slope blue and red)

C1 is deeper in the simulations

depth(C8r) vs v(C8b)

depth(C8r) vs C1

depth(C8b) vs C1

Representative Observations: time covered ≈ 1.5 year (Josselin & Plez

2007)

2929





CO lines comparison to Wallace & Hinkle, 1996 CO lines comparison to Wallace & Hinkle, 1996

=23057.543Å, =5.411 eV, log(gf)=-4.311

=23097.094Å, =1.476 eV, log(gf)=-4.195

< v correction > = - 2.3 km/s < v correction > = - 0.9 km/s

observations Colors 3.5 years covered

Depth and width reproduced without need for micro- or macro-turbulence.

Velocity (km/s)Velocity (km/s)

Flu

x (

arb

itra

ry u

nit

s)

Flu

x (

arb

itra

ry u

nit

s)



3030

CO lines comparison to Wallace & Hinkle, 1996CO lines comparison to Wallace & Hinkle, 1996



=23057.543Å, =5.411 eV, log(gf)=-4.311

=23097.094Å, =1.476 eV, log(gf)=-4.195

Velocity (km/s)

observations



Velocity (km/s)

Flu

x (

arb

itra

ry u

nit

s)

Flu

x (

arb

itra

ry u

nit

s)

Line asymmetries and shifts of few km/s.RHD simulation good for high but no good for lower

Colors 3.5 years covered

3131

Ti I line at 6261.11 Å - 1Ti I line at 6261.11 Å - 1

6262

Simulation - period covered 550 days with a time-step of 23 days

=6261.11Å, =3.430 eV, log(gf)=-5.735

Variations in the positions of the lines and their depths in Gray (2008), as already pointed out by Josselin & Plez 2007!!!!!!, and in RHD simulation

Variations in velocity!

a Ori (Gray, 2008)

FW

HM

(km

/s)

3232

Ti I line at 6261.11 Å - 2Ti I line at 6261.11 Å - 2 shapes at 1km/s level shifts much larger than

shape variations The predominant shape

is a reversed ”C”

Ori (Gray, 2008)

Time covered = 1.5 yQuickTime™ e un

decompressore TIFF (LZW)sono necessari per visualizzare quest'immagine.

Velocity (km/s)

3333

SummarySummary

RHD simulations are in RHD simulations are in qualitative qualitative agreement on the velocity amplitudeagreement on the velocity amplitude with with respect to the observationsrespect to the observations

No need for macro- turbulenceNo need for macro- turbulence Velocity correction due to the convectionVelocity correction due to the convection Bisector predominant shape is a reversed Bisector predominant shape is a reversed

”C” in accord with the observations”C” in accord with the observations

3434

Out lineOut line


3535

InterferometryInterferometryIONIC filter FLUOR filters

WaterCOCN

Global spectrum



3636



Intensity profiles and limb-darkening - 1Intensity profiles and limb-darkening - 1

Angular intensity dispersion is larger than the temporal ones

Angular



p/R

Temporal

Median

3737

Intensity profiles and limb-darkening - 2Intensity profiles and limb-darkening - 2

Claret LD law (2000) with new coefficients (blue)

Modification of LD law by Ludwig & Beckers (2008) (red)

Claret LD law withATLAS9 3500K,log(g)=0,

solar metallicity(green)


sono necessari per visualizzare quest'immagine.QuickTime™ e un


p/R cycles/R

RHD snapshot

3838

Numerical resolution and Numerical resolution and visibility mapsvisibility maps

Small bright artificial Small bright artificial patches (few pixels patches (few pixels wide)wide)

Median smoothing Median smoothing appliedapplied

Difference at 7th lobe Difference at 7th lobe (0.035 R(0.035 Rsunsun

-1-1, i.e. 28 , i.e. 28

RsunRsun3.3 pixel)3.3 pixel)

cycles/Rsun

No smoothingsmoothing

3939



Visibility - the first lobeVisibility - the first lobe



Angular synthetic vis H band LD UD of 16mas at 173 pc (70 Rsun)

Temporal fluctuationsAngular fluctuations

DispersionDispersion due to large (250-500 R due to large (250-500 Rsunsun) convective cells) convective cells Fluctuations are 10% at 0.006 RFluctuations are 10% at 0.006 Rsunsun

-1 -1 (first null point) (first null point) additional additional uncertainty for radius measurement!uncertainty for radius measurement!

No clear distinction between angular and temporal fluctuationsNo clear distinction between angular and temporal fluctuations

10% atfirst null

cycles/Rsun cycles/Rsun

€

Fluct =σ

vis

4040

Visibility - the second, third and fourth Visibility - the second, third and fourth lobeslobes

Clear Clear deviationdeviation from from circular symmetry. Signal circular symmetry. Signal higherhigher than UD or LD than UD or LD predictions!!!predictions!!!

Scatter becomes larger Scatter becomes larger with spatial frequencieswith spatial frequencies

Signature of the Signature of the characteristic sizecharacteristic size of of convective cellsconvective cells





120 Rsun (15% R)

70 Rsun (8% R)

50 Rsun (6% R)

cycles/Rsun

H band LD UD of 16 mas at 173 pc (70 Rsun)

4141



Visibility - the second, third and fourth Visibility - the second, third and fourth lobeslobes

Temporal fluctuationsAngular fluctuations

10%

Vis<10-14% Vis<6-10% Vis<2-7%

How to detectHow to detect this with today this with today interferometer:interferometer:

1.1. Searching for angular Searching for angular fluctuations using Earth fluctuations using Earth rotation (1 night, same rotation (1 night, same configuration)configuration)

2.2. Looking for temporal Looking for temporal fluctuations (1 night, same fluctuations (1 night, same configuration at two epochs)configuration at two epochs)

4242

Comparison to observations:Comparison to observations: Ori (Haubois et al. 2006) in IONIC Ori (Haubois et al. 2006) in IONIC

First data at high First data at high spatial frequencyspatial frequency

DataData from lower to from lower to higher frequency higher frequency explainedexplained with one with one model!model!

Characterization of Characterization of the convection size. the convection size. Ori covered by cells Ori covered by cells of 50-120 Rsunof 50-120 Rsun

More measure at 20-More measure at 20-25 arcsec25 arcsec-1-1 for for signature of large cellsignature of large cell



Spatial frequency

Sq

uar

ed V

isi b

ilit y

44.6 mas at 174.3 pc

UD of 43.65 mas

4343

Comparison to observations:Comparison to observations: Ori (Perrin et al. 2004) in K222 Ori (Perrin et al. 2004) in K222

Confirmation in Confirmation in the K band: the K band: presence of presence of cells cells of 50 to 120 Rof 50 to 120 Rsunsun

Measure at 20 to Measure at 20 to 23 arcsec23 arcsec-1-1 explainedexplained cells cells of of 200 R200 Rsunsun

UD of 43.65 mas







Vis

ibili

ty

Spatial frequency

43.6 mas at 179 pc

UD of 43.65 masLinear LD of 43.64 mas

4444

Importance of high spectral resolution - 1Importance of high spectral resolution - 1

Variation of the interferometric data between different spectral features, and between features and continuum

QuickTime™ et undécompresseur codec YUV420


Chiavassa et al., 2007 (SF2A)

4545

Importance of high spectral resolution - 2Importance of high spectral resolution - 2

The visibility is The visibility is wavelength wavelength dependent!dependent!

It is It is crucialcrucial to have to have high spectral high spectral resolutionresolution

H band is a good H band is a good target target

AMBER spectral resolution of 1500

Resolution of 12000

wavelength



45 mas at 173.5 pc

4646

Comparison to observations:Comparison to observations:Mu Cep (Perrin et al. 2005) in K band Mu Cep (Perrin et al. 2005) in K band

RHD model RHD model cannot fit all cannot fit all the data with the data with one model!one model!

Not even Not even changing changing cells cells distribution distribution

K203 K215

K222 K239









15.8 mas at 490 pc

<2%

Spatial frequency

4747

Closure phasesClosure phases

Commonly non zero Commonly non zero or ±or ± surface surface inhomogeneitiesinhomogeneities

Wavelength Wavelength dependentdependent

Necessary to observe Necessary to observe at at high spatial high spatial frequenciesfrequencies

H band has larger H band has larger dispersion dispersion

Max baseline (m)

Clo

sure

Ph

ase

(d

eg

ree)

IONIC

K222

Structures of50 Rsun

Structures of80 Rsun

4848

SummarySummary

Average limb-darkening profileAverage limb-darkening profile Convection-related surface structures cause Convection-related surface structures cause

visibility fluctuations that:visibility fluctuations that:1.1. Add uncertainty on radius measurementAdd uncertainty on radius measurement2.2. Clearly deviate from circular symmetry at high Clearly deviate from circular symmetry at high

frequencyfrequency Ori is covered by cells of 50-120 ROri is covered by cells of 50-120 Rsunsun Importance of high spectral resolution to Importance of high spectral resolution to

characterize the convection patterncharacterize the convection pattern

4949

Out lineOut line


5050

Conclusions - 1Conclusions - 1 The convection pattern in RSGs is wavelength The convection pattern in RSGs is wavelength

dependent. dependent. Few largeFew large (400-500 R (400-500 Rsunsun) convective ) convective cellscells in in the IR with a lifetime of years and complex pattern in the IR with a lifetime of years and complex pattern in the optical.the optical.

RHD simulations have been compared to observations:RHD simulations have been compared to observations:n Qualitative Qualitative agreementagreement on the velocity amplitude on the velocity amplituden No needNo need for macro-turbulence for macro-turbulencen Reverse-”C” shapeReverse-”C” shape, line shifts and asymmetries without , line shifts and asymmetries without

using or macro-turbulenceusing or macro-turbulencen DetectionDetection of convection cells on of convection cells on Ori from Ori from

interferometric datainterferometric data

5151

Conclusions and predictions - 2Conclusions and predictions - 2 The predictions of the The predictions of the photocenterphotocenter

displacementdisplacement are of extreme interest for are of extreme interest for future mission like GAIAfuture mission like GAIA

Today Today interferometersinterferometers are the are the best way to best way to detectdetect and characterize the convection on and characterize the convection on RSGs. The observation must go at higher RSGs. The observation must go at higher arcsecarcsec-1-1 beyond the determination of the beyond the determination of the radius and LD. Future resolved image will radius and LD. Future resolved image will constrain RHD simulationsconstrain RHD simulations

5252

Principal problem of RHD simulation is the grey Principal problem of RHD simulation is the grey treatment of opacities. Major efforts, both human treatment of opacities. Major efforts, both human and computer must be done.and computer must be done.

Possible effects of non-grey:Possible effects of non-grey:- for spectroscopy an increase of the contrast for spectroscopy an increase of the contrast

between weak and strong lines between weak and strong lines - for interferometry a reduction of the intensity for interferometry a reduction of the intensity

map contrast that implies smaller visibility map contrast that implies smaller visibility fluctuationsfluctuations

Conclusions - 3Conclusions - 3

5353

PerspectivesPerspectives SED (e.g. effective temperature scale to compare with SED (e.g. effective temperature scale to compare with

determinations with 1D models) determinations with 1D models) Opacity SamplingOpacity Sampling in in OPTIM3D using MARCS tablesOPTIM3D using MARCS tables

Switch to Switch to non-greynon-grey (coll. With B. Freytag and H.G. Ludwig) (coll. With B. Freytag and H.G. Ludwig) Inclusion of Inclusion of radiation pressureradiation pressure to study the winds (coll. to study the winds (coll.

with B. Freytag)with B. Freytag) More models of RSGs with different fundamental More models of RSGs with different fundamental

parameter neededparameter needed Natural extension of the work to Natural extension of the work to AGB and RGBAGB and RGB stars (e.g., stars (e.g.,

1D models by S. Höfner or 3D by B. Freytag and 3D local 1D models by S. Höfner or 3D by B. Freytag and 3D local models by H.G. Ludwig)models by H.G. Ludwig)

5454

Merci - GrazieMerci - Grazie!!!!!!



5656


The The relevant scalerelevant scale of convection is still uncertain of convection is still uncertain (large convective cells? Schwarzschild, 1975)(large convective cells? Schwarzschild, 1975)

The interpretation of the fundamental The interpretation of the fundamental parameters is based on a correct parameters is based on a correct characterizationcharacterization ofof RSG RSG convectionconvection

Strong Strong mass-lossmass-loss of unknown origin. Convection of unknown origin. Convection can explain?can explain?

The existence of The existence of MOLsphereMOLsphere around RSG is around RSG is sitll an open questionsitll an open question

5757

Velocity fieldsVelocity fields Velocities are a Velocities are a

consequence of the strong consequence of the strong convective motions.convective motions.

Radius (Rsun)

Radius (Rsun)

Ve

loc

ity

(km

/s)

+ 30

- 30

Shock peak velocities Shock peak velocities saturates at saturates at 25 km/s. 25 km/s.

In the upper In the upper photosphere the photosphere the velocities are typically velocities are typically supersonic (supersonic (Mach>1Mach>1).).

--- Approx radius position Sound speed

Approx radius position

Ma

ch

nu

mb

er

1

5858



Comparison to water vapor lines at 12 Comparison to water vapor lines at 12 m by m by Ryde et al. 2006Ryde et al. 2006

3D simulation1D MARCS at 3600K1D MARCS at 3200K

Observations

RHD simulation reproduce RHD simulation reproduce well Hwell H22O but there is no O but there is no

way to explain OH lines, way to explain OH lines, even changing the O even changing the O abundanceabundance

Shallow 3D temperature Shallow 3D temperature gradient. gradient.

Work still in progress, Work still in progress, testing MOLsphere testing MOLsphere modelsmodels



H2O

OH

MARCS 3200KMARCS 3600K

<3D>QuickTime™ e un


5959

Granulation contrastGranulation contrast

Under or over-estimated granulation size Under or over-estimated granulation size contrast in RHD models?contrast in RHD models?



In the intensity contrast is 50% smaller, the visibility fluctuations are also 50% (second and third lobe) and 40% (fourth lobe) smaller.

More difficult to detect!!!

Solid : top second lobeDotted : top third lobe

Dashed : top fourth lobe

6060

Comparison to observations:Comparison to observations:Mu Cep (Perrin et al. 2005) in K band - 2Mu Cep (Perrin et al. 2005) in K band - 2

MOLsphere extensionMOLsphere extension model with 7.91 mas, model with 7.91 mas, T=1700,T=1700,=10=10-12 -12 gr/cmgr/cm33

OK K203, unable to OK K203, unable to explain K239!explain K239!

Too high Too high or T or T opaque. opaque. Observational Observational check?check?

In progress, checking In progress, checking spectra Kband + 12 spectra Kband + 12 m m





Spatial frequency

K203 K239

6161

Importance of high spectral resolution - 2Importance of high spectral resolution - 2AMBER resolution of AMBER resolution of 3535

1.6 m-[0,310000] 2.22 m -[0,150000] 2.33 m -[0,90000]

H band contrast between dark and bright regions > K 2.22

Visibility is wavelength dependent

H band continuum is more interesting

But difficult to see difference from fluctuations at this resolution

cycles/Rsuncycles/Rsun

6262

Visibility in TiO Visibility in TiO bandsbands





atmospheric dynamics of red supergiant stars

Documents

key point

rsg starsthe gravitation

virtual observers

rsg questions

josselin et plez

co5bold conservative

strong convective motions

timevariable structure