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1/9/2003Ringberg Workshop1 Recent science results from VLTI commissioning Francesco Paresce European Southern Observatory.

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Presentation on theme: "1/9/2003Ringberg Workshop1 Recent science results from VLTI commissioning Francesco Paresce European Southern Observatory."— Presentation transcript:

1 1/9/2003Ringberg Workshop1 Recent science results from VLTI commissioning Francesco Paresce European Southern Observatory

2 1/9/2003Ringberg Workshop2 P70 VINCI Shared 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

3 1/9/2003Ringberg Workshop3 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

4 1/9/2003Ringberg Workshop4 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

5 1/9/2003Ringberg Workshop5 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

6 1/9/2003Ringberg Workshop6 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 Cars 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

7 1/9/2003Ringberg Workshop7 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

8 1/9/2003Ringberg Workshop8 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

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10 1/9/2003Ringberg Workshop10 Eta Carinae: some basic facts In Tr 16 in Carina nebula (NGC 3372,) located at 2.5 +/- 0.3 kpc {M HII ~ 10 4 M ~ 10 3 x Orion} Super massive LBV: ~ 100 M Super luminous: 3-5x10 6 L (most lum. in MW) now but ~30 x 10 6 L at outburst (2 nd brightest object in sky) Super hot: 15-40 x 10 3 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

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12 1/9/2003Ringberg Workshop12 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?

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15 1/9/2003Ringberg Workshop15 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.

16 1/9/2003Ringberg Workshop16 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.

17 1/9/2003Ringberg Workshop17 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

18 1/9/2003Ringberg Workshop18 Very, very high resolution interferometry with VLTI (1mas) Size of source = 5mas Responsible for 180 Jy emission from an area of ~10 AU 2 at 2.4 kpc For 2 mags of extinction, T min ~ 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)!

19 1/9/2003Ringberg Workshop19 Analysis & Results Wind model assumptions: Spherical star with dense, ionized and isothermal stellar wind Gas accelerates from initial v 0 to terminal velocity v as v(r) = v 0 +(1-R * /r)(v -v 0 ) Wind is clumpy: f = / ρ Main sources of opacity: f-f and f-b absorption and Thomson scattering Using HST/STIS long slit spectra that give: M dot /f = 3.16 10 -3 M /yr (dashed line) Results: M dot = 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)

20 1/9/2003Ringberg Workshop20 But, its 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.

21 1/9/2003Ringberg Workshop21 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, M dot will be ~ 8x the non rotating case Wind asymmetries assumed to explain long slit HST results (see figure above) are consistent with this scenario.

22 1/9/2003Ringberg Workshop22 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 (B proj ) 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.

23 1/9/2003Ringberg Workshop23 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.

24 1/9/2003Ringberg Workshop24 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 v eq =v crit and i=90° was also used Results: Be star models dont 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 dont understand Be stars!

25 1/9/2003Ringberg Workshop25 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,

26 1/9/2003Ringberg Workshop26 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.

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