Download 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
PI PIXIS
BU 151AB
9/21/2008
Stars in Motion
Andor
iXon
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High Resolution Imaging and Binary Stars
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Stellar Masses.
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Mass-Luminosity Relation (MLR)
Initial Mass Function (IMF)
Statistics of binaries as clues to star formation and
galactic evolution.
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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.
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Orbits and masses.
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N
N
Binary stars.
Gravitation -->
orbit.
Traditionally very
hard to get good
masses.
q qq
r
r
r
r
r
r
r rr r
Need SIZE of orbit,
which means we
need the distance.
Hipparcos Satellite has done that job reasonably well …
Gaia, SIM will do much better!
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Example: Burnham 151AB
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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!
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BU 151AB Continued…
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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.
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Speckle: What’s New?
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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.
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Science
• Hipparcos doubles  Hipparcos BINARIES!
• Many tests of stellar evolution: put COMPONENTS of
binaries on the H-R diagram.
• Evolved Components.
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Solving the Dm problem with
CCDs.
(a)
Telescope Optics
(b)
Telescope Optics
CCD Array
CCD Array
“Tip” Speckle
Mirror Images
Speckle
Images
Tip-Tilt
Mirror
Row Shifts
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DSSI: The latest project…
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The Differential Speckle
Survey Instrument (DSSI)
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Two channel CCD-based
speckle camera, completed
in August, 2008
Observe two colors at the
same time (dichroic
beamsplitter inside).
Differential refraction
DSSI@WIYN
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DSSI Raw Frames, HIP 15737
692 nm
562 nm
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Color Differences
HIP 15737
(Primary is
K3III)
1 arcsec
HIP 101958
(Primary is
B9IV)
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McAlister 40 Below the
Diffraction Limit
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CCDs: good
photometry ->
speckle shapes.
Elongated
speckles: Could
be refraction,
could be a
component below
the diff. lim.
Two colors can
tell you which.
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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
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Wavelet-Based Image
Reconstruction
We can see fainter companion stars!
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iXon EMCCD Camera
512x512 pixels
 1,3,5 MHz
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iXon@WIYN
full frame
~17Hz
 128x128 subarray, use 33
Hz.
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Near Photon-Counting Performance at >90% QE!!
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A sample result:
RYTSI+iXon @ WIYN
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LP 439-387
Primary Mag.
=15.7
 Secondary Mag.
=16.0
 Sep ~ 0.8”
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About 40
seconds of data.
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iXon and Kepler
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Kepler: Satellite to
detect Earthlike
exoplanets
through transits.
iXon set-up is
helping to screen
targets of interest
to Kepler for
binarity.
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11.5-mag Kepler comparison
star shown to be binary at WIYN,
June 2008.
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Conclusions
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What are we waiting for?
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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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