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Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

DRM #2 - M. K ü rster , T. Herbst, E. Meyer, B. Goldman. Tom‘s title: Panoramic Interferometric Astrometr y with LINC-NIRVANA . My title: LINC-NIRVANA Design Reference Mission #2. Astrometric Follow-up of Extrasolar Planets with Radial-velocity Derived Orbits.

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Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

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  1. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman Tom‘s title:Panoramic Interferometric Astrometry with LINC-NIRVANA. My title:LINC-NIRVANA Design Reference Mission #2. Astrometric Follow-up of Extrasolar Planets with Radial-velocity Derived Orbits Goal: Determine the mass of the companion and thereby its nature: planet vs. brown dwarf vs. star Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  2. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman Team: M. Kürster - project definition and strategy, sample definition T. Herbst - project definition, instrument performance E. Meyer - pilot studies: (a) astrometric precision in MAD data (b) astrometric orbit determination with NaCo B. Goldman - astrometric reference object prediction Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  3. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman • Extrasolar planets discovered by RVs • Stellar RV change (few m/s) due to reflex motion • of star around star-planet barycenter • Most orbital parameters are known: P, e, To, ω, K f(m) • Missing orbital parameters:Ω, i •  only minimum companion mass •  nature of companion unknown •  employ astrometry … Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  4. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman • Astrometric follow-up • Astrometric determination of stellar reflex orbit • Keep RV-derived orbital parameters fixed – they have high precision • Solve for: Ω, i, αo, δo, dα/dt, dδ/dt, π(7 parameters) Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  5. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman • Astrometric follow-up • Minimum astrometric effect: • ± semi-minor axis angle: β = arctan(b/d) • b = a (1-e2)1/2 • Observer •  can be predicted from RV solution • and stellar distance d Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  6. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman Astrometry with LINC-NIRVANA Need high precision position measurements in 2 coordinates, Goal: 1/50 pixel precision = 0.1 mas  Ideal, but not strictly required: At every epoch observe at 2 parallactic angles roughly perpendicular to each other P = years: one night  one epoch  Point sources: employ PSF fitting etc. - do not employ image deconvolution, avoid deconvolution artefacts Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  7. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman RV-determined candidates - Astrometric signal vs. RV signal * But lower signal-to-noise  larger RV measurement error Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  8. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman • Target selection criteria: • Requirements: • Visibility from Mt. Graham: δ ≥ -27o, better: δ ≥ 0o • Semi-minor axis angle β ≥ 0.2 mas = 1/25 pixel • Astrometric reference objects in the FoV of 10.5“ x 10.5“ • Other considerations: • Fringe tracking star = science target • Suitable asterism for MCAO stars • (or is LINC mode sufficient = single on-axis AO guide star?) • Bright science target saturates detector even in narrow-band filter: •  solutions: just saturate and work on outer frings of the PSF • fabricate a specially masked filter Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  9. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  10. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman • Target selection criteria: • Requirements: • Visibility from Mt. Graham: δ ≥ -27o, better: δ ≥ 0o • Semi-minor axis angle β ≥ 0.2 mas = 1/25 pixel • Astrometric reference objects in the FoV of 10.5“ x 10.5“ • Status April 2008: • Of ~235 RV-discovered planetary systems • 16 fulfill δ ≥ 0o and β ≥ 0.2 mas • 10 fulfill 0o ≥ δ ≥ -27o and β ≥ 0.2 mas • Astrometric reference objects in the FoV ? Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  11. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman Target list: Expected number of stars in FoV with K<21.5 or J<23 predicted from Besançon (2000) models of the galaxy Depending on employed model, 1 - 2 extragalactic objects can be added Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  12. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman The best candidates: HR 7670 = HD 190360 GJ 4052 = HD 168443 λ = 67o, β = -1o λ = 21o, β = +3o MCAO reference stars: outer circle 6´(GWS), inner circle 2´(MHWS) Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  13. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman • Work in progress: • Detector saturation limit as a function of • (a) stellar K-magnitude • (b) science filter • (c) detector integration time (DIT) • (2)Exposure times for an astrometric precision of 1/50 pixel as a function of • (a) K-magnitude of astrometric reference star • (b) science filter • (3)Devise strategies against target saturation, e.g. • (a) keep DIT short and • use a narrow band filter (faint targets) • (b) just saturate and work on PSF wings (medium bright) • (c) use a filter with an attenuating mask (bright targets) - Min. DIT = 1.4 s - Filter: narrow-K‘ (1/20 throughput) Saturation limit: J = 8.6, K = 6.6  1 star in target list Astrometric precision in 1h: J = 23: ~0.07mas K = 21.5: ~0.12mas Plus: unknown systematics Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  14. Any questions? - Feel free to ask! DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman • Pilot studies – PhD thesis E. Meyer • Astrometric precision in MAD layer-oriented MCAO data: • Thanks to • R. Ragazzoni, • C. Arcidiacono • Globular cluster • NGC 6388 • 5 MCAO stars: • V=13.6-14.5 • Strehl in 1‘x1‘ FoV: • 0.160-0.205 L-N FoV:: Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

  15. DRM #2 - M. Kürster, T. Herbst, E. Meyer, B. Goldman Pilot studies – PhD thesis E. Meyer (b) Astrometric orbit determination with NaCo : Chance encounter of the M dwarf-Brown dwarf system GJ 1046 (Kürster et al. 2008) with a background star separated by 29“ βmin = 1.85 mas P = 169 d mmin = 27 MJup  Poster outside Second generation science with the LBT, Ringberg, 2008-07-15, M. Kürster

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