Robo-AO and Kepler
Nicholas M. Law, Tim Morton, Christoph Baranec, Reed Riddle, Ganesh Ravichandran, Carl Ziegler, John Asher Johnson, Shriharsh P. Tendulkar, Khanh Bui, Mahesh P. Burse, H. K. Das, Richard G. Dekany, Shrinivas Kulkarni, Sujit Punnadi, and A. N. Ramaprakash
The Astrophysical Journal, 791:35 (18pp), 2014 August 10
Christoph Baranec, Reed Riddle, Nicholas M. Law, A. N. Ramaprakash, Shriharsh Tendulkar, Kristina Hogstrom, Khanh Bui, Mahesh Burse, Pravin Chordia, Hillol Das, Richard Dekany, Shrinivas Kulkarni, and Sujit Punnadi
The Astrophysical Journal Letters, 790:L8 (6pp), 2014 July 20
- Autonomous laser adaptive optics imaging system
- Palomar Observatory 60-inch telescope (1.5 m)
- 200 objects per night
Detector / AO
8.6 fps readout
1.2 kHz control loop
90-100 Hz wavefront control
141-218 nm wavefront error
- 40 s to slew/point
- 40-42 s for laser acquisition
- 30-180 s on target
- Queue-based observing
- Optimizes schedule based on:
Compare to 5-35 min
- slew time
- telescope limits
- prior observing attempts
- satellite avoidance
200 targets / night
- Target selected from queue
- Slew, point, acquire target (80 s)
- Continuous readout for 30-180 s
- Calibrate, then shift each frame based on guide star
- Co-add shifted frames
8.6 frames / second
Single, nearly diffraction-limited image
PSF subtraction of each object to find blended neighbors.
Can detect 1/100 contrast at separations above 0.2".
Stretch to Peak
Stretch to 10%
What's it useful for?
Doesn't go as faint as Keck
but can target a lot of objects
and is cheap.
and lots of them.
> 3500 candidates ("KOIs")
< 3% confirmed
10%-15% may be false positives, e.g., blended transiting binaries
Properties of Systems
- Planet radius, mass, temperature
- Statistics of planetary systems
- Planetary systems in binaries different?
AO imaging key
Robo-AO will eventually target every KOI
Begin with representative sample
Should be constant
PSF model obtained from 20 KOIs observed under similar conditions on same night.
Only photon noise should remain.
Gold standard: Try to extract simulated companions for every source
Next best: Try to extract simulated companions for representative sample
53 companions (43 new)
Earlier simulated sensitivity
Which star was transited? How deep was the transit for that star?
Transit depth and planet radius:
If planet transits target star,
If planet transits companion star,
Fraction of light from transited star
Determine from magnitude difference
B is in background
- Four planet candidates
- Jupiter-like candidate with 15.4-day period
- Unique in multi-planet systems
- Five planet candidates
- Two in 2:1 resonance, separated by third planet
- Troublesome configuration
KOI-268: Habitable zone?
- 1.7 Earth-radii, 110-day orbit, 295 K equilibrium
- Possibly a triple stellar system
- Only "habitable" if orbiting largest star
KOI-1845: Likely false positive
- Two candidates
- 2nd is 21 Earth radii, with V-shaped transit
- Faint stellar companion at large separation
- Likely a background eclipsing binary, not a planet
Statistics of Binaries
Are binary systems different?
Binarity vs. Temperature
Binarity vs. # of Candidates
Might indicate more false positives among single-candidate systems.
Binarity vs. Candidate Period
Short-period giant planets 2-3x more likely to reside in binary systems (98% confidence)
Robo-AO and Kepler
By Gregory Green