Laboratory and On-sky Validation of the Shaped Pupil Coronagraph’s Sensitivity to Low-order Aberrations With Active Wavefront Control

Abstract

We present early laboratory simulations and extensive on-sky tests validating of the performance of a shaped pupil coronagraph (SPC) behind an extreme-AO corrected beam of the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system. In tests with the SCExAO internal source/wavefront error simulator, the normalized intensity profile for the SPC degrades more slowly than for the Lyot coronagraph as low-order aberrations reduce the Strehl ratio from extremely high values (S.R. ∼ 0.93-0.99) to those characteristic of current ground-based extreme AO systems (S.R. ∼ 0.74-0.93) and then slightly lower values down to S.R. ∼ 0.57. On-sky SCExAO data taken with the SPC and other coronagraphs for brown dwarf/planet-hosting stars HD 1160 and HR 8799 provide further evidence for the SPC's robustness to low-order aberrations. From H-band Strehl ratios of 80% to 70%, the Lyot coronagraph's performance vs. that of the SPC may degrade even faster on sky than is seen in our internal source simulations. The 5-σ contrast also degrades faster (by a factor of two) for the Lyot than the SPC. The SPC we use was designed as a technology demonstrator only, with a contrast floor, throughput, and outer working angle poorly matched for SCExAO's current AO performance and poorly tuned for imaging the HR 8799 planets. Nevertheless, we detect HR 8799 cde with SCExAO/CHARIS using the SPC in broadband mode, where the S/N for planet e is within 30% of that obtained using the vortex coronagraph. The shaped-pupil coronagraph is a promising design demonstrated to be robust in the presence of low-order aberrations and may be well-suited for future ground and space-based direct imaging observations, especially those focused on follow-up exoplanet characterization and technology demonstration of deep contrast within well-defined regions of the image plane.

SCExAO/CHARIS Near-IR High-contrast Imaging and Integral Field Spectroscopy of the HIP 79977 Debris Disk

“…2-0. 75 later estimated from spectrophotometrically calibrated data were characteristic of those obtained with H-band Strehls of 70-80% (Currie et al 2018a).…”

SCExAO/MEC and CHARIS Discovery of a Low-mass, 6 au Separation Companion to HIP 109427 Using Stochastic Speckle Discrimination and High-contrast Spectroscopy*

“…As with the CHARIS data, satellite spots were used for the spectrophotometric calibration reference. We adopted the scaling between modulation amplitude and contrast from Currie et al (2018b) to generate the expected satellite spot flux values per passband. A stellar spectrum from the PHOENIX stellar library appropriate for an A1V star was used and the data normalized to match HIP 109427ʼs reported J band flux (Ducati 2002).…”

SCExAO/CHARIS Near-infrared Direct Imaging, Spectroscopy, and Forward-Modeling of κ And b: A Likely Young, Low-gravity Superjovian Companion

“…The JHK data for HD 1160 from SCExAO/CHARIS data for HD 1160 were previously reported in Currie et al (2018), taken on 6 September 2017 in two sequences, one with the Lyot coronagraph and another using the shaped-pupil coronagraph with good AO performance. HD 1160 B is detected at a high significance in both data sets in all individual channels and data cubes, even without PSF subtraction techniques applied (SNR ∼ 100 in the wavelength-collapsed, sequence combined image).…”