AMBER observations of AMBER observations of Be StarsBe Stars

Anthony MeillandAnd Philippe Stee

Be Stars definitionBe Stars definition

Active hot Stars :

8000K<Teff<40000k

Emission lines

Infrared Exces

Non Supergiant stars

Near main sequence

exclude Herbig Ae/Be (Young stars)

exclude P Cygny (Supergiant stars)

No Forbidden lines

exclude B[e] stars

Include Be-shell (edge-on Be stars )

Be one day Be forever

Questions about Be starsQuestions about Be stars

Ejection of Matter from the central star

Rapid Rotation

Radiative stellar wind

Non-radial pulsations

Magnetism

Reorganization of the matter around the star

Expanding or rotating disk

Polar wind strength

Effect of magnetic fields

Disk open angle (Hydrostatic equilibrium, wind compressed disk)

Variability : origin and role

Pulsations

Equatorial disk formation and dissipation (Be Be-Shell B normal)

Continuous mass ejection or outbursts

Overdensity rotation or precession (One-Armed Oscillation)

Magnetic fields effect

Why using differential interferometryWhy using differential interferometryTo study Be stars?To study Be stars?

Rot

Exp

Results and futures observationsResults and futures observations

α Arae (MIDI + AMBER)α Arae (MIDI + AMBER)

Achernar (VINCI)Achernar (VINCI)

Κ CMA (AMBER)Κ CMA (AMBER)

Coming soon!Coming soon!New AMBER + MIDINew AMBER + MIDI

Coming not so soon Coming not so soon But we hope not too late!But we hope not too late!

New AMBERNew AMBER

δ Sco δ Sco AMBERAMBER

B=79 m , PA = 55°B=79 m , PA = 55°

8-13.5μm Visibilities8-13.5μm Visibilities

B=102 m , PA = 7°B=102 m , PA = 7°

αα Ara Observed with MIDIAra Observed with MIDI

unresolvedSmaller than what we expected

(<3mas for UD or <7mas US+UD)

Chesneau, Meilland et. Al A&A 2005

Companion at 32R*?

Short term Spectroscopic variationsShort term Spectroscopic variations

Disk truncation at 22R* ?

αα Ara Observed with AMBERAra Observed with AMBER

Meilland et al. 2007 A&A

Enveloppe ~40% total flux at 2μm

No significant envelope size variation

Between 2 and 13μm

Envelope extensionEnvelope extension

αα Ara Observed with AMBERAra Observed with AMBERgeometrygeometry

Meilland et al. 2007 A&A

αα Ara Observed with AMBERAra Observed with AMBERgeometrygeometry

Meilland et al. 2007 A&A

αα Ara Observed with AMBERAra Observed with AMBERgeometrygeometry

Meilland et al. 2007 A&A

αα Ara Observed with AMBERAra Observed with AMBERgeometrygeometry

Meilland et al. 2007 A&A

VΦ >> Vr VΦ ~ Vr

αα Ara Observed with AMBERAra Observed with AMBERKinematics : expansion or rotation (or both)Kinematics : expansion or rotation (or both)

Meilland et al. 2007 A&A

VΦ >> Vr VΦ ~ Vr

αα Ara Observed with AMBERAra Observed with AMBERKinematics : expansion or rotation (or both)Kinematics : expansion or rotation (or both)

Meilland et al. 2007 A&A

Keplerian rotation (β =0.48±0.05)

Critical rotation Vrot~Vc

αα Ara Observed with AMBERAra Observed with AMBERKinematics : expansion or rotation (or both)Kinematics : expansion or rotation (or both)

Meilland et al. 2007 A&A

Best Simeca modelBest Simeca model

ρequ

ρpol

~10-100

Vexp(eq)<10kms-1

Vexp(pol)~100-1000kms-1

Φequ

Φpol

<10

Rdisk =32R*

αα Ara Observed with AMBERAra Observed with AMBER

Meilland et al. 2007 A&A

Disk and Wind Disk and Wind

Achernar (VINCI)Achernar (VINCI)

5% total flux

No equatorial disk (<5R*)

Kervella et Domiciano de Souza. 2006 A&A

ΚΚ CMA (AMBER) CMA (AMBER)

No polar wind detected

Poorly resolved

Meilland et al. 2007 A&A

Equatorial disk : 50% of ftot at 2μm

Rdisk = 23R*

Disk and wind Disk and wind

Polar wind ( α Arae and Achernar)

Ljet>10R*

Fjet~1-5%F*

different mechanisms produce thepolar wind and the Equatorial disk ?

Disk open angle?

Wind open angle?

And Between?

Permanent Equatorial disk ( α Arae and κ Cma )

Rdisk~20-30 R*

Fdisk(K)~0.5Ftot

(also spectroscopic clues of a non permanent disk around Achernar 8R*)

KINEMATICSKINEMATICS

κκ CMaCMa

Non keplerian rotation (β =0.3±0.1)

Sub-critical rotation Vrot~0.52Vc

NO expansion (VΦ >> Vr )

Inhomogeneity aligned with major-axe?

Meilland et al. 2007 A&A

AchernarAchernar

Critical rotation

No equatorial disk during VINCI obervations In 2002

Disk between 1991 and 1998?

Domiciano de Souza et al. A&A

Vinicius et al. 2005 A&A

NEXT?NEXT?

Image reconstruction with AMBERImage reconstruction with AMBER4 Complete observation nights avec each of the 4 «triplets» available for P794 Complete observation nights avec each of the 4 «triplets» available for P79

PSF (72 bases ATs)

α Arae Achernar

Accepted Rejected

Formation et Dissipation des DisquesFormation et Dissipation des Disques

Vinicius, Zorec et al. (2005)

Double peak separation variations (DPS)

DPSmax=460kms-1~2.vsin i

DPSmin=160kms-1

Equilavent Width variations (EW)

Achernar

vr = 0.2 km.s-1

r (R*)

ρ(r)

vx/vsini

I

Outburst

Formation et Dissipation des DisquesFormation et Dissipation des DisquesAchernar

Disk and Wind « independant »

Outburst from 1991 to1995

Nouvel Outburst Depuis 2002?

3ème Phase?

Vr~0.2kms-1

Rmax~8R* (if keplerian)

Wind > 10R*

Critical rotation

AMBER LR (Imagerie) + AMBER HR (cinématique)

Meilland et al. En preparation

Disk creation and dissipationDisk creation and dissipationδ Sco

Miroshnichenko et al. 2003 A&A 408,305

Start in 2000 (Periastron)

Rdisk(2003)~10R*

Vr~0.4kms-1

Keplerian?

Multiples outburst?

Formation et Dissipation des DisquesFormation et Dissipation des Disquesδ Sco

Flux constant

Outburst

ConclusionConclusion