Astrometry of Binary Stars: What Are We Waiting For? Elliott Horch, Southern Connecticut State University 9/21/20081Stars in Motion BU 151AB 1 arcsec Andor iXon PI PIXIS

9/21/20082 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

9/21/20083 Orbits and masses. Binary stars. Gravitation --> orbit. 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. Hipparcos Satellite has done that job reasonably well … Gaia, SIM will do much better! Stars in Motion

Example: Burnham 151AB An exquisite orbit! P/P = a/a = Hipparcos distance ~30 pc  = Gaia:  ~ Then you’ll get great masses! 9/21/2008Stars in Motion4

BU 151AB Continued… H-R diagram with Y 2 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. 9/21/2008Stars in Motion5

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. 9/21/20086Stars in Motion

9/21/20087 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) Stars in Motion

9/21/20088 DSSI: The latest project… Stars in Motion

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 9/21/20089Stars in Motion

DSSI Raw Frames, HIP /21/2008Stars in Motion nm 562 nm

Color Differences 9/21/200811Stars in Motion HIP (Primary is K3III) HIP (Primary is B9IV) 1 arcsec

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. 9/21/2008Stars in Motion12

DSSI Result: Analytic Continuation 562 nm692 nm N EE N 1 arcsec HIP 6966 = A 1910AB Separation = arcsec, position angle = 187 o, V=6.77, Spectral Type = A0 9/21/200813Stars in Motion

9/21/ Wavelet-Based Image Reconstruction We can see fainter companion stars! Stars in Motion

iXon EMCCD Camera 512x512 pixels 1,3,5 MHz full frame ~17Hz 128x128 sub- array, use 33 Hz. 9/21/2008Stars in Motion15 Near Photon-Counting Performance at >90% QE!!

A sample result: WIYN LP Primary Mag. =15.7 Secondary Mag. =16.0 Sep ~ 0.8” About 40 seconds of data. 9/21/2008Stars in Motion16

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. 9/21/2008Stars in Motion mag Kepler comparison star shown to be binary at WIYN, June 2008.

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!! 9/21/2008Stars in Motion18