A visible instrument for interferometry

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

Massive Stars: TopicsStellar surface studies: diameters, fast rotation, flattening, gravity darkening, differential rotationMultiplicity: Characterization of multiple systems, interactions between componentsCircumstellar environments: geometry and kinematics, mass flux determination, surface/disk interface 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 & Per, Lyr & Sgr, Sco, Cas, Aur, HD 200775)

1 paper on a diameter measurement (g Equ)1 paper on the geometry in the continuum(d Cep) 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 observationsVEGA 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 problemsscaling of spectraSaturation for bright objectsFilters loss of SNRV=3.5 (HR)B2V 200 pcD*= 0.25 masDenv = 2.5 - 5 masOther limitationsReduced SNR in the blue No phase closureVEGA on CHARANot very well optimised for the study of circumstellar environmentsMassive 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 =0.6)270m440m700mB (V=0.5 =0.6)660m1080m1730mB (V=0.9 =0.4)180m300m470mB (V=0.5 =0.4)440m720m1150mYES !!!

Solutions Longer baselinesShorter wavelengthsBetter precision

Massive Stars: Stellar SurfacesFast rotation: photosphere flattening

Measurements 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 V0.15mas)Massive Stars: Stellar SurfacesFast rotation: gravitational darkening

Spec. 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)

AltarMonnier et al. (2007)Measurements in the continuum or in linesSpectral resolution: NoResolving baselines(V ~ 0)Second visibility lobe Large BaselinesPhase closureImage Reconstruction + model-fitting

MASSIVE STARS: Stellar SurfacesFast rotation: differential rotation & gravitational darkening

In the continuumDegeneracy between et 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 15000 20km/s

Indirect measurement in emission lines

Stellar Spots

?

YesIf convective zone due to fast rotation

Detectable ?

Massive Stars: circumstellar environments

Visible Spectrum of the classical Be star Alpha AraeTowards the blue domainAtmospheric turbulenceAcces to faint linesPrecision