19 July 2005Yale Astrometry Workshop / Horch 11 Part I: High Resolution Imaging with Speckle Interferometry Elliott Horch, University of Massachusetts Dartmouth, USA H 19206

19 July 2005Yale Astrometry Workshop / Horch 12 Speckle Often Means Binary Stars n Stellar Masses. n Mass-Luminosity Relation (MLR) n Initial Mass Function (IMF) n Statistics of binaries as clues to star formation and galactic evolution. ä Ghez et al, Leinert et al. Recent models of Bate, etc. ä Duquennoy & Mayor. ä Post-formation environment. n Future projects such as SIM, GAIA: a very important development for binary star research.

19 July 2005Yale Astrometry Workshop / Horch 13 Aperture Synthesis Point Source Aperture Image

19 July 2005Yale Astrometry Workshop / Horch 14 Aperture Synthesis Aperture Image Binary Pt Src

19 July 2005Yale Astrometry Workshop / Horch 15 Why the atmosphere is kind of a bummer… Ground Atmosphere Light

19 July 2005Yale Astrometry Workshop / Horch 16 The atmosphere dictates the point spread function (w,z) Aperture (x,y) Image “speckle pattern” exposure time ~0.01s

19 July 2005Yale Astrometry Workshop / Horch 17 Speckle Interferometry in a Nutshell l Make a “movie” l Each frame is a unique speckle pattern l Analyze data frame by frame. l “Passive” technique

19 July 2005Yale Astrometry Workshop / Horch 18 Binary Star Images t=0.00s t=0.05s t=0.10s t=0.15s

19 July 2005Yale Astrometry Workshop / Horch 19 A smaller separation t=0.00s t=0.05s t=0.10s t=0.15s

19 July 2005Yale Astrometry Workshop / Horch 110 A binary star is a simple image morphology BA AA Image Object SPECKLE IMAGE RECONSTRUCTION: Get back to BA picture from many AA images using image processing techniques.

19 July 2005Yale Astrometry Workshop / Horch 111 Autocorrelation Analysis Data of the binary Data of a Single star FT

19 July 2005Yale Astrometry Workshop / Horch 112 Power spectrum of a binary data fitresiduals Power spectrum cannot give you an image: - directed vector autocorrelation - image reconstruction (bispectrum)

19 July 2005Yale Astrometry Workshop / Horch 113 Bispectral Analysis FT is called the bispectrum, can be written: Define triple correlation: Sequence of speckle data frames contains diff. limited info: Let u 1 = u, u 2 =  u, where  u is small. Then, consider only the phase. Can show a point source should have zero phase. Then,

19 July 2005Yale Astrometry Workshop / Horch 114 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.

19 July 2005Yale Astrometry Workshop / Horch 115 Reconstructed Images from RYTSI Data: Examples. HIP = BU 1295AB + STF 566AB-C HIP = BU 151 HIP = YR 2 HIP = HD

19 July 2005Yale Astrometry Workshop / Horch 116 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  m.” ---Hartkopf et al. (1996)

19 July 2005Yale Astrometry Workshop / Horch 117 Why is it so hard? n Two fundamental reasons: ä Atmospherics: the isoplanatic patch ä The detector: “ microchannel saturation ” n How to improve things ä Observe from a site with good seeing ä Do NOT use an intensified camera.

19 July 2005Yale Astrometry Workshop / Horch 118 Microchannel Saturation h e-

19 July 2005Yale Astrometry Workshop / Horch 119 Part I Conclusion: Speckle circa 1996 n All of the above methodology was known and well-understood. n 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. n ~100 orbits substantially refined with speckle.  Push toward adaptive optics as a solution to the  m problem. ä Await Hipparcos distances (1997).

19 July 2005Yale Astrometry Workshop / Horch 120 Part II: Observing binaries from the Ground, HST, and Hipparcos

19 July 2005Yale Astrometry Workshop / Horch 121 Main Astrometric Techniques n Speckle, as we’ve just seen ä Photometry problem solved. n Adaptive Optics ä Good results here. n Impact of Hipparcos and Tycho measures. ä Binary statistics. n Long Baseline Optical Interferometry. ä Actually, we’ll wait until the next talk. n Fine Guidance Sensors on HST. ä A space interferometer that’s been in operation for years. (Obviously others that we will not mention…)

19 July 2005Yale Astrometry Workshop / Horch 122 Orbits and masses. n Binary stars. Gravitation --> orbit. n Traditionally very hard to get good masses. N   N   N   N  N  N  N  N  N  N  N  Need SIZE of orbit, which means we need the distance.

19 July 2005Yale Astrometry Workshop / Horch 123 Let’s dream! n Can determine the orbit, total magnitude, magnitude difference, parallax, and spectrum. n From these, derive masses, luminosities, effective temperatures, common metallicity (seven params). n That’s more than sufficient to constrain standard stellar models (M 1, M 2, Y, Z). n Age information, at least in some cases. Chemical evolution (  Y/  Z)! n Indirect information about star formation, environment through statistics.

19 July 2005Yale Astrometry Workshop / Horch 124 Definitions n One can completely characterize the true relative orbit with seven orbital parameters (observables): ä Period (P) ä Semi-major axis (angular measure) (a) ä Inclination of orbit to the plane of the sky (i)  Position angle of ascending node (  ) ä Time of pariastron passage (T) ä Eccentricity of orbital ellipse (e)  Angle between line of nodes and major axis in plane of the true orbit (  ) ä Line of nodes: line of intersection between orbital plane and plane of the sky.

19 July 2005Yale Astrometry Workshop / Horch 125 Cheat sheet for calculating an orbit (Thiele) Computer Prog.: If you have a series of ( , , t) data, pick your seven orbital params, calculate predicted ( , , t), iterate to find min in chi-squared.

19 July 2005Yale Astrometry Workshop / Horch 126 Sadly, astrometry can’t do it all “Visual” binaries: P, a,  and Kepler’s harmonic law yield mass sum, not individual masses. n If system is also a single-lined spectroscopic binary, then you can get individual masses. n If the system is also a double-lined spectroscopic binary, then you don’t need the parallax and you still get individual masses. n However, masses must be combined with other measurements anyway to yield meaningful astrophysics. (luminosities, metallicity, etc)

19 July 2005Yale Astrometry Workshop / Horch 127 Speckle: Solving the  m problem with CCDs. CCD Array Tip-Tilt Mirror Telescope Optics Speckle Images (b) CCD Array “Tip” Mirror Telescope Optics Speckle Images Row Shifts (a)

19 July 2005Yale Astrometry Workshop / Horch 128 A New Speckle Camera The R IT- Y ale T ip-tilt S peckle I mager “RYTSI”

19 July 2005Yale Astrometry Workshop / Horch 129 A RYTSI Frame n Extract individual images and stack (C. Rothkopf, H. Riedel) n Diffraction-limited image reconstructions. n High-precision Astrometry. n In addition, magnitude differences.

19 July 2005Yale Astrometry Workshop / Horch 130 Astrometric Precision at WIYN (Two minute observations)

19 July 2005Yale Astrometry Workshop / Horch 131 Photometric Precision with CCD Speckle at WIYN (Two minute observations)

19 July 2005Yale Astrometry Workshop / Horch 132 RYTSI+Mini Mosaic Imager n February 2004 n More than 900 speckle images per frame! MiniMo = two 2Kx4K CCDs

19 July 2005Yale Astrometry Workshop / Horch 133 MiniMo does more… H Secondary Star Primary Star 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. Increase in S/N ~3.4x, Magnitude ~11.3 (seeing 1 arcsec)

19 July 2005Yale Astrometry Workshop / Horch 134 Active Speckle Programs, an incomplete list… n Observatories y Telescopes used ä Calar Alto, Spain (Docobo, Andrade, Ling, Tazmanian, Prieto, colaboradores) ICCD ä SAO, Russia (Balega, Balega, Hofmann, Weigelt, collaborators) ä Pic du Midi/Brera, France/ Italy (PISCO instrument: Scardia, Prieur, Aristidi, collaborators) ä India (S.K. Saha, collaborators) ä WIYN Telescope, Kitt Peak, USA (Horch, van Altena, collaborators) ä Naval Observatory in Washington, USA. (Mason, Hartkopf, collaborators) ä IR Speckle (Ghez, Woitas, etc)

19 July 2005Yale Astrometry Workshop / Horch 135 Adaptive Optics n Program of binary star observations by the CHARA group and collaborators since n Thesis: Lewis Roberts. n Addressing same issues as we’ve just seen with CCD speckle, same kinds of results: place components on H-R diagram. n Astrometry appears comparable to speckle. n Photometric precision per observation: a few hundredths of a magnitude. n 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.

19 July 2005Yale Astrometry Workshop / Horch 136 A few contributions of FGS (TRANS Mode) n Orbits and masses of binary stars. n Mass-luminosity relation for low masses ä Franz, Henry, collaborators n Binaries in the Hyades. ä Franz and collaborators n Characterization of asteroids. n Binaries with low metallicity. ä Horch, Franz, collaborators; ä Osborn & Hershey

19 July 2005Yale Astrometry Workshop / Horch 137 “Pickles” Three FGS Fields Of View. FGS IHB NOTE: Many FGS figures Taken from The FGS Instrument Handbook.

19 July 2005Yale Astrometry Workshop / Horch 138 Selection of Stars within the Pickle

19 July 2005Yale Astrometry Workshop / Horch 139 Filter Transmission Curves, FGS1r

19 July 2005Yale Astrometry Workshop / Horch 140 …On to the Detectors n QE at 700nm is 2%, 18% at 400nm. n Between these limits, QE curve is more or less linear. n 40 measures per second. n Each FGS has four PMTs: two for x, two for y.

19 July 2005Yale Astrometry Workshop / Horch 141 The essential part of the operation A B TRANS mode Define the “transfer function” as a.k.a. “S-curve”

19 July 2005Yale Astrometry Workshop / Horch 142 Comparison between PC and FGS Separation = 168 mas Niemela et al (FGS Simulation)

19 July 2005Yale Astrometry Workshop / Horch 143 FGS can do more… Separation = 70 mas (FGS simulation) (PC simulation) It is possible to measure separations down to mas with FGS.

19 July 2005Yale Astrometry Workshop / Horch 144 Basic Characteristics n POS or TRANS mode: POS=position, TRANS= transfer. n One can measure separations down to mas. ä (depends on system magnitude, etc.) n Can observe binaries of magnitude down to 16. n 1-D scans in two perpendicular axes, not images. n The S-curve is an interference pattern.

19 July 2005Yale Astrometry Workshop / Horch 145 Conclusions CCD speckle yields good  m’s, optimal for survey work. Adaptive Optics: Also solves  m problem of older speckle; higher observing overhead, but apparently more precise. n FGS: a unique instrument for binary star work.  One can measure binaries that are both faint and have small separation.  m up to 5. ä It now seems possible, via Fourier analysis, to obtain color difference estimates of the components from FGS scans. n Hipparcos and Tycho: an invaluable resource for binary statistics for stars near the Sun.