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Science with the Very Large Telescope Interferometer (VLT-I) Jean-Baptiste Le Bouquin (ESO, Chile) for VLTI Team, AMBER team, MIDI team, PRIMA team… QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. The VLTI at Cerro Paranal (II region) The diffraction limit: Spatial resolution versus telescope size 0.5as = 8m telescope (FORS with seeing of 0.5”) Betelgeuse ~ largest star on the sky (model by Freytag et al.) 40 mas = 8m telescope with perfect AO (best NACO performances) 8 mas = 40m ELT with perfect AO 1.5 mas = VLTI 2 And not only Betelgeuse has interesting features Betelgeuse (model of convection) A normal star with its 5 branches The evolved star Mira imaged by HST in the UV. Indirect reconstruction of AB Dor (magnetic spots) Long term goal: image other stars as we image the Sun ! 3 Beyond the diffraction limit… The power of interferometric fringes Small ! Any differences ? Big ! Objects Single Telescope of 8m 2 Telescopes of 8m separated by 50m 4 Practice: What is this object ? Object: a close binary 8m Telescope (here as seen with a single telescope of 50m) 2 Telescopes of 8m separated by 50m… … and with different baseline angles 5 The Very Large Telescope Interferometer QuickTime™ et un décompresseur sont requis pour visionner cette image. 6 The Very Large Telescope Interferometer • Emulate a 180m telescope at cerro Paranal, by optical Interferometry 4 fixed UTs • 4 UTs : 8m, fixed telescopes (~few night per month) QuickTime™ et un décompresseur sont requis pour visionner cette image. • 4 ATs : 1.8m movable telescopes (every night) • Instruments: AMBER MIDI PRIMA Future instruments 4 movable ATs QuickTime™ et un décompresseur sont requis pour visionner cette image. 7 The Very Large Telescope Interferometer Overview of Cerro Paranal Limiting magnitude Spatial resolution Full power: ~200x120m telescope QuickTime™ et un décompresseur sont requis pour visionner cette image. Current VLTI: ~120x80m telescope E-ELT 40m telescope 8 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 QuickTime™ et un décompresseur sont requis pour visionner cette image. • MIDI 2 telescopes N band (mid-IR) spectrograph FOV: ~2arcsec Spatial resolution: 15mas Limiting magnitude: ~5Jy QuickTime™ et un décompresseur sont requis pour visionner cette image. 9 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 … 10 Science with VLTI : examples QuickTime™ et un décompresseur sont requis pour visionner cette image. 11 Stellar parameters and stellar activity Diameter of V3879 Sgr (M4III) diam = 7.52mas +/- 0.2%, and perfectly circular BUT • 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% 12 Density waves in circum-stellar disks Model of Be star: photosphere + rotating disk AMBER astrometry across a line formed in the disk • Disk has a right/left asymmetry = density wave • Is it counter-rotating ? 13 Resolving the photosphere of fast rotators AMBER astrometry HST images Fomalhaut • Disk and star are aligned, like in the solar system • Does the star and the planet rotate the same way ? 14 Evolved stars : shell around Mira stars • How these stars (T=3500K) can create molecules ? • How is this material dispersed in the Interstellar Medium ? H-band (water) H-band K-band (CO) 15 Incoming: precise astrometry with PRIMA • Concept: dual-beam (2 stars) 2 telescopes • Product and strategy: precise astrometry between the 2 stars (10micro-as) long term follow-up (several years) • Goals: QuickTime™ et un décompresseur sont requis pour visionner cette image. real mass of known planets (unveiling V from Vsini) new detections stellar activity (spots, convection) off-axis fringe-tracking for AMBER and MIDI … 16 Toward full power… QuickTime™ et un décompresseur sont requis pour visionner cette image. 17 Future Instrumentation : GRAVITY Current observations of stars around Sgr A* • Relativistic orbits of stars close to the horizon of Sgr A* • Hot spots in the last stable orbit QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. • Put into test the strong field limit of General Relativity (untested so far) 18 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 19 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 • 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 20mas 20 VLT-I: a complementary facility in the ALMA and E-ELT area QuickTime™ et un décompresseur sont requis pour visionner cette image. 21