Stellar Astrophysics with the Keck Interferometer

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Stellar Astrophysics with the Keck Interferometer

• PI S. R. Kulkarni
• Co-Is D. Sasselov, M. Konacki, B. Lane

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Motivation

• Current stellar models
• Current models are good to 10 . Not good enough
  even for cosmology.
• Problematic areas
• Convection
• Helium abundance

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Our Approach

• V2 observations of Eclipsing Binaries
• Radial Velocity provides all but distance
• KI provides distance
• gtgt Derive all physical parameters
• Differential Phase for Bright Binaries
• A range of targets, including GM and Cepheid
  binaries

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M-dwarf Eclipsing Binaries

• M-L-R relations for these stars are an issue of
  debate
• Radius from eclipses
• RV to set physical scale
• Inteferometer for distance

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YY Gem CU Cnc (First two runs)

• KI observations resolved the systems

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CM Dra Observations
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CM Dra Model

• 21 V2 points, 5.8 scatter.
• ?2 1.2
• Semi-Major Axis 1.14 ? 0.04 mas
• Parallax 65.32.2 mas
• Systematic Plx Uncert 0.2 mas (assuming 10 ?K,
  actually smaller)

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CU Cnc

• 29 V2 pts, 2 scatter.
• ?2 0.3
• Perhaps discrepant parallax from Hipparcos

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Near-Term Prospects

• With scans over 1-2 more nights on CM Dra we will
  have a very interesting parallax measurement.
• With scans over 2 more nights we can solve the
  orbits of YY Gem and CU Cnc.
• We have applied for matching Caltech time
• (TAC is meeting today!)

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Epilogue

• KI is now working very well for binary targets
• However, the slow speed of KI means that KI
  should be used sparingly for binary science
• Outrigger array would truly revolutionize stellar
  astrophysics

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Distance to Pleiades via AtlasX-P Pan, M. Shao
S. Kulkarni(Nature, in negotiating phase)

• Pleiades is a gold standard for intermediate mass
  stars, brown dwarfs and Cepheid distance scale
• Hipparcos team published distance to Pleiades
• D 118 /- 4 pc
• Traditional distance (color-mag diagram)
• D 131 /- 3 pc
• Hipparcos result generated lively controversy.

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Orbit of Atlas

• P(orbit) 291 day
• a 13 mas
• e 0.245
• Inclination108d

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Distance via Keplers 3rd law
a3 d3 a3 (m1m2)P2
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Backup Slides
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Additional Visibility Targets

• There are many more systems to choose from, e.g.
• UU Cnc, an eclipsing K4 II system thought to have
  mass transfer
• Open cluster binaries ( vB22, attack issues of
  Y,?)

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Predicted Mesurement Precision for CU Cnc (GJ
2069A)
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Cepheid Binaries

• Binary companions hotter than primary, e.g. U
  Aql F8Ib B7V
• Very difficult to resolve (or even detect) with
  other methods
• Pulsation provides redundant signal

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Predicted Differential Phase Signal for U Aql
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PTI results

• We have ongoing work at PTI resolving binaries in
  open clusters such as the Hyades

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Predicted Visibility Evolution for YY Gem
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Predicted Measurement Precision for YY Gem