Science with the Very Large Telescope Interferometer (VLT-I) Jean-Baptiste Le Bouquin (ESO, Chile)...

Science with the Very Large Telescope Interferometer (VLT-I)

Jean-Baptiste Le Bouquin (ESO, Chile)for

VLTI Team, AMBER team, MIDI team, PRIMA team…

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The VLTI at Cerro Paranal (II region)

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Betelgeuse ~ largest star on the sky(model by Freytag et al.)

The diffraction limit:Spatial resolution versus telescope size

1.5 mas = VLTI

40 mas = 8m telescope with perfect AO(best NACO performances)

0.5as = 8m telescope(FORS with seeing of 0.5”)

8 mas = 40m ELTwith perfect AO

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The evolved star Mira imaged by HST in the UV.

And not only Betelgeuse has interesting features

Indirect reconstruction of AB Dor

(magnetic spots) Long term goal: image other stars as we image the Sun !

Betelgeuse(model of convection)A normal star with its 5

branches

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Beyond the diffraction limit…The power of interferometric fringes

Objects Single Telescope of 8m2 Telescopes of 8m separated by 50m

Small !

Big !

Any differences ?

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Practice: What is this object ?

8m TelescopeObject: a close binary

(here as seen with a single telescope of 50m)

2 Telescopes of 8m separated by

50m…

… and with different

baseline angles

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The Very Large Telescope InterferometerQuickTime™ et undécompresseur

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The Very Large Telescope Interferometer

• Emulate a 180m telescope at cerro Paranal, by optical Interferometry

• 4 UTs : 8m, fixed telescopes(~few night per month)

• 4 ATs : 1.8m movable telescopes(every night)

• Instruments: AMBER MIDI PRIMA Future instruments

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4 movable ATs

4 fixed UTs

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The Very Large Telescope Interferometer



Overview of Cerro Paranal

Full power:~200x120m telescope

Current VLTI:~120x80m telescope

Limiting magnitude

Spatial resolution

E-ELT40m telescope

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Current Instrumentation

• AMBER 3 telescopes J, H and K bands (near-IR) spectrograph

R=45, 1.200, 10.000

FOV: 150mas Spatial resolution: 2mas Limiting magnitude: K~8mag

• MIDI 2 telescopes N band (mid-IR) spectrograph

FOV: ~2arcsec Spatial resolution: 15mas Limiting magnitude: ~5Jy


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Science with VLTI• VINCI commissioning instrument (~40 referee papers)

First radius measurements of very low mass stars with the VLTI Direct diameter measurement of a star filling its Roche lobe Gravitational-darkening of Altair from interferometry Cepheid distances from infrared long-baseline interferometry …

• MIDI instrument (~40 referee papers) Monitoring of the dust formation event of the Nova V1280 Sco Extended envelopes around Galactic Cepheids Probing the dusty environment of the nucleus in NGC 3783 The post-AGB binary IRAS 08544-4431: circumbinary disc resolved …

• AMBER instrument (~20 referee papers) Spatially resolving the hot CO around the young Be star 51 Oph A young high-mass star rotating at critical velocity Diameter and photospheric structures of Canopus …

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Science with VLTI : examplesQuickTime™ et undécompresseur


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Stellar parameters and stellar activity

Diameter of V3879 Sgr (M4III)

• This star is pulsating: perfectly radial pulsations ? follow the pulsation

• This star is convective: why we don’t see any

asymmetries ? upper limits on the convective

cell contrast : ~1%

diam = 7.52mas +/- 0.2%,and perfectly circular

BUT

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Density waves in circum-stellar disks

Model of Be star:photosphere + rotating disk

AMBER astrometryacross a line formed in the disk

• Disk has a right/left asymmetry = density wave• Is it counter-rotating ?

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Resolving the photosphere of fast rotators

HST imagesAMBER astrometry

Fomalhaut

• Disk and star are aligned, like in the solar system• Does the star and the planet rotate the same way ?

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Evolved stars : shell around Mira stars

H-band (water) H-band K-band (CO)

• How these stars (T=3500K) can create molecules ?

• How is this material dispersed in the Interstellar Medium ?

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Incoming: precise astrometry with PRIMA

• Product and strategy: precise astrometry between the 2

stars (10micro-as) long term follow-up (several

years)

• Goals: real mass of known planets

(unveiling V from Vsini) new detections stellar activity (spots, convection) off-axis fringe-tracking for AMBER

and MIDI …



• Concept: dual-beam (2 stars) 2 telescopes

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Toward full power…

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Future Instrumentation : GRAVITY

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• Relativistic orbits of stars close to the horizon of Sgr A*

• Hot spots in the last stable orbit

Current observations of stars around Sgr A*

• Put into test the strong field limit of General Relativity (untested so far)

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Future instrumentation : GRAVITY

• Combining 4 UTs imaging capability

• AO with IR wavefront-sensor no bright visible source around Sgr A*

• Off-axis fringe-tracking K~10 for the bright on-axis one K~15 for the faint, off-axis one

• Detecting the hot spots on the last stable orbit: 5 micro-as precision at K~15 in few minutes

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Future instrumentation : general purpose imaging instruments (MATIS, VSI…)

• Goal: provide the community with images at few mas spatial resolution, in the J,H, K and N-band, in one night of observation, down to a magnitude K~11

20mas

• Science goals: Formation of stars and planets Imaging stellar surfaces Evolved stars, stellar remnants

& stellar winds Active Galactic Nuclei & Super

massive Black Holes

An evolved star imaged by current VLTI

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VLT-I: a complementary facility in the ALMA and E-ELT area

Science with the Very Large Telescope Interferometer (VLT-I) Jean-Baptiste Le Bouquin (ESO, Chile)...

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