Review of high-contrast imaging systems for current and future ground-based and space-based telescopes: Part II. Common path wavefront sensing/control and coherent differential imaging

The Optimal Optical Coronagraph (OOC) Workshop held at the Lorentz Center in September 2017 in Leiden, the Netherlands, gathered a diverse group of 25 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas. In this second installment of a series of three papers summarizing the outcomes of the OOC workshop, we present an overview of common path wavefront sensing/control and Coherent Differential Imaging techniques, highlight the latest results, and expose their relative strengths and weaknesses. We layout critical milestones for the field with the aim of enhancing future ground/space based high contrast imaging platforms. Techniques like these will help to bridge the daunting contrast gap required to image a terrestrial planet in the zone where it can retain liquid water, in reflected light around a G type star from space

Review of high-contrast imaging systems for current and future ground-based and space-based telescopes III: technology opportunities and pathways

The Optimal Optical CoronagraphWorkshop at the Lorentz Center in September 2017 in Leiden, the Netherlands gathered a diverse group of 30 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas. This contribution is the final part of a series of three papers summarizing the outcomes of the workshop, and presents an overview of novel optical technologies and systems that are implemented or considered for high-contrast imaging instruments on both ground-based and space telescopes. The overall objective of high contrast instruments is to provide direct observations and characterizations of exoplanets at contrast levels as extreme as 10^(-10). We list shortcomings of current technologies, and identify opportunities and development paths for new technologies that enable quantum leaps in performance. Specifically, we discuss the design and manufacturing of key components like advanced deformable mirrors and coronagraphic optics, and their amalgamation in "adaptive coronagraph" systems. Moreover, we discuss highly integrated system designs that combine contrast-enhancing techniques and characterization techniques (like high-resolution spectroscopy) while minimizing the overall complexity. Finally, we explore extreme implementations using all-photonics solutions for ground-based telescopes and dedicated huge apertures for space telescopes

Simultaneous exoplanet detection and instrument aberration retrieval in multispectral coronagraphic imaging

High-contrast imaging for the detection and characterization of exoplanets relies on the instrument's capability to block out the light of the host star. Some current post-processing methods for calibrating out the residual speckles use information redundancy offered by multispectral imaging but do not use any prior information on the origin of these speckles. We investigate whether additional information on the system and image formation process can be used to more finely exploit the multispectral information. We developed an inversion method in a Bayesian framework that is based on an analytical imaging model to estimate both the speckles and the object map. The model links the instrumental aberrations to the speckle pattern in the image focal plane, distinguishing between aberrations upstream and downstream of the coronagraph. We propose and validate several numerical techniques to handle the difficult minimization problems of phase retrieval and achieve a contrast of 10^6 at 0.2 arcsec from simulated images, in the presence of photon noise. This opens up the the possibility of tests on real data where the ultimate performance may override the current techniques if the instrument has good and stable coronagraphic imaging quality. This paves the way for new astrophysical exploitations or even new designs for future instruments

An Exo-Kuiper Belt with an Extended Halo around HD 191089 in Scattered Light

We have obtained Hubble Space Telescope STIS and NICMOS and Gemini/GPI scattered-light images of the HD 191089 debris disk. We identify two spatial components: a ring resembling the Kuiper Belt in radial extent (FWHM ~ 25 au, centered at ~46 au) and a halo extending to ~640 au. We find that the halo is significantly bluer than the ring, consistent with the scenario that the ring serves as the "birth ring" for the smaller dust in the halo. We measure the scattering phase functions in the 30°–150° scattering-angle range and find that the halo dust is more forward- and backward-scattering than the ring dust. We measure a surface density power-law index of −0.68 ± 0.04 for the halo, which indicates the slowdown of the radial outward motion of the dust. Using radiative transfer modeling, we attempt to simultaneously reproduce the (visible) total and (near-infrared) polarized intensity images of the birth ring. Our modeling leads to mutually inconsistent results, indicating that more complex models, such as the inclusion of more realistic aggregate particles, are needed

A White Paper Submitted to The National Academy of Science's Committee on Exoplanet Science Strategy: Observing Exoplanets with the James Webb Space Telescope

The James Webb Space Telescope (JWST) will revolutionize our understanding of exoplanets with transit spectroscopy of a wide range of mature planets close to their host stars (10 AU). The census of exoplanets has revealed an enormous variety of planets orbiting stars of all ages and spectral types. With TESS adding to this census with its all-sky survey of the closest, brightest stars, the challenge of the coming decade will be to move from demography to physical characterization. This white paper discusses the wide variety of exoplanet opportunities enabled by JWST's sensitivity and stability, its high angular resolution, and its suite of powerful instruments. JWST observations will advance our understanding of the atmospheres of young to mature planets and will provide new insights into planet formation

Review of high-contrast imaging systems for current and future ground-based and space-based telescopes: Part II. Common path wavefront sensing/control and coherent differential imaging

The Optimal Optical Coronagraph (OOC) Workshop held at the Lorentz Center in September 2017 in Leiden, the Netherlands, gathered a diverse group of 25 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas. In this second installment of a series of three papers summarizing the outcomes of the OOC workshop, we present an overview of common path wavefront sensing/control and Coherent Differential Imaging techniques, highlight the latest results, and expose their relative strengths and weaknesses. We layout critical milestones for the field with the aim of enhancing future ground/space based high contrast imaging platforms. Techniques like these will help to bridge the daunting contrast gap required to image a terrestrial planet in the zone where it can retain liquid water, in reflected light around a G type star from space

A White Paper Submitted to The National Academy of Science's Committee on Exoplanet Science Strategy: Observing Exoplanets with the James Webb Space Telescope

The James Webb Space Telescope (JWST) will revolutionize our understanding of exoplanets with transit spectroscopy of a wide range of mature planets close to their host stars (10 AU). The census of exoplanets has revealed an enormous variety of planets orbiting stars of all ages and spectral types. With TESS adding to this census with its all-sky survey of the closest, brightest stars, the challenge of the coming decade will be to move from demography to physical characterization. This white paper discusses the wide variety of exoplanet opportunities enabled by JWST's sensitivity and stability, its high angular resolution, and its suite of powerful instruments. JWST observations will advance our understanding of the atmospheres of young to mature planets and will provide new insights into planet formation

An Exo-Kuiper Belt with an Extended Halo around HD 191089 in Scattered Light

We have obtained Hubble Space Telescope STIS and NICMOS and Gemini/GPI scattered-light images of the HD 191089 debris disk. We identify two spatial components: a ring resembling the Kuiper Belt in radial extent (FWHM ~ 25 au, centered at ~46 au) and a halo extending to ~640 au. We find that the halo is significantly bluer than the ring, consistent with the scenario that the ring serves as the "birth ring" for the smaller dust in the halo. We measure the scattering phase functions in the 30°–150° scattering-angle range and find that the halo dust is more forward- and backward-scattering than the ring dust. We measure a surface density power-law index of −0.68 ± 0.04 for the halo, which indicates the slowdown of the radial outward motion of the dust. Using radiative transfer modeling, we attempt to simultaneously reproduce the (visible) total and (near-infrared) polarized intensity images of the birth ring. Our modeling leads to mutually inconsistent results, indicating that more complex models, such as the inclusion of more realistic aggregate particles, are needed

A deep search for planets in the inner 15 au around Vega

We present the results of a deep high-contrast imaging search for planets around Vega. Vega is an ideal target for high-contrast imaging because it is bright, nearby, and young with a face-on two-belt debris disk which may be shaped by unseen planets. We obtained $J-$ and $H-$band data on Vega with the coronagraphic integral-field spectrograph Project 1640 (P1640) at Palomar Observatory. Two nights of data were obtained in 2016, in poor seeing conditions, and two additional nights in more favorable conditions in 2017. In total, we obtained 5.5 hours of integration time on Vega in moderate to good seeing conditions (<1.5"). We did not detect any low mass companions in this system. Our data present the most sensitive contrast limits around Vega at very small separations (2-15 au) thus far, allowing us to place new constraints on the companions which may be sculpting the Vega system. In addition to new constraints, as the deepest data obtained with P1640, these observations form the final legacy of the now decommissioned instrument.Comment: Accepted for publication in A