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Recent science results from VLTI commissioning

Recent science results from VLTI commissioning. Francesco Paresce European Southern Observatory. P70 VINCI Shared Risk Proposals. Time allocated: 150 hrs (~15 nights) on SIDS Proposals received: 40 for a total of > 600 hrs

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Recent science results from VLTI commissioning

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  1. Recent science results from VLTI commissioning Francesco Paresce European Southern Observatory Ringberg Workshop

  2. P70VINCIShared Risk Proposals • Time allocated: 150 hrs (~15 nights) on SIDS • Proposals received: 40 for a total of > 600 hrs • Ad-hoc scientific review committee: F.Paresce, C.Leinert, J.Surdej, P.Lena • Technical feasibility review: M.Schoeller, P.Kervella, M.Wittkowski • 16 Proposals accepted for 150 hrs Ringberg Workshop

  3. Cepheid Angular Diameters, PI: Kervella, ESO • Hot rapid rotators, PI: Domiciano, Nice • Dusty environment of RAqr, PI: Driebe, Bonn • Circumstellar matter around SS Lep, PI: Lachaume, Grenoble • VLTI Calibrators, PI: Percheron, Leiden • Central Source in Eta Car, PI: Schoeller, ESO • Radius of K&M dwarfs, PI: Segransan, Geneve • Simultaneous VLTI/VLBA measurements of Mira stars, PI: Wittkowski, ESO Ringberg Workshop

  4. Observations of HR 4049, PI: Dominik, Amsterdam • Rotation axis of V Hydra, PI: Haniff, Cambridge • Asteroseismology of roApstars, PI: Cunha, CAUP, Portugal • Radii of Asteroseismic target stars, Texeira, CAUP & IFA • Resolve Orbit of Theta 1c Ori, PI: Preibisch, Bonn • Observations of Rotationally Distorted Stars, PI: Van Belle, JPL • Short Period Binaries in Hierarchical triples, PI: Queloz, Geneve • Mass of the nearest WR star, PI: Buscher, Cambridge Ringberg Workshop

  5. P71 VINCI Shared Risk Proposals • Time allocated: 150 hrs (~15 nights) on SIDS • 26 proposals received for ~ 500 hours • Proposals reviewed by OPC • 16 proposals accepted in Category B for 270 hours • Technical feasibility review indicates that 13 proposals are feasible for a total of 230 hours Ringberg Workshop

  6. Inner disk structure in HAeBe systems, PI:Testi • Direct limb-darkening measurements of cool giant stars as tests of stellar model atmospheres, PI: Wittkowski • Direct interferometric measurement of the angular diameters of southern Cepheids, PI: Kervella • VINCI measurement of binaries using coherent techniques in preparation for extra-solar planet detection, PI: Meisner • Unveiling Eta Car’s dust environment, PI: Weis • Construction of a semi-empirical M-R relationship for MS stars from B to K, PI: Kervella • Probing and monitoring the core of Eta Car with mas resolution, PI: Schoeller Ringberg Workshop

  7. First Papers • First radius measurements of very low mass stars with the VLTI, Segransan et al., 2003, A&A, 397, L5 ESO Press Release 22/02,29 November 2002. How Small are Small Stars Really? VLT Interferometer Measures the Size of Proxima Centauri and Other Nearby Stars • The diameters of Alpha Centauri A and B: a comparison of the asteroseismic and VLTI views, Kervella et al., 2003, A&A, 404, 1087 ESO Press Release 05/03,15 March 2003. A Family Portrait of the Alpha Centauri System: VLT Interferometer Studies the Nearest Stars • The spinning-top Be star Achernar from VLTI-VINCI, Domiciano de Souza et al., 2003, A&A, in press ESO Press Release 14/03. Flattest Star Ever Seen, VLT Interferometer Measurements of Achernar Challenge Stellar Theory • Calibration observations of Fomalhaut with the VLTI, Davis et al., 2003, A&A, submitted Ringberg Workshop

  8. First Papers (cont.) • The interferometric diameter and internal structure of Sirius A, Kervella et al., 2003, A&A submitted • Direct measurement of the size of the star Eta Carinae, Van Boekel et al., 2003, ApJ, submitted • Tests of stellar model atmospheres by optical interferometry: VLTI/VINCI limb-darkening measurements of the M4 giant ψ Phe, Wittkowski et al., 2003, A&A, submitted • Introduction to VINCI/VLTI interferometric data analysis, Kervella et al., 2003, A&A, submitted • The diameter and evolutionary state of ProcyonA: multi-technique modeling using asteroseismic and interferometric constraints, Kervella et al., 2003, A&A, submitted Ringberg Workshop

  9. Ringberg Workshop

  10. Eta Carinae: some basic facts • In Tr 16 in Carina nebula (NGC 3372,) located at 2.5 +/- 0.3 kpc {MHII ~ 104 M ~ 103 x Orion} • Super massive LBV: ~ 100 M • Super luminous: 3-5x106 L (most lum. in MW) now but ~30 x 106 L at outburst (2nd brightest object in sky) • Super hot: 15-40 x 103 K • Super active: survivor of 1843 eruption that created the homunculus and expelled ~ 2-3M at up to 800 km/s • Current rate of mass loss 0.3-3 x 10-3 M/yr • Central object is not viewed directly but is obscured by several mag of extinction in near IR Ringberg Workshop

  11. Ringberg Workshop

  12. Eta Carinae: Questions & Mysteries • What was it? Yellow SG? Red SG?, WR? • What is it? Single? Binary? Cluster? What is its current mass loss rate exactly? What is its or their mass? • What will it become? Normal star after more eruptions? Collapse into SN or hypernova? • Is it rotating? What is the origin of the 5.5yr periodicity in some lines and x-rays? Is there a massive equatorial torus? • What is the physical mechanism responsible for the violent instability (outburst(s)), the homunculus bipolar geometry, the double ring structure seen in the mid IR in the inner homunculus and the x-ray emission? • What is going to happen this summer at x-ray peak? Ringberg Workshop

  13. Ringberg Workshop

  14. Ringberg Workshop

  15. Eta Carinae: why is it important? • Formation and evolution of extremely massive stars (most likely the first stars were this big): accretion onto a single object or mergers? • Dynamical and chemical interactions with their environment • The role of stellar instabilities in the outer envelopes of single stars and/or of periodic tidal forcing by a companion and the formation of asymmetric nebulosity • The relation of extremely massive stars to peculiar supernovae and hypernovae. Ringberg Workshop

  16. The key to understanding Eta Car is to penetrate into the core and “see” the central “object”. This is the main objective of the VLT/VLTI observations. Ringberg Workshop

  17. Very High Resolution VLT Imaging (70mas) • NACO on Yepun at 2.39μ • A unresolved at 70 mas • 57% of total flux seen in image (1.7” squared) concentrated in A corresponding to ~180Jy • Blobs D,C already detected by speckle interferometry Ringberg Workshop

  18. Very, very high resolution interferometry with VLTI (1mas) • Size of source = 5mas • Responsible for 180 Jy emission from an area of ~10 AU2 at 2.4 kpc • For 2 mags of extinction, Tmin ~ 4800 K • Dust evaporates at T>1500K so flux not due to thermal emission from dust • Conclusion: star and ionized wind spatially resolved (for first time)! Ringberg Workshop

  19. Analysis & Results Wind model assumptions: • Spherical star with dense, ionized and isothermal stellar wind • Gas accelerates from initial v0 to terminal velocity v∞ as v(r) = v0+(1-R*/r)(v∞-v0) • Wind is clumpy: f = <ρ>/ ρ • Main sources of opacity: f-f and f-b absorption and Thomson scattering Using HST/STIS long slit spectra that give: Mdot/√f = 3.16 10-3 M/yr (dashed line) Results: • Mdot = 1.5+/- 0.3 M/yr, f = 0.2 • No other component is contributing on spatial scales between 5 and 70 mas at K (a companion, material in orbital plane, dust in line of sight etc) Ringberg Workshop

  20. But, it’s not round! • Clear variation of visibility with projected baseline orientation • Assuming gaussian shape of wind: major axis = 8mas, minor axis = 6mas with PA=31+/-10 º • This PA is remarquably close to 45 º PA of major axis of homunculus! • Rapid rotation will cause enhanced mass flux from poles • Our observations mean that the homunculus is roughly aligned with the rotation axis of the star. Ringberg Workshop

  21. Observed de-projected aspect ratio = 1.6 • For rotation to flatten the star to this level, radiation driven wind models require rotation at 0.8-0.9 of break-up velocity! • At such speeds, Mdot will be ~ 8x the non rotating case • Wind asymmetries assumed to explain long slit HST results (see figure above) are consistent with this scenario. Ringberg Workshop

  22. Another very distorted star: Achernar • Aerial view of VLTI ground baselines for the two pairs of siderostats used for Achernar observations. Color magenta represents the 66m counted from North to East) and green the 140m. • Corresponding baseline projections onto the sky (Bproj) as seen from the star. Note the very efficient supersynthesis (different projections due to Earth rotation) resulting in a nearly complete coverage in azimuth angles. Ringberg Workshop

  23. Observations • Fit of an ellipse over the observed V2 points translated to equivalent uniform disc angular diameters. Magenta points are for the 66m baseline and green points are for the 140m baseline. The fitted ellipse results in major axis 2a=2.53±0.06 mas, minor axis 2b=1.62±0.01 mas, and minor-axis orientation PA=39±1° (from North to East). The points distribution reveals an extremely oblate shape with an aspect ratio 2a/2b = 1.56±0.05. Ringberg Workshop

  24. Analysis and Results B3Vpe star models used include: • Radiation transfer • Gravity darkening (von Zeipel) • Geometrical distortion due to solid body rotation and mass concentrated at the star center • Stellar parameters from lit (225km/s projected velocity etc) An extreme uniform Roche model with veq=vcrit and i=90° was also used Results: • Be star models don’t work • Extreme (equator-on, rotation at break-up speed) Roche model does but…it is not consistent with known properties of Be stars (not uniform or rotating at critical speed) But…maybe we don’t understand Be stars! Ringberg Workshop

  25. Science Demonstration Time in P71 3 nights with MIDI and the UTs without AO carried out in the June 11-16, 2003 period with UT1+3. Program approved by IC Program summary: 1. MIDI Observations of the heart of AGN: probing the dusty torus Rottgering, Leiden (PI), NGC 1068 2. Probing the disk of Be and B[e] stars with MIDI. Herbst, Heidelberg (PI), HD 316285 3. A study of disk structure around Herbig AeBe stars Waters, Amsterdam (PI), HD 179218 4. Young stars Malbet, Grenoble (PI), 51 Oph 5. Resolving the dust shells surrounding red giants Preibisch, Bonn (PI), RR Sco, IRAS 17004-4119, Ringberg Workshop

  26. Science Demonstration time in P72 • SD2 will be carried out in P72 with MIDI only. Programs are approved by IC and represent about 6-7 nights of observing time. • They include: Debris disks, Alf Ori, Asymmetries and dust in AGB stars, Dusty disks in post-AGB binaries, NGC 1068, massive disks in YSO, R Mon, 2 HAeBe stars, and FU Ori. • Because of the source coordinates, SD2 will be split in two runs (November 6-9, 2003 and February 7-9, 2004) without and with FINITO/MACAO respectively. Ringberg Workshop

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