Studying Binary Stars a Few Photons at a Time

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Studying Binary Stars a Few Photons at a Time

• Elliott Horch, CIS

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Astronomy
Stars are
very
VERY
VERY
cool.
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What do we want to know about stars?

• How do they form? How much matter is needed? Are
  planets involved?
• How do stars work?
• Do they change? How long do they live?
• Why do they appear in groups sometimes?
• What can they tell us about how the Galaxy
  formed?

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Whats going to help us out in answering those
questions?

• Mass
• Luminosity (total light output)
• Size (radius)
• Surface Temperature
• Age
• Heavy Metal Content (metallicity)
• etc.

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What do we think we know about stars?

• Energy production mechanisms
• Basic life cycle features
• Pulsation
• Spectral features

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What still confuses us?

• Details, details (Sigh.)
• e.g. how to calibrate luminosities, etc??
• Neutrinos
• Formation Processes
• Jumps in HR diagram
• etc.

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Masses and the MLR

• Theory Mass and luminosity are related.

Our favorite star!
0
log(L/Lsun)
0
log(M/Msun)
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Reality Large Uncertainties!
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Why are masses so hard to measure?

• Binary stars. Gravitation --gt orbit.

Okay, well how? Scales? Ha!
BUT need SIZE of orbit, which means we need the
distance.
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Why are distances so hard to measure?

• Parallax

Earth
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Our Home Galaxy
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Our Home Galaxy - The Comic Book Version
Globular Clusters
Disk
Bulge
Halo
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Two Populations

• Population I
• Disk dwellers
• metal rich
• Population II
• Halo dwellers
• metal poor

MLR
log(L/Lsun)
Pop I
0
Pop II
0
log(M/Msun)
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Imaging Binary Stars

• That 3 Atmosphere!!
• Blurs out star images, cant see both stars
  distinctly if theyre too close together.
• Related to twinkling.
• Telescopes and camera systems the rest of the
  optical system.
• Big telescopes can resolve closer pairs.
• Need high-speed cameras to freeze the
  twinkling.

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Why the atmosphere is such a bummer...
light
Atmosphere
Ground
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At Big Telescopes, Stars Speckle
integrated image
speckle images
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At Big Telescopes, Stars Speckle
integrated image
speckle images
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Speckling Binary Star
t0.00s
t0.05s
t0.10s
t0.15s
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Speckling Binary Star
t0.00s
t0.05s
t0.10s
t0.15s
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Speckling Binary Star
t0.00s
t0.05s
t0.10s
t0.15s
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Reminds me of...
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A Close Binary
t0.00s
t0.05s
t0.10s
t0.15s
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A Close Binary
t0.00s
t0.05s
t0.10s
t0.15s
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A Close Binary
t0.00s
t0.05s
t0.10s
t0.15s
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We can Beat the Atmosphere!!
1 arcsec
speckle analysis
long exposure
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KPNO
The WIYN Telescope

Kitt Peak, Arizona
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Inside the WIYN Dome

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Hipparcos (True) Binaries
W97
W98
W99.89
W99.02
W99
H91
C95
H91
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Space Telescope FGSs
single star
signal
double star
x
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Koesters Prism
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A Real FGS Transfer Function

• FGS will help us study Pop II binaries.
• Orbits
• Masses
• Luminosities
• Pop II MLR !!!!!!!
• Better Ages and Distances to Glob. Clusters!!!!

arcsec
-0.8
0.8
Henry et al. (1999)
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Conclusions

• Stars are interesting.
• Star images taken at big telescopes speckle.
• Interferometric imaging of binary stars helps us
  determine their masses and luminosities, which in
  turn helps us understand how they work.
• Speckle imaging from the ground.
• Fine Guidance Sensor data from the Hubble Space
  Telescope.