Recent & planned high-contrast work on the WCS and P3K Gene Serabyn Nov. 12, 2007

Strehl vs. wavelength Go short or go deep WCS provides P3K ExAO performance now HH AO ExAO,WCS ExAO On WCS

Well Corrected Subaperture (WCS) Relay Optics Magnify pupil Keep pupil location at DM Center sub-pupil on DM Maintain F# to AO system ROB AO

Potential ExAO Directions Programs: –Short wavelength/visible AO –Faint companion observations: Coronagraphy Transit observations Nulling Interferometry Make use of: –High Strehl –Stable PSF –Stable pointing (remove NCP drifts after AO) –Speckle reduction

ExAO Goals and Needs High StrehlStable Pointing Coronagraphic Masks Speckle reduction Short wavelength Imaging X Exoplanet transits XX Faint Companion Coronagraphy XXXX Nulling Interferometry* XX *Needs 2 good sub-apertures

(Bright) Companion Signal Levels: Brown Dwarfs & Hot Jupiters Thermal flux ratio = B pl A pl /(B * A * ) –(in RJ limit = T pl A pl /T * A * ) Area ratio  0.01 –(primary transits) Temp ratio  0.2 Flux ratio as much as a few 0.1% –(secondary transits, imaging) Transit observations: –Need photometric stability of order 0.1% Coronagraphic observations –Need small inner working angle (IWA), low wavefront rms –Need high contrast near IWA

Best Strehl ratio  rms  nm Strehl stability: 1 % rms Exoplanet Transit Spectroscopy: Strehl Stability

Exoplanet Transit Spectroscopy Stabilize ExAO PSF on slit Difference spectra before and during transits Non-common path pointing drift removal essential –new SSMs A handful of targets are bright enough with WCS H/K grism will help sensitivity 5 m collecting area will help increase target list

High-Strehl Coronagraphy FQPM coronagraphy Pupil plane phase coronagraphy (e.g. coma) Band-limited masks: linear mask good for binaries Need a good wavefront and a good coronagraph Goal is small inner working angle Can partially make up for smaller aperture

“Through–FQPM” image Peak extinction = 80 Mean of 5 short exposures (total time = 21.24s) Cross-diagonal subtraction Peak extinction = 235  6 mag Normal “off-FQPM” image High-contrast Coronagraphy: The Binary Star HD through a FQPM Focal plane phase masks (FQPM, vortex) allow small IWA

Brown Dwarf pair HD at K s Broadband: K s Stellar rejection  35:1  K s = 6.9 ± 0.5 separation = 2.61 ± 0.08“ At  7.5 /D Lyot  Could see it to 1.5 /D Lyot Looked at fainter, closer BDs 9/06 –now 50:1 K s Limitations: –Mask performance –SSM mirror actuator accuracy Need to stay on the crosshairs –Long-lived speckles 500:1 1.5 /D

Off-axis Performance “Off-FQPM” PSF “On-FQPM” PSF Quadrant-subtracted PSF The quadrant subtraction improves the rejection of the peak, but also the halo. Below at 2 /D Waiting to develop and install new masks Need to remove long-lived speckles

Pupil Phase Coronagraphy (Coma) I scat = (1-S)/N 2  4  Example: 1.4 waves PV of coma at 2.16  m Example of pupil phase coronagraphy (Codona et al.) Generate dark hole on half of image I scat Ideal 1 st ring

Pupil phase (coma) coronagraphy Initial trial carried out on the WCS in 9/06 Dark area at the 2 x level at  2 /D Saw very long-lived speckles Require non-common path error reduction/ long-lived speckle reduction Can move on to more complex phase distributions

Comparison of Coronagraphs Guyon et al. 2006

Visible AO in the B-band ( nm): 1 pix. = 25.3 mas /D (B) = 59 mas Strehl  0.10 – 0.12 SAO V = 4.5, 6.0 sep = 0.90 arcsec SAO V = 5.1, 6.3 sep = 0.34 arcsec Blue companions to red giants/supergiants Sirius, O Ceti, etc… –White dwarf/supergiant flux ratio  in the red –Much better blue ratio because WDs are very hot –Can move to fainter stars with P3K Red/Vis AO

Sensitivity Limitations to WCS Science camera sensitivity –Lose factor of ten for area –Lose small factor for transmission (t  0.8) through WCS relay –Gain small factor for Strehl improvement (1.5) –WCS roughly an order of magnitude less sensitive than 5 m aperture WFS sensitivity –Also lose first two factors for WFS –WFS cutoff roughly 3 magnitudes higher Flexcam sensitivity –Removes non-common path pointing drift –Not the best camera –Same issues as science camera Limit for the latter two systems is currently ~ 10 th mag –Limit not fundamental for flexcam

P3K Implications/Improvements WCS imaging performance for entire 5 m –Coronagraphs –Transits Science camera and “flexcam” sensitivities to improve by ~ 3 mag –Fainter sources –Disks as well as companion searches –Can also get better flexcam WFS sensitivity loss remains WFS another 2.5 mag worse with P3K+WCS Interesting for very high Strehl coronagraphy and high-Strehl vis AO (red and blue)

Science Goals High Strehl stability for transits (HJs) High contrast at small IWA for companion searches (BDs, etc.) High Strehl for short wavelength AO (WDs)

Prelminary Experiments with the WCS –Extreme AO PSF properties/stability in high-Strehl regime Non-common path error reduction (tip-tilt; higher order) Dark hole generation Atmospheric Characterisation Spatial filtered WFS –Visible AO Initial observations of close binaries Atmospheric properties (isoplanatic angle…) Laser guide star visible AO? –High-contrast IR coronagraphy (S > 90%) FQPM, Pupil-Phase, Band-limited, Vortex, apodized pupil, etc… Dark-hole, PSF subtraction, dual- imaging, dual-polarization imaging… –Palomar provides an excellent venue for new techniques –Preliminary experiments can accelerate P3K (new SSMs, SF WFS, speckle reduction…) and help keep the lead

Nulling Interferometry on the 200-inch with a rotating baseline Phase the two subapertures to center a dark interference fringe on a bright star Rotate pupil image or applied phase map to modulate off-axis signals Dual subaperture approach Signals from off-axis sources: Green = /2b Blue = 3 /2b 0 

Expected Performance without Phase Control Model 100 rotations: top envelope gives avg. null of 0.1 with current AO Measure bottom envelope shape rapidly ExAO will lower top envelope to 0.01 and make a huge difference Phase control between subapertures will also provide improvement