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Part I: High Resolution Imaging with Speckle Interferometry

H 19206. Part I: High Resolution Imaging with Speckle Interferometry. Elliott Horch, University of Massachusetts Dartmouth, USA. Speckle Often Means Binary Stars. Stellar Masses. Mass-Luminosity Relation (MLR) Initial Mass Function (IMF)

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Part I: High Resolution Imaging with Speckle Interferometry

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  1. H 19206 Part I: High Resolution Imaging with Speckle Interferometry • Elliott Horch, University of Massachusetts Dartmouth, USA Yale Astrometry Workshop / Horch 1

  2. Speckle Often Means Binary Stars • Stellar Masses. • Mass-Luminosity Relation (MLR) • Initial Mass Function (IMF) • Statistics of binaries as clues to star formation and galactic evolution. • Ghez et al, Leinert et al. Recent models of Bate, etc. • Duquennoy & Mayor. • Post-formation environment. • Future projects such as SIM, GAIA: a very important development for binary star research. Yale Astrometry Workshop / Horch 1

  3. Aperture Synthesis Image Aperture Point Source Yale Astrometry Workshop / Horch 1

  4. Aperture Synthesis Image Aperture Binary Pt Src Yale Astrometry Workshop / Horch 1

  5. Why the atmosphere is kind of a bummer… Light Atmosphere Ground Yale Astrometry Workshop / Horch 1

  6. Aperture Image “speckle pattern” exposure time ~0.01s (w,z) (x,y) The atmosphere dictates the point spread function Yale Astrometry Workshop / Horch 1

  7. Make a “movie” Each frame is a unique speckle pattern Analyze data frame by frame. “Passive” technique Speckle Interferometry in a Nutshell Yale Astrometry Workshop / Horch 1

  8. Binary Star Images t=0.00s t=0.05s t=0.10s t=0.15s Yale Astrometry Workshop / Horch 1

  9. A smaller separation t=0.00s t=0.05s t=0.10s t=0.15s Yale Astrometry Workshop / Horch 1

  10. A binary star is a simple image morphology Image Object AA BA SPECKLE IMAGE RECONSTRUCTION: Get back to BA picture from many AA images using image processing techniques. Yale Astrometry Workshop / Horch 1

  11. Autocorrelation Analysis FT Data of the binary Data of a Single star Yale Astrometry Workshop / Horch 1

  12. Power spectrum of a binary fit residuals data Power spectrum cannot give you an image: - directed vector autocorrelation - image reconstruction (bispectrum) Yale Astrometry Workshop / Horch 1

  13. Bispectral Analysis Define triple correlation: FT is called the bispectrum, can be written: Sequence of speckle data frames contains diff. limited info: Let u1 = u, u2 = Du, where Du is small. Then, consider only the phase. Can show a point source should have zero phase. Then, Yale Astrometry Workshop / Horch 1

  14. Bispectral Analysis, cont’d Well, so Thus, the bispectrum contains phase derivative information! By integrating, we obtain the phase, which can be combined with the modulus to obtain a diffraction-limited estimate of . Yale Astrometry Workshop / Horch 1

  15. Reconstructed Images from RYTSI Data: Examples. HIP 098055 = YR 2 HIP 101769 = BU 151 HIP 085209 = HD 157948 HIP 021730 = BU 1295AB + STF 566AB-C Yale Astrometry Workshop / Horch 1

  16. The “delta-m” problem • “[Determining magnitude differences] is very sensitive to such factors as seeing conditions, stellar brightness, binary separation, and camera magnification; it is further complicated by the lack of photo- metric standards among close visual binaries. These factors force us to assume error bars of about 0.5 mag for our estimates of Dm.” • ---Hartkopf et al. (1996) Yale Astrometry Workshop / Horch 1

  17. Why is it so hard? • Two fundamental reasons: • Atmospherics: the isoplanatic patch • The detector: “microchannel saturation” • How to improve things • Observe from a site with good seeing • Do NOT use an intensified camera. Yale Astrometry Workshop / Horch 1

  18. Microchannel Saturation hn e- Yale Astrometry Workshop / Horch 1

  19. Part I Conclusion: Speckle circa 1996 • All of the above methodology was known and well-understood. • Because of the delta-m problem, speckle was viewed primarily as an astrometric technique, not useful for determining luminosities or effective temperatures of components of binary star systems. • ~100 orbits substantially refined with speckle. • Push toward adaptive optics as a solution to the Dm problem. • Await Hipparcos distances (1997). Yale Astrometry Workshop / Horch 1

  20. Part II: Observing binaries from the Ground, HST, and Hipparcos Yale Astrometry Workshop / Horch 1

  21. Main Astrometric Techniques • Speckle, as we’ve just seen • Photometry problem solved. • Adaptive Optics • Good results here. • Impact of Hipparcos and Tycho measures. • Binary statistics. • Long Baseline Optical Interferometry. • Actually, we’ll wait until the next talk. • Fine Guidance Sensors on HST. • A space interferometer that’s been in operation for years. (Obviously others that we will not mention…) Yale Astrometry Workshop / Horch 1

  22. Binary stars. Gravitation --> orbit. Traditionally very hard to get good masses. N q N N N N N N N N N N q r q r r r r r r r r r r Orbits and masses. Need SIZE of orbit, which means we need the distance. Yale Astrometry Workshop / Horch 1

  23. Let’s dream! • Can determine the orbit, total magnitude, magnitude difference, parallax, and spectrum. • From these, derive masses, luminosities, effective temperatures, common metallicity (seven params). • That’s more than sufficient to constrain standard stellar models (M1, M2, Y, Z). • Age information, at least in some cases. • Chemical evolution (DY/DZ)! • Indirect information about star formation, environment through statistics. Yale Astrometry Workshop / Horch 1

  24. Definitions • One can completely characterize the true relative orbit with seven orbital parameters (observables): • Period (P) • Semi-major axis (angular measure) (a) • Inclination of orbit to the plane of the sky (i) • Position angle of ascending node (W) • Time of pariastron passage (T) • Eccentricity of orbital ellipse (e) • Angle between line of nodes and major axis in plane of the true orbit (w) • Line of nodes: line of intersection between orbital plane and plane of the sky. Yale Astrometry Workshop / Horch 1

  25. Cheat sheet for calculating an orbit (Thiele) Computer Prog.: If you have a series of (r, q, t) data, pick your seven orbital params, calculate predicted (r, q, t), iterate to find min in chi-squared. Yale Astrometry Workshop / Horch 1

  26. Sadly, astrometry can’t do it all • “Visual” binaries: P, a, p and Kepler’s harmonic law yield mass sum, not individual masses. • If system is also a single-lined spectroscopic binary, then you can get individual masses. • If the system is also a double-lined spectroscopic binary, then you don’t need the parallax and you still get individual masses. • However, masses must be combined with other measurements anyway to yield meaningful astrophysics. (luminosities, metallicity, etc) Yale Astrometry Workshop / Horch 1

  27. (b) (a) Telescope Optics Telescope Optics CCD Array CCD Array “Tip” Mirror Speckle Images Speckle Images Tip-Tilt Mirror Row Shifts Speckle: Solving the Dm problem with CCDs. Yale Astrometry Workshop / Horch 1

  28. A New Speckle Camera The RIT-Yale Tip-tilt Speckle Imager “RYTSI” Yale Astrometry Workshop / Horch 1

  29. A RYTSI Frame • Extract individual images and stack (C. Rothkopf, H. Riedel) • Diffraction-limited image reconstructions. • High-precision Astrometry. • In addition, magnitude differences. Yale Astrometry Workshop / Horch 1

  30. Astrometric Precision at WIYN (Two minute observations) Yale Astrometry Workshop / Horch 1

  31. Photometric Precision with CCD Speckle at WIYN (Two minute observations) Yale Astrometry Workshop / Horch 1

  32. RYTSI+Mini Mosaic Imager • February 2004 • More than 900 speckle images per frame! MiniMo = two 2Kx4K CCDs Yale Astrometry Workshop / Horch 1

  33. MiniMo does more… H 20745 (seeing 1 arcsec) Camera: MiniMosaic Separation: 0.38 arcsec Prim. Magn.: 11.1 Sec. Magn.: 11.4 Filter: V Comments: Very faint for speckle; could not be observed with the older CCD. Primary Star Secondary Star Increase in S/N ~3.4x, Magnitude ~11.3 Yale Astrometry Workshop / Horch 1

  34. Active Speckle Programs, an incomplete list… • Observatories y Telescopes used • Calar Alto, Spain (Docobo, Andrade, Ling, Tazmanian, Prieto, colaboradores) ICCD • SAO, Russia (Balega, Balega, Hofmann, Weigelt, collaborators) • Pic du Midi/Brera, France/ Italy (PISCO instrument: Scardia, Prieur, Aristidi, collaborators) • India (S.K. Saha, collaborators) • WIYN Telescope, Kitt Peak, USA (Horch, van Altena, collaborators) • Naval Observatory in Washington, USA. (Mason, Hartkopf, collaborators) • IR Speckle (Ghez, Woitas, etc) Yale Astrometry Workshop / Horch 1

  35. Adaptive Optics • Program of binary star observations by the CHARA group and collaborators since 1996. • Thesis: Lewis Roberts. • Addressing same issues as we’ve just seen with CCD speckle, same kinds of results: place components on H-R diagram. • Astrometry appears comparable to speckle. • Photometric precision per observation: a few hundredths of a magnitude. • NOT easy: take many short (~1s) exposures with AO system on. Be careful for systematics in the PSF. Non-isoplanicity, scintillation are factors that limit precision. Yale Astrometry Workshop / Horch 1

  36. A few contributions of FGS (TRANS Mode) • Orbits and masses of binary stars. • Mass-luminosity relation for low masses • Franz, Henry, collaborators • Binaries in the Hyades. • Franz and collaborators • Characterization of asteroids. • Binaries with low metallicity. • Horch, Franz, collaborators; • Osborn & Hershey Yale Astrometry Workshop / Horch 1

  37. “Pickles” Three FGS Fields Of View. NOTE: Many FGS figures Taken from The FGS Instrument Handbook. FGS IHB Yale Astrometry Workshop / Horch 1

  38. Selection of Stars within the Pickle Yale Astrometry Workshop / Horch 1

  39. Filter Transmission Curves, FGS1r Yale Astrometry Workshop / Horch 1

  40. …On to the Detectors • QE at 700nm is 2%, 18% at 400nm. • Between these limits, QE curve is more or less linear. • 40 measures per second. • Each FGS has four PMTs: two for x, two for y. Yale Astrometry Workshop / Horch 1

  41. A B The essential part of the operation TRANS mode Define the “transfer function” as a.k.a. “S-curve” Yale Astrometry Workshop / Horch 1

  42. Comparison between PC and FGS Niemela et al. 1998 (FGS Simulation) Separation = 168 mas Yale Astrometry Workshop / Horch 1

  43. FGS can do more… (PC simulation) (FGS simulation) Separation = 70 mas It is possible to measure separations down to 10-15 mas with FGS. Yale Astrometry Workshop / Horch 1

  44. Basic Characteristics • POS or TRANS mode: POS=position, TRANS= transfer. • One can measure separations down to 10-15 mas. • (depends on system magnitude, etc.) • Can observe binaries of magnitude down to 16. • 1-D scans in two perpendicular axes, not images. • The S-curve is an interference pattern. Yale Astrometry Workshop / Horch 1

  45. Conclusions • CCD speckle yields good Dm’s, optimal for survey work. • Adaptive Optics: Also solves Dm problem of older speckle; higher observing overhead, but apparently more precise. • FGS: a unique instrument for binary star work. • One can measure binaries that are both faint and have small separation. Dm up to 5. • It now seems possible, via Fourier analysis, to obtain color difference estimates of the components from FGS scans. • Hipparcos and Tycho: an invaluable resource for binary statistics for stars near the Sun. Yale Astrometry Workshop / Horch 1

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