MASSIVE STARS b y Ph Stee Massive Stars subgroup Borges Fernandes Marcelo Carciofi Alex de Wit WillemJan Domiciano de Souza Armando Faes Daniel Kostogryz Nadia Meilland ID: 1034358
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1. A visible instrument for interferometryMASSIVE STARSby Ph. SteeMassive Stars sub-group:Borges Fernandes MarceloCarciofi Alexde Wit Willem-Jan Domiciano de Souza ArmandoFaes DanielKostogryz Nadia Meilland AnthonyMillour FlorentinNardetto Nicolas
2. Massive Stars: TopicsStellar surface studies: diameters, fast rotation, flattening, gravity darkening, differential rotation…Multiplicity: Characterization of multiple systems, interactions between components…Circumstellar environments: geometry and kinematics, mass flux determination, surface/disk interface…
3. Massive Stars: Scientific productionA very productive topic: 14 papers are about massive/hot stars for a total of 24 VEGA papers 10 papers on the geometry & kinematics of the circumstellar environment mainly in Ha: (AB Aur, Deneb & Rigel, 48 Per & ψ Per, β Lyr & υ Sgr, δ Sco, γ Cas, ε Aur, HD 200775)1 paper on a diameter measurement (g Equ)1 paper on the geometry in the continuum(d Cep)
4. Massive Stars: VEGA Targets In 2013: 10 programs on VEGA were about massive stars (50%)In 2014: 9 programs among 17 (1 on multiplicity (eclipsing binaries, e Aurigae, SS Lep), 4 on stellar surfaces (Bn, HD177724, HD209409, w Ori) , 4 on circumstellar environments (w Ori, 51 Oph, HD141569, Hypergiants)VEGA remote observations
5. VEGA actual limitationsMagnitude limitation (u,v) plane coverageMaximale Resolution D = 0.5 mas (B = 330 m)Limited for extended objects( > 2 mas)No compact triplet on CHARANot possible for D > 5.5 mas (B = 30 m)Detector problems« scaling » of spectraSaturation for bright objectsFilters loss of SNR V=3.5 (HR)B2V à 200 pcD*= 0.25 masDenv = 2.5 - 5 masOther limitationsReduced SNR in the blue No phase closure VEGA on CHARANot very well optimised for the study of circumstellar environments
6. Massive Stars: Stellar SurfacesDiameters measurements: - To constrain stellar evolution models of massive stars - To calibrate the surface-brightness relation (distance in the Universe)Spec. TLum. Cl.mV=5mV=6mV=7BIV-V2606831460III76185383I-II57165549OIV-V51318III458I-II41121Magnitude limitation ?NO !!!Spatial resolution problem ?For a B2VmV=5mV=6mV=7Distance400pc600pc1000pcDiameter0.13mas0.08mas0.05masB (V=0.9 λ=0.6)270m440m700mB (V=0.5 λ=0.6)660m1080m1730mB (V=0.9 λ=0.4)180m300m470mB (V=0.5 λ=0.4)440m720m1150mYES !!!Solutions Longer baselinesShorter wavelengthsBetter precision
7. Massive Stars: Stellar SurfacesFast rotation: photosphere flatteningMeasurements in the continuumSpectral resolution: NoNo resolving baselinesVisibility < 0.8 Maximum baselinesMultiple measurements Ex : Achernar flatteningDomiciano de Souza et al. (2003)Spec. Cl.Diam.Dist maxNb *B9 IV-V2.7 Ro150 pc131B5 IV-V3.9 Ro210 pc33B2 IV-V5.6 Ro300 pc51O9 IV-V7.9 Ro450 pc96Obs. with CHARA (B=330m pour V<0.8 D>0.15mas)
8. Massive Stars: Stellar SurfacesFast rotation: gravitational darkeningSpec. ClDiam.Dist maxNb *B9 IV-V2.7 Ro50 pc7B5 IV-V3.9 Ro70 pc2B2 IV-V5.6 Ro100 pc3O9 IV-V7.9 Ro150 pc1Obs. on CHARA (B=330m D>0.5mas)Alpha CepZhao et al. (2009)AltaïrMonnier et al. (2007)Measurements in the continuum or in linesSpectral resolution: NoResolving baselines(V ~ 0)Second visibility lobe Large BaselinesPhase closureImage Reconstruction + model-fitting
9. MASSIVE STARS: Stellar SurfacesFast rotation: differential rotation & gravitational darkeningIn the continuumDegeneracy between α et β In photospheric linesSpec. Cl.Diam.Dist maxNb *B9 IV-V2.7 Ro50 pc7B5 IV-V3.9 Ro70 pc2B2 IV-V5.6 Ro100 pc3O9 IV-V7.9 Ro150 pc1Obs on CHARA (B=330m D>0.5mas et mV<4)Multiple baselines per targetPrecision on the phase of ≈ degresRmin = 10000 (Ropt= 20000)Limited by the spatial resolution !Delaa et al. (2013)
10. Massive Stars: Stellar activity MagnetismDirect measurement ?Indirect measurement by the effect on the circumstellar environmentPulsationsImportance of NRP in the Be phenomenonMeasurement in photospheric linesS/N = 100R > 15000 20km/sIndirect measurement in emission linesStellar Spots?YesIf convective zone due to fast rotationDetectable ?
11. Massive Stars: circumstellar environmentsVisible Spectrum of the classical Be star Alpha AraeTowards the blue domainAtmospheric turbulenceAcces to faint linesPrecision <1% on diff. Vis.Out of the Ha line
12. Massive stars: image reconstructionNb de tel.3T4T5T6T7TTemps d’obs3n1.5n1n0.6n0.4nHD62623 : 3 nights with AMBERMillour et al. 2011Difficulities:phase closureSmall vivibilitiesIn the V band the CE of masive stars are generally:In the continuum:Flux dominated by the central starNeed high precision for the measurements (1%)In the emission lines:Continuum mostly unresolved « Auto-calibration »
13. Massive Stars: circumstellar environmentsMany objects: - Classical Be stars - Supergiants and unclassified B[e] - B & A supergiants - Yellow hypergiants - Wolf-Rayet - Novae
14. Massive stars: classical Be starsmV3456Nb of Stars112359102Magnitude is not a problem !Frémat et al. 2005Objectives :Kinematics within different spectral linesLink photosphere environmentBe-Shell i~90° disk opening anglePolar winds ?Statistical studiesVariability (Pulsation & Binarity)Modeling : ionization, Temperature, densityNeeds :Rmin = 1500 200 km/sRopt = 15000 20 km/sShort baselines (20-50m)High precision for the visibilities : 1-2% Faint visibilities (lines)Stee et al. 2012γ Cas
15. Massive stars: B[e]Objectives :Determine where the spectral lines are formedKinematics (disks vs winds)Objects classification (young/evolved/binaries)Variability (images as a function of time)Needs :Rmin = 1500 200 km/sRopt = 15000 20 km/sObjects mostly faint in VmV579Nb of stars1410But non exhaustive list of targetsHD62623Millour et al. 2011
16. Massive stars: Corotating-Interacting regionsOwocki, Cranmer and Fullerton, 1995Pole-on viewHarries et al. 1995Origin of these perturbations? Anchored magnetic fields Non-Radial pulsations+perturbation by fast rotationDessart & Chesneau 2002
17. Massive stars: B & A supergiantsChesneau et al. 2010Objectives :Diameters measurementsExtension in Hα (and other lines)Mass lossAsymmetry & time evolutionProblems : Over-resolved with CHARA/VEGASolutions :Concentrate on stars @ larger distancesSmaller baselines
18. Massive stars: Yellow hypergiantsObjectives:Constrain the geometry in the continuumStudy the instabilities in the atmosphere (spectral lines)Constrain the rotation (pseudo-photosphere)Companions detection and spectrum disentanglingNeeds : R = 30000 10km/smV = 5 (8)A least 2 targets identified (Nord hemisphere): ρ Cas HR 8752+ 2 objets with mV < 8+ 5 in the South hemisphereChesneau et al. (2014)D=3.6kc, UD=3.6mas!R*=1380 RsolHR5191
19. Massive stars: Wolf RayetWR 140mV=6.9Objectives :Extension in spectral linesProbing the ionization structureModeling the mass loss(Hillier & Dessart)Study the binarityNeeds :Large spectral lines R = 1500 200 km/sObjects faint in the visible (mV = 8)Numerous and very bright emission linesV=5.4
20. 46gain(2 mag)Amateur spectrumCont.V=7.9WR 137V=6.4Massive stars: Wolf Rayet
21. Massive stars: NovaeT Pyx observed withAMBERChesneau et al. 2011Bright targets during a short period of timeStrong lines in emissionRapid evolution of the circumstellar environmentStrong asymmetries developingReactivity + large number of baselines spectro-imagingSpectral resolution needed: at least 1500 200km/sIn 37 years 13 novae with mV<64 novae with mV<4mV=8 1 nova / per year for VEGAS1970 FH Serpentis 4 mag1975 V1500 Cygni 2.0 mag1975 V373 Scuti 6 mag1976 NQ Vulpeculae 6 mag1978 V1668 Cygni 6 mag1984 QU Vulpeculae 5.2 mag1986 V842 Centauri 4.6 mag1991 V838 Herculis 5.0 mag1992 V1974 Cygni 4.2 mag1999 V1494 Aquilae 5.0 mag1999 V382 Velorum 2.6 mag2006 RS Ophiuchi 4.5 mag2007 V1280 Scorpii 3.7 mag
22. Massive stars: multiplicity1 mas7-15 masHierarchical triple system ξ TauOrbits: 7 & 145 daysWhy ?Study of multiple systems provides accurate massesConstraints on the formation of massive stars ?How ?Need long and short baselines simultaneously => Image is a must have !“Super-synthesis” effect thanks to spectral resolutionMany targets up to V = 7
23. Massive stars: interactionX-Ray Be-binaries : Prototype β LyrD = 1 masT = 12.9 jours- Perfectly suited for imaging with 300m baselines- First convincing studies in the lines with VEGA - First image with MIRCImages in Continuum + Lines (Hα, Hβ & HeI)Companion deformationSpatial geometry of the ionized gazGas kinematicsPhysical conditions for the CE (T,ρ, ni)Constraints on the mass lossOther similar objects possibleImages MIRC de β Lyr Zhao et al. 2008
24. Massive stars: global specificationsSpectral modes : 2, 3 ou 4HR1 : R=30000-40000 7-10 km/s Pulsations, rotation, supergiants rotationHR2 : R=10000-15000 20-30 km/s Fast Rotation, disks & windsMR : R=2000-5000 60-150 km/s Wolf-Rayet, spectro faint CE LR : R<500 X Stellar diameters, reddened sourcesSensibility :mV = 5 for HR1mV = 7 for HR2mV = 9 for MRmV = ? LRMeasurements accuracy:Faint visibilities (stellar surfaces)v = few % in the continuum (Cont. Env.)v= few 0.1% in lines (Pulsations) = 1° in lines (Rotation/Pulsation)Phase closure constraintsNumber of telescopes: At least 5 telescopes for 1 image/nightShort baselines mandatory (20-30m) and large (>300m) depending on the science objectives.
25. Where ?Many large baselines (330m)Flexible organization2 “small” baselines (34m & 66m)Fixe telescopesOnly small telescopesMany short baselines (10-50m)Large telescopes 8.2m (UT)AT 1.6m = 1 more mag compared to CHARAMaximum number of 4 telescopesNo large baselines ( > 200 m )ESO organization ;-) Stellar surfaces vs Circumstellar environmentsCHARAVLTI
26. MROI ?9 movable telescopes (1.4 m)28 stationsBaselines from 8 to 340 mLarge or compact configurations possible