Adaptive Optics Imaging Research Articles

A possibly inflated planet around the bright young star DS Tucanae A

Context. The origin of the observed diversity of planetary system architectures is one of the main topics of exoplanetary research. The detection of a statistically significant sample of planets around young stars allows us to study the early stages of planet formation and evolution, but only a handful are known so far. In this regard a considerable contribution is expected from the NASA TESS satellite, which is now performing a survey of ~85% of the sky to search for short-period transiting planets. Aims. In its first month of operation TESS found a planet candidate with an orbital period of 8.14 days around a member of the Tuc-Hor young association (~40 Myr), the G6V main component of the binary system DS Tuc. If confirmed, it would be the first transiting planet around a young star suitable for radial velocity and/or atmospheric characterisation. Our aim is to validate the planetary nature of this companion and to measure its orbital and physical parameters. Methods. We obtained accurate planet parameters by coupling an independent reprocessing of the TESS light curve with improved stellar parameters and the dilution caused by the binary companion; we analysed high-precision archival radial velocities to impose an upper limit of about 0.1 MJup on the planet mass; we finally ruled out the presence of external companions beyond 40 au with adaptive optics images. Results. We confirm the presence of a young giant (R = 0.50 RJup) planet having a non-negligible possibility to be inflated (theoretical mass ≲ 20 M⊕) around DS Tuc A. We discuss the feasibility of mass determination, Rossiter-McLaughlin analysis, and atmosphere characterisation allowed by the brightness of the star.

Space targets adaptive optics images blind restoration by convolutional neural network

To obtain sharp images of space targets, high-accuracy restoration of degraded images corrected by an adaptive optics (AO) system is necessary. Existing algorithms are mainly based on the physical constraints of both image and point-spread function (PSF), which are usually continuously estimated in an alternately iterative manner and take a long time to restore blurred images. We propose an end-to-end blind restoration method for ground-based space target images based on conditional generative adversarial network without estimating PSF. The whole network consists of two parts, generator network and discriminator network, which are used for learning the atmospheric degradation process and achieving the purpose of generating restored images. To train the network, a simulated AO image dataset containing 4800 sharp–blur image pairs is constructed by 80 three-dimensional models of space targets combined with degradation of atmospheric turbulence. Experimental results demonstrate that the proposed method not only enhances the restoration accuracy but also improves the restoration efficiency of single-frame object images.

A SHARP view of H0LiCOW: H0 from three time-delay gravitational lens systems with adaptive optics imaging

ABSTRACTWe present the measurement of the Hubble constant, H0, with three strong gravitational lens systems. We describe a blind analysis of both PG 1115+080 and HE 0435−1223 as well as an extension of our previous analysis of RXJ 1131−1231. For each lens, we combine new adaptive optics (AO) imaging from the Keck Telescope, obtained as part of the SHARP (Strong-lensing High Angular Resolution Programme) AO effort, with Hubble Space Telescope (HST) imaging, velocity dispersion measurements, and a description of the line-of-sight mass distribution to build an accurate and precise lens mass model. This mass model is then combined with the COSMOGRAIL-measured time delays in these systems to determine H0. We do both an AO-only and an AO + HST analysis of the systems and find that AO and HST results are consistent. After unblinding, the AO-only analysis gives $H_{0}=82.8^{+9.4}_{-8.3}~\rm km\, s^{-1}\, Mpc^{-1}$ for PG 1115+080, $H_{0}=70.1^{+5.3}_{-4.5}~\rm km\, s^{-1}\, Mpc^{-1}$ for HE 0435−1223, and $H_{0}=77.0^{+4.0}_{-4.6}~\rm km\, s^{-1}\, Mpc^{-1}$ for RXJ 1131−1231. The joint AO-only result for the three lenses is $H_{0}=75.6^{+3.2}_{-3.3}~\rm km\, s^{-1}\, Mpc^{-1}$. The joint result of the AO + HST analysis for the three lenses is $H_{0}=76.8^{+2.6}_{-2.6}~\rm km\, s^{-1}\, Mpc^{-1}$. All of these results assume a flat Λ cold dark matter cosmology with a uniform prior on Ωm in [0.05, 0.5] and H0 in [0, 150] $\rm km\, s^{-1}\, Mpc^{-1}$. This work is a collaboration of the SHARP and H0LiCOW teams, and shows that AO data can be used as the high-resolution imaging component in lens-based measurements of H0. The full time-delay cosmography results from a total of six strongly lensed systems are presented in a companion paper.

High-Resolution, Adaptive Optics Imaging of the Human Trabecular Meshwork In Vivo.

PurposeTo image the human trabecular meshwork (TM) in vivo using adaptive optics gonioscopy (AOG) with approximately 2-μm lateral resolution.MethodsAn existing Indiana University adaptive optics scanning laser ophthalmoscope was altered by adding a 12-mm button lens to a clinical gonioscopic lens allowing high-resolution imaging of the human iridocorneal angle. First an anatomic model eye was used to refine the imaging technique and then nine participants (7 controls and 2 participants with pigment dispersion syndrome) were imaged.ResultsAll nine participants were successfully imaged without adverse events. High-resolution imaging of the human TM was achieved allowing for visualization of the TM beams, and presumed endothelial cells. Uveal meshwork beams in controls averaged 25.5 μm (range, 15.2–44.7) in diameter with pores averaging 42.6 μm (range, 22.3–51.4) while the corneoscleral meshwork pores averaged 8.9 μm (range, 7.7–12.1). Differences in appearance of the uveal and corneoscleral meshwork were noted between the two participants with pigment dispersion syndrome and the controls. These included nearly absent spacing between the beams and enlarged endothelial cells with hyperreflective areas.ConclusionsAOG allows for near cellular level resolution of the human TM in vivo. This may allow for further understanding of age-related changes that occur as well as provide a deeper understanding of medical and surgical alterations for the treatment of glaucoma.Translational RelevanceFurther development of this approach may allow for direct measurements at a micometer level in vivo of changes that occur in the human trabecular meshwork with glaucoma and therapeutic interventions.

A Catastrophic Failure to Build a Massive Galaxy around a Supermassive Black Hole at z = 3.84

Abstract We present observations of the stellar and molecular gas mass of SDSS J163909+282447.1, a luminous quasar at z = 3.84 with an extreme mass for a supermassive black hole (SMBH; M BH = 2.5 × 1010 M ⊙). The local SMBH mass–galaxy mass relation predicts a massive host galaxy with M stellar ≳ 1012 M ⊙ for this quasar. Based on sensitive near-infrared imaging with adaptive optics (AO) using Subaru, the stellar light from the host is undetected, thus resulting in an upper limit on the mass, M stellar < 6.3 × 1010 M ⊙, a factor of ≳16 less than expected. The CO(4 − 3) observations at 0.″2 resolution using the Atacama Large Millimeter/submillimeter Array indicate a molecular gas mass from CO of M ⊙ and a dynamical mass within a radius of 0.45 ± 0.2 kpc of M ⊙. With the SMBH accounting for ∼60% of the dynamical mass and considering the amount of molecular gas, we find an upper limit on the stellar mass to be M stellar ≲ 1.5 × 1010 M ⊙, a value consistent with the limit from Subaru AO imaging. Based on these results, this SMBH has one of the largest host stellar mass deficits known given its SMBH mass; hence, it is unclear how to grow a SMBH/host galaxy to such a state since there is not enough molecular gas available to form a substantial amount of stellar mass to make up for the difference. Any physical model is likely to require an earlier phase of super-Eddington accretion onto the SMBH.

3C 294 revisited: Deep Large Binocular Telescope AO NIR images and optical spectroscopy

Context. High redshift radio galaxies are among the most massive galaxies at their redshift, are often found at the center of protoclusters of galaxies, and are expected to evolve into the present day massive central cluster galaxies. Thus they are a useful tool to explore structure formation in the young Universe. Aims. 3C 294 is a powerful FR II type radio galaxy at z = 1.786. Past studies have identified a clumpy structure, possibly indicative of a merging system, as well as tentative evidence that 3C 294 hosts a dual active galactic nucleus (AGN). Due to its proximity to a bright star, it has been subject to various adaptive optics imaging studies. Methods. In order to distinguish between the various scenarios for 3C 294, we performed deep, high-resolution adaptive optics near-infrared imaging and optical spectroscopy of 3C 294 with the Large Binocular Telescope. Results. We resolve the 3C 294 system into three distinct components separated by a few tenths of an arcsecond on our images. One is compact, the other two are extended, and all appear to be non-stellar. The nature of each component is unclear. The two extended components could be a galaxy with an internal absorption feature, a galaxy merger, or two galaxies at different redshifts. We can now uniquely associate the radio source of 3C 294 with one of the extended components. Based on our spectroscopy, we determined a redshift of z = 1.784 ± 0.001, which is similar to the one previously cited. In addition we found a previously unreported emission line at λ6749.4 Å in our spectra. It is not clear that it originates from 3C 294. It could be the Ne [IV] doublet λ2424/2426 Å at z = 1.783, or belong to the compact component at a redshift of z ∼ 4.56. We thus cannot unambiguously determine whether 3C 294 hosts a dual AGN or a projected pair of AGNs.

TESS Hunt for Young and Maturing Exoplanets (THYME): A Planet in the 45 Myr Tucana–Horologium Association

Abstract Young exoplanets are snapshots of the planetary evolution process. Planets that orbit stars in young associations are particularly important because the age of the planetary system is well constrained. We present the discovery of a transiting planet larger than Neptune but smaller than Saturn in the 45 Myr Tucana–Horologium young moving group. The host star is a visual binary, and our follow-up observations demonstrate that the planet orbits the G6V primary component, DS Tuc A (HD 222259A, TIC 410214986). We first identified transits using photometry from the Transiting Exoplanet Survey Satellite (TESS; alerted as TOI 200.01). We validated the planet and improved the stellar parameters using a suite of new and archival data, including spectra from Southern Astrophysical Research/Goodman, South African Extremely Large Telescope/High Resolution Spectrograph and Las Cumbres Observatories/Network of Robotic Echelle Spectrographs; transit photometry from Spitzer; and deep adaptive optics imaging from Gemini/Gemini Planet Imager. No additional stellar or planetary signals are seen in the data. We measured the planetary parameters by simultaneously modeling the photometry with a transit model and a Gaussian process to account for stellar variability. We determined that the planetary radius is 5.70 ± 0.17 R ⊕ and that the orbital period is 8.1 days. The inclination angles of the host star’s spin axis, the planet’s orbital axis, and the visual binary’s orbital axis are aligned within 15° to within the uncertainties of the relevant data. DS Tuc Ab is bright enough (V = 8.5) for detailed characterization using radial velocities and transmission spectroscopy.

A Hot Saturn Near (but Unassociated with) the Open Cluster NGC 1817

Abstract We report on the discovery of a hot Saturn-sized planet (9.916 ± 0.985 R ⊕) around a late F-star, K2-308, observed in Campaign 13 of the K2 mission. We began studying this planet candidate because prior to the release of Gaia DR2, the host star was thought to have been a member ( membership probability) of the open cluster NGC 1817 based on its kinematics and photometric distance. We identify the host star (among three stars within the K2 photometric aperture) using seeing-limited photometry and rule out false-positive scenarios using adaptive optics imaging and radial velocity observations. We statistically validate K2-308b by calculating a false-positive probability rate of . However, we also show using new kinematic measurements provided by Gaia DR2 and our measured radial velocity of the system that K2-308 is unassociated with the cluster NGC 1817. Therefore, the long running search for a giant transiting planet in an open cluster remains fruitless. Finally, we note that our use of seeing-limited photometry is a good demonstration of similar techniques that are already being used to follow up Transiting Exoplanet Survey Satellite (TESS) planet candidates, especially in crowded regions.

Adaptive Optics Images in Clinical Trials of Retinal Disease

Adaptive Optics Images in Clinical Trials of Retinal Disease

Photoreceptor Degeneration is Correlated With the Deterioration of Macular Retinal Sensitivity in High Myopia

To investigate structural changes in the retinal outer layers and choroid using adaptive optics (AO) and optical coherence tomography (OCT) in eyes with myopia, and to correlate the changes with decreased macular light sensitivity (MLS). This prospective study included 27 subjects with emmetropia and low myopia (EM/LM), 25 with moderate myopia (MM), and 25 with high myopia (HM). Microperimetry was used to quantify MLS in each subject, while AO and OCT images of fundus were analyzed to quantify cone density and regularity and thickness of outer retinal sublayers and choroid. Differences of MLS, cone distribution, and chorioretinal thicknesses were compared among the three groups, and the associations among photoreceptor morphological alterations, MLS, and other parameters were analyzed. In HM, the MLS, cone density and regularity, and thicknesses of the myoid and ellipsoid zone (MEZ), Henle fiber layer and outer nuclear layer, interdigitation zone and RPE/Bruch complex, and choroid were lower than in EM/LM. Decreased MLS was correlated with lower cone density and regularity, and thinner MEZ and choroid in the inner region, and with lower cone density, thinner MEZ and choroid, and longer axial length in the outer region. Multivariate regression showed that better MLS was correlated with thicker MEZ in the inner region and with higher cone density in the outer region. Altered cone distribution and outer retinal thickness, especially cone density and MEZ thickness, were significantly correlated with decline of MLS in HM, which may help to evaluate and monitor visual impairment in HM.

Identifying optical turbulence profiles for realistic tomographic error in adaptive optics

ABSTRACT For extremely large telescopes, adaptive optics will be required to correct the Earth’s turbulent atmosphere. The performance of tomographic adaptive optics is strongly dependent on the vertical distribution (profile) of this turbulence. An important way in which this manifests is the tomographic error, arising from imperfect measurement and reconstruction of the turbulent phase at altitude. Conventionally, a small number of reference profiles are used to obtain this error in simulation; however these profiles are not constructed to be representative in terms of tomographic error. It is therefore unknown whether these simulations are providing realistic performance estimates. Here, we employ analytical adaptive optics simulation that drastically reduces computation times to compute tomographic error for 10 691 measurements of the turbulence profile gathered by the Stereo-SCIDAR instrument at ESO Paranal. We assess for the first time the impact of the profile on tomographic error in a statistical manner. We find, in agreement with previous work, that the tomographic error is most directly linked with the distribution of turbulence into discrete, stratified layers. Reference profiles are found to provide mostly higher tomographic error than expected, which we attribute to the fact that these profiles are primarily composed of averages of many measurements resulting in unrealistic, continuous distributions of turbulence. We propose that a representative profile should be defined with respect to a particular system, and that as such simulations with a large statistical sample of profiles must be an important step in the design process.

The association between cone density and visual function in the macula of patients with retinitis pigmentosa.

We observed cone photoreceptors by using adaptive optics (AO) fundus camera and optical coherence tomography (OCT) in patients with retinitis pigmentosa (RP) and examined the correlations between cone photoreceptors and visual function over 2years. Six patients with RP were studied. All patients underwent measurement using best-corrected decimal visual acuity, OCT, a Humphrey Field Analyzer with the 10-2 test grid pattern, and AO. AO images of the foveal center were obtained using an rtx1™ AO fundus camera, and cone counting was performed at 0.5mm from the foveal center. AO detected a decrease of cone density over 2years in RP patients. However, visual acuity, foveal sensitivity, and photoreceptor thickness were not changed over the 2years. AO images showed a decrease in the number of foveal cone densities over 2years in patients with RP. AO may shorten the period required to predict the RP progression rate.

Imaging single-cell blood flow in the smallest to largest vessels in the living retina.

Tissue light scatter limits the visualization of the microvascular network deep inside the living mammal. The transparency of the mammalian eye provides a noninvasive view of the microvessels of the retina, a part of the central nervous system. Despite its clarity, imperfections in the optics of the eye blur microscopic retinal capillaries, and single blood cells flowing within. This limits early evaluation of microvascular diseases that originate in capillaries. To break this barrier, we use 15 kHz adaptive optics imaging to noninvasively measure single-cell blood flow, in one of the most widely used research animals: the C57BL/6J mouse. Measured flow ranged four orders of magnitude (0.0002-1.55 µL min-1) across the full spectrum of retinal vessel diameters (3.2-45.8 µm), without requiring surgery or contrast dye. Here, we describe the ultrafast imaging, analysis pipeline and automated measurement of millions of blood cell speeds.

Repeatability of Adaptive Optics Automated Cone Measurements in Subjects With Retinitis Pigmentosa and Novel Metrics for Assessment of Image Quality.

PurposeWe determine the intersession repeatability of cone measurements via flood-illuminated adaptive optics (AO) imaging in patients with retinitis pigmentosa (RP), to better differentiate variation due to imaging inaccuracies versus pathology-driven change.MethodsA total of 25 4° × 4° AO images were acquired three times on the same day in 10 subjects with RP, registered in i2K Retina, and cones were identified using a custom-built MATLAB algorithm. Nine equally spaced regions of interest were selected for each imaging set. A subset of subjectively “poor” and “good” quality images was selected by three independent graders, analyzed using cone density, cone location similarity (CLS) and cone spacing, and compared to age-matched normals.ResultsThe coefficient of variation (CoV), repeatability, and percent repeatability of automated cone density were slightly higher in patients with RP compared to age-matched normals, but showed no statistically significant difference. The standard deviation of CLS and cone spacing of nearest-neighbor distance demonstrated a statistically significant difference between good- and poor-quality images.ConclusionsRepeatability of automated cone density measurements in patients with RP is comparable to normals. Misidentification of cones due to image quality variability is a major limitation of automated cone counting algorithms in patients with RP. Our study suggests that CLS and cone spacing metrics could be used to help define image quality and, thus, increase confidence in automated cone counts in patients with RP.Translational RelevanceThe novel AO image quality assessment metrics described in our study could help to improve patient image interpretation, prognosis, and longitudinal care.

Visual Function at the Atrophic Border in Choroideremia Assessed with Adaptive Optics Microperimetry

Recent advances in retinal imaging allow visualization of structural abnormalities in retinal disease at the cellular level. This study used adaptive optics (AO) microperimetry to assess visual sensitivity with high spatial precision and to examine how function varies across 2 phenotypic features observed in choroideremia: atrophic lesion borders and outer retinal tubulations (ORTs). Cross-sectional study. Twelve choroideremia patients. A custom AO scanning light ophthalmoscope (AOSLO) equipped with both confocal and nonconfocalsplit-detection imaging methods was used to image the photoreceptor inner and outer segment mosaics. For AO microperimetry, circular 550-nm stimuli were presented through the AOSLO system; stimuli were either 9.6 or 38.3 arcmin2 (approximately 60 or 15 times smaller than a Goldman III stimulus). Test locations were identified in structural images and stimuli were targeted to these locations using real-time retinal tracking combined with measurements of transverse chromatic aberration. Psychophysical detection thresholds were measured at the atrophic border in 12 patients. Additionally, visual sensitivity was probed along ORTs in 4patients. Visual sensitivity thresholds measured with AO microperimetry at retinal locations corresponding to structural phenotypes observed on AOSLO retinal images. In choroideremia, sharp borders between intact central islands of the photoreceptor mosaic and complete atrophy of the outer retina and retinal pigment epithelium were observed in both split-detection and confocal structural images. Adaptive optics microperimetry at locations spanning these borders showed a commensurately sharp decrease in function, with readily measurable visual sensitivity on one side and dense scotoma on the other. These functional transitions often occurred over a distance smaller than the diameter of the Goldman III stimulus. Thresholds measured along ORTs showed dense scotoma over the tubule in all 4 participants, despite the visibility of remnant cone inner segments on the AO images. Choroideremia patients exhibited sharp functional transitions that collocated with structural transitions from intact to severely degenerated retina. We found no evidence of visual sensitivity over ORTs. Measuring cone function with high resolution offered insight into disease mechanisms and may enable precise assessment of whether experimental therapies, such as gene therapy, provide a functional benefit.

Long-term changes of retinal pigment epithelium in the eyes with Vogt-Koyanagi-Harada disease observed by adaptive optics imaging.

Purpose: To observe long-term changes of the retinal pigment epithelium (RPE) in the eyes of patients with Vogt-Koyanagi-Harada (VKH) disease using an adaptive optics (AO) fundus camera, and their correlation with the findings of spectral-domain optical coherence tomography (SD-OCT), fundus autofluorescence (AF) imaging.Patients and methods: Three eyes of two patients with new-onset acute VKH disease were retrospectively studied. After the serous retinal detachment was resolved by high-dose corticosteroid treatment, the patients were examined with SD-OCT, blue-wavelength AF, near-infrared (NIR) AF, and an AO fundus camera. AO images of the macula were obtained using the rtx1TM AO fundus camera. The area around the foveal center of the hyper-reflective lesion in AO imaging was measured manually. The time at which the serous retinal detachment resolved was set as the baseline, and AO and other images were obtained every 3 to 6 months from the baseline.Results: In all three eyes, lesions with elevation or thickening of the RPE layer were observed with OCT imaging in the macula after the serous retinal detachment resolved. These lesions showed hyper-autofluorescence in NIR-AF image and hyper-reflective lesions with clear boundaries in AO image. The area of the hyper-reflective lesions of AO images in each eye showed an approximately 40% decrease at 6 months from baseline. However, the hyper-reflective lesion remained to some extent after 18 months in case 1 and 36 months in case 2.Conclusions: By using OCT, fundus autofluorescence and AO images, it was possible to observe temporal changes of RPE layer in VKH eyes noninvasively. High-resolution AO images also allow us to observe for improvements in the elevation or thickening of the RPE layer quantitatively.

Evaluation of Transplanted Autologous Induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium in Exudative Age-Related Macular Degeneration

To report the results after 4 years of follow-up in a previously presented first case of induced pluripotent stem cell (iPSC)-derived retinal pigment epithelium (RPE) sheet autologous transplantation using multimodal imaging. Follow-up of a single case. A patient with exudative age-related macular degeneration and polypoidal choroidal vasculopathy. Transplantation of an autologous iPSC-derived RPE cell sheet after removal of choroidal neovascularization (CNV) in September2014. The function of the graft was assessed 4 years after surgery by color fundus photography, spectral-domain (SD) OCT, fluorescein angiography, indocyanine green angiography, and an adaptive optics (AO) retinal camera. At the 4-year follow-up, the transplanted autologous iPSC-derived RPE sheet had survived beneath the retina with slight expansion of the pigmented area and no adverse events. The outer nuclear layer above and adjacent to the graft showed acceptable thickness and an organized structure. Fluorescein angiography and SD OCT suggested the presence of vessel-like structures confined to the grafted area associated with the remaining trunk vessel of preoperative polypoidal choroidal vasculopathy but with no exudative changes. Visual acuity has been stable with no additional injections of anti-vascular endothelial growth factor agent. The choroidal volume at the graft site is relatively preserved when compared with the volume outside this site without RPE after removal of the CNV. Indocyanine green angiography revealed a preserved choriocapillaris around the iPSC-derived RPE sheet. Dark cell-like structures with a predominantly hexagonal arrangement were observed by AO imaging in an area located near the margin of the graft sheet. The average intercell distance was found to be stable over time. Thus far, the grafted iPSC-derived RPE sheet has survived for 4 years and seems to support photoreceptors and choroidal vessels. The morphologic characteristics of the RPE are observed at the transplant site.

Tiny grains shining bright in the gaps of Herbig Ae transitional discs

ABSTRACT This work presents a study of two Herbig Ae transitional discs, Oph IRS 48 and HD 169142; which both have reported rings in their dust density distributions. We use Keck-II/NIRC2 adaptive optics imaging observations in the L′ filter (3.8 $\mu$m) to probe the regions of these discs inwards of ${\sim }20\, \mathrm{au}$ from the star. We introduce our method for investigating these transitional discs, which takes a forward modelling approach: making a model of the disc (using the Monte Carlo radiative transfer code radmc3d), convolving it with point spread functions of calibrator stars, and comparing the convolved models with the observational data. The disc surface density parameters are explored with a Monte Carlo Markov Chain technique. Our analysis recovers emission from both of the discs interior to the well-known optically thick walls, modelled as a ring of emission at ${\sim }15\, \mathrm{au}$ in Oph IRS 48, and ${\sim }7\, \mathrm{au}$ for HD 169142, and identifies asymmetries in both discs. Given the brightness of the near-symmetric rings compared to the reported companion candidates, we suggest that the reported companion candidates can be interpreted as slightly asymmetric disc emission or illumination.

3-D printed photoreceptor phantoms for evaluating lateral resolution of adaptive optics imaging systems.

With adaptive optics (AO), optical coherence tomography and scanning laser ophthalmoscopy imaging systems can resolve individual photoreceptor cells in living eyes, due to enhanced lateral spatial resolution. However, no standard test method exists for experimentally quantifying this parameter in ophthalmic AO imagers. Here, we present three-dimensional (3-D) printed phantoms, which enable the measurement of lateral resolution in an anatomically relevant manner. We used two-photon polymerization to fabricate two phantoms, which mimic the mosaic of cone photoreceptor outer segments at multiple retinal eccentricities. With these phantoms, we demonstrated that the resolution of two multimodal AO systems is similar to theoretical predictions, with some intriguing speckle effects.

Kepler-411: a four-planet system with an active host star

We present a detailed characterization of the Kepler-411 system (KOI 1781). This system was previously known to host two transiting planets: one with a period of 3 days (R = 2.4 R⊕; Kepler-411b) and one with a period of 7.8 days (R = 4.4 R⊕; Kepler-411c), as well as a transiting planetary candidate with a 58-day period (R = 3.3 R⊕; KOI 1781.03) from Kepler photometry. Here, we combine Kepler photometry data and new transit timing variation (TTV) measurements from all the Kepler quarters with previous adaptive-optics imaging results, and dynamical simulations, in order to constrain the properties of the Kepler-411 system. From our analysis, we obtain masses of 25.6 ± 2.6 M⊕ for Kepler-411b and 26.4 ± 5.9 M⊕ for Kepler-411c, and we confirm the planetary nature of KOI 1781.03 with a mass of 15.2 ± 5.1 M⊕, hence the name Kepler-411d. Furthermore, by assuming near-coplanarity of the system (mutual inclination below 30°), we discover a nontransiting planet, Kepler-411e, with a mass of 10.8 ± 1.1 M⊕ on a 31.5-day orbit, which has a strong dynamical interaction with Kepler-411d. With densities of 1.71 ± 0.39 g cm−3 and 2.32 ± 0.83 g cm−3, both Kepler-411c and Kepler-411d belong to the group of planets with a massive core and a significant fraction of volatiles. Although Kepler-411b has a sub-Neptune size, it belongs to the group of rocky planets.