Early High-contrast Imaging Results with Keck/NIRC2-PWFS: The SR 21 Disk

Abstract

High-contrast imaging of exoplanets and protoplanetary disks depends on wavefront sensing and correction made by adaptive optics instruments. Classically, wavefront sensing has been conducted at optical wavelengths, which made high-contrast imaging of red targets such as M-type stars or extincted T Tauri stars challenging. Keck/NIRC2 has combined near-infrared (NIR) detector technology with the pyramid wavefront sensor (PWFS). With this new module we observed SR~21, a young star that is brighter at NIR wavelengths than at optical wavelengths. Compared with the archival data of SR~21 taken with the optical wavefront sensing we achieved $\sim$20\% better Strehl ratio in similar natural seeing conditions. Further post-processing utilizing angular differential imaging and reference-star differential imaging confirmed the spiral feature reported by the VLT/SPHERE polarimetric observation, which is the first detection of the SR~21 spiral in total intensity at $L^{\prime }$ band. We also compared the contrast limit of our result ($10^{-4}$ at $0\farcs4$ and $2\times 10^{-5}$ at $1\farcs0$) with the archival data that were taken with optical wavefront sensing and confirmed the improvement, particularly at $\leq0\farcs5$. Our observation demonstrates that the NIR PWFS improves AO performance and will provide more opportunities for red targets in the future.

accepted for publication in AJ, 8 pages, 7 figures

References in corpus (13)

• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• A Spitzer Survey of Young Stellar Clusters within One Kiloparsec of the Sun: Cluster Core Extraction and Basic Structural Analysis
• An Optical Spectroscopic Study of T Tauri Stars. I. Photospheric Properties
• The unWISE Catalog: Two Billion Infrared Sources from Five Years of WISE Imaging
• Accreting Circumplanetary Disks: Observational Signatures
• The Disk Substructures at High Angular Resolution Project (DSHARP): III. Spiral Structures in the Millimeter Continuum of the Elias 27, IM Lup, and WaOph 6 Disks
• The polarimetric imaging mode of VLT/SPHERE/IRDIS II: Characterization and correction of instrumental polarization effects
• Keck/NIRC2 $L$'-Band Imaging of Jovian-Mass Accreting Protoplanets around PDS 70
• Reference star differential imaging of close-in companions and circumstellar disks with the NIRC2 vortex coronagraph at W.M. Keck Observatory
• The W. M. Keck Observatory infrared vortex coronagraph and a first image of HIP79124 B
• Characterization of the inner disk around HD 141569 A from Keck/NIRC2 L-band vortex coronagraphy
• Near-Infrared Imaging of a Spiral in the CQ Tau Disk
• Combining angular differential imaging and accurate polarimetry with SPHERE/IRDIS to characterize young giant exoplanets

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• Direct Imaging Explorations for Companions around Mid-Late M Stars from the Subaru/IRD Strategic Program