Date post: | 22-Dec-2015 |
Category: |
Documents |
View: | 215 times |
Download: | 1 times |
Stellar Astrophysics with the Keck Interferometer
PI: S. R. Kulkarni
Co-I’s: D. Sasselov, M. Konacki, B. Lane
Motivation
• Current stellar models– Current models are good to ~10% . Not good
enough even for cosmology.
• Problematic areas:• Convection• Helium abundance
Our Approach• V2 observations of Eclipsing Binaries
– Radial Velocity provides all but distance– KI provides distance
>> Derive all physical parameters
• Differential Phase for Bright Binaries– A range of targets, including G+M and Cepheid
binaries
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
CM Dra Model
• 21 V2 points, 5.8% scatter.• 2 = 1.2• Semi-Major Axis: 1.14
0.04 mas• Parallax: 65.3±2.2 mas• Systematic Plx Uncert: 0.2
mas (assuming 10 %K, actually smaller)
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!)
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
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.
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,)
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