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Astrometry of Binary Stars: What Are We Waiting For?

Astrometry of Binary Stars: What Are We Waiting For?. Elliott Horch, Southern Connecticut State University. 1 arcsec. Andor iXon. PI PIXIS. BU 151AB. High Resolution Imaging and Binary Stars. Stellar Masses. Mass-Luminosity Relation (MLR) Initial Mass Function (IMF)

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Astrometry of Binary Stars: What Are We Waiting For?

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  1. Astrometry of Binary Stars:What Are We Waiting For? Elliott Horch, Southern Connecticut State University 1 arcsec Andor iXon PI PIXIS BU 151AB Stars in Motion

  2. High Resolution Imaging and 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 and updates. • Post-formation environment. • Future projects such as SIM, GAIA: a very important development for binary star research. Stars in Motion

  3. 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. Hipparcos Satellite has done that job reasonably well … Gaia, SIM will do much better! Stars in Motion

  4. Example: Burnham 151AB • An exquisite orbit! • dP/P = 0.00041 • da/a = 0.00137 • Hipparcos distance ~30 pc • dp/p = 0.02628 • Gaia: dp/p ~ 0.0006. Then you’ll get great masses! Stars in Motion

  5. BU 151AB Continued… • H-R diagram with Y2 isochrones at right. • Speckle binaries with good magnitude/ color information of components can be excellent tests of stellar evolution. • We want to make many plots like this! • With evolved components, one can derive good ages. Stars in Motion

  6. Speckle: What’s New? • Instrumentation/Data Analysis • CCDs for good differential photometry (and of course astrometry too!) • EMCCDs: near photon-counting performance at >90% QE • Linear detectors mean more possibilities in terms of reduction algorithms. • Science • Hipparcos doubles  Hipparcos BINARIES! • Many tests of stellar evolution: put COMPONENTS of binaries on the H-R diagram. • Evolved Components. Stars in Motion

  7. (b) (a) Telescope Optics Telescope Optics CCD Array CCD Array “Tip” Mirror Speckle Images Speckle Images Tip-Tilt Mirror Row Shifts Solving the Dm problem with CCDs. Stars in Motion

  8. DSSI: The latest project… Stars in Motion

  9. The Differential Speckle Survey Instrument (DSSI) • Two channel CCD-based speckle camera, completed in August, 2008 • Observe two colors at the same time (dichroic beamsplitter inside). • Differential refraction DSSI@WIYN Stars in Motion

  10. DSSI Raw Frames, HIP 15737 692 nm 562 nm Stars in Motion

  11. Color Differences HIP 15737 (Primary is K3III) 1 arcsec HIP 101958 (Primary is B9IV) Stars in Motion

  12. McAlister 40 Below the Diffraction Limit • CCDs: good photometry -> speckle shapes. • Elongated speckles: Could be refraction, could be a component below the diff. lim. • Two colors can tell you which. Stars in Motion

  13. DSSI Result: Analytic Continuation 562 nm 692 nm E E N N 1 arcsec 1 arcsec HIP 6966 = A 1910AB Separation = 0.175 arcsec, position angle = 187o, V=6.77, Spectral Type = A0 Stars in Motion

  14. Wavelet-Based Image Reconstruction We can see fainter companion stars! Stars in Motion

  15. iXon EMCCD Camera • 512x512 pixels • 1,3,5 MHz • full frame ~17Hz • 128x128 sub- array, use 33 Hz. iXon@WIYN Near Photon-Counting Performance at >90% QE!! Stars in Motion

  16. A sample result: RYTSI+iXon @ WIYN • LP 439-387 • Primary Mag. =15.7 • Secondary Mag. =16.0 • Sep ~ 0.8” • About 40 seconds of data. Stars in Motion

  17. iXon and Kepler • Kepler: Satellite to detect Earthlike exoplanets through transits. • iXon set-up is helping to screen targets of interest to Kepler for binarity. 11.5-mag Kepler comparison star shown to be binary at WIYN, June 2008. Stars in Motion

  18. Conclusions • What are we waiting for? • We’ve got great instrumentation for speckle that is significantly more capable than in the past! • We can’t yet reap all the astrophysical benefits of these observations. We still need better distances, even to many “nearby” systems. • Bill van Altena has been a tireless supporter, advocate, and all-around cheerleader of this work. • Thank you Bill!! Stars in Motion

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