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

Science with the Very Large Telescope Interferometer (VLT-I). Jean-Baptiste Le Bouquin (ESO, Chile) for VLTI Team, AMBER team, MIDI team, PRIMA team…. The VLTI at Cerro Paranal (II region). The diffraction limit: Spatial resolution versus telescope size.

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

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  1. Science with the Very Large Telescope Interferometer (VLT-I) Jean-Baptiste Le Bouquin (ESO, Chile) for VLTI Team, AMBER team, MIDI team, PRIMA team… The VLTI at Cerro Paranal (II region)

  2. The diffraction limit:Spatial resolution versus telescope size Betelgeuse ~ largest star on the sky(model by Freytag et al.) 0.5as = 8m telescope (FORS with seeing of 0.5”) 40 mas = 8m telescope with perfect AO (best NACO performances) 8 mas = 40m ELTwith perfect AO 1.5 mas = VLTI

  3. And not only Betelgeuse has interesting features The evolved star Mira imaged by HST in the UV. Betelgeuse(model of convection) A normal star with its 5 branches Indirect reconstruction of AB Dor(magnetic spots) Long term goal: image other stars as we image the Sun !

  4. Beyond the diffraction limit…The power of interferometric fringes Small ! Big ! Any differences ? 2 Telescopes of 8m separated by 50m Objects Single Telescope of 8m

  5. Practice: What is this object ? Object: a close binary (here as seen with a single telescope of 50m) 2 Telescopes of 8m separated by 50m… … and with differentbaseline angles 8m Telescope

  6. The Very Large Telescope Interferometer

  7. 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 The Very Large Telescope Interferometer 4 fixed UTs 4 movable ATs

  8. The Very Large Telescope Interferometer Full power: ~200x120m telescope Current VLTI: ~120x80m telescope E-ELT40m telescope Overview of Cerro Paranal Limiting magnitude Spatial resolution

  9. 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 Current Instrumentation

  10. 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 … Science with VLTI

  11. Science with VLTI : examples

  12. Stellar parameters and stellar activity • 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 Diameter of V3879 Sgr (M4III) BUT

  13. Density waves in circum-stellar disks • Disk has a right/left asymmetry = density wave • Is it counter-rotating ? Model of Be star:photosphere + rotating disk AMBER astrometryacross a line formed in the disk

  14. Resolving the photosphere of fast rotators • Disk and star are aligned, like in the solar system • Does the star and the planet rotate the same way ? HST images AMBER astrometry Fomalhaut

  15. 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)

  16. 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 … Incoming: precise astrometry with PRIMA • Concept: • dual-beam (2 stars) • 2 telescopes

  17. Toward full power…

  18. Relativistic orbits of stars close to the horizon of Sgr A* Future Instrumentation : GRAVITY Current observations of stars around Sgr A* • Hot spots in the last stable orbit • Put into test the strong field limit of General Relativity (untested so far)

  19. 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 Future instrumentation : GRAVITY

  20. 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 Future instrumentation : general purpose imaging instruments (MATIS, VSI…) An evolved star imaged by current VLTI • Science goals: • Formation of stars and planets • Imaging stellar surfaces • Evolved stars, stellar remnants & stellar winds • Active Galactic Nuclei & Super massive Black Holes 20mas

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

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