Astrometry of Binary Stars: What Are We Waiting For?

Astrometry of Binary Stars:What Are We Waiting For?

Elliott Horch, Southern Connecticut State University

9/21/2008 1Stars in Motion

BU 151AB

1 arcsec

AndoriXon

PI PIXIS

9/21/2008 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

9/21/2008 3

Orbits and masses.

Binary stars. Gravitation --> orbit.

Traditionally very hard to get good masses.

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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 = 0.00041 a/a = 0.00137 Hipparcos distance

~30 pc = 0.02628 Gaia: ~ 0.0006.

Then you’ll get great masses!

9/21/2008 Stars in Motion 4

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.


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.


9/21/2008 7

Solving the m problem with CCDs.

CCD Array

Tip-Tilt Mirror

Telescope Optics

SpeckleImages

(b)

CCD Array

“Tip” Mirror

Telescope Optics

SpeckleImages

Row Shifts

(a)

Stars in Motion

9/21/2008 8

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


DSSI@WIYN

DSSI Raw Frames, HIP 15737


692 nm562 nm

Color Differences


HIP 15737(Primary isK3III)

HIP 101958(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.


DSSI Result: Analytic Continuation

562 nm 692 nm

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1 arcsec 1 arcsec

HIP 6966 = A 1910AB Separation = 0.175 arcsec, position angle = 187o, V=6.77,Spectral Type = A0


9/21/2008 14

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.


Near Photon-Counting Performance at >90% QE!!

iXon@WIYN

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.


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 comparisonstar 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!!


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Astrometry of Binary Stars: What Are We Waiting For?