AO Imaging Research Articles

Comparison of the Photoreceptor Mosaic Before and After Macular Hole Surgery with High Resolution Adaptive Optics Imaging

PurposeTo assess the photoreceptor mosaic in patients with idiopathic full thickness macular hole (MH) before and after pars plana vitrectomy (PPV) with adaptive optics enhanced retinal imaging (AO). DesignProspective case series. MethodsProspective cohort study of patients who presented at the Kensington Eye Institute, Toronto, Canada with a diagnosis of macular hole treated with PPV. Exclusion criteria: secondary MH, high myopia (axial length >26.5 mm), media opacity precluding OCT or AO imaging, previous intraocular surgery except for cataract extraction. Imaging using an AO fundus camera (Imagine Eyes, RTX1) was performed preoperatively and 3-months following successful MH repair in both eyes. Cone density (CD), regularity, dispersion, regularity, dispersion, and spacing were measured at 2° and 4° of eccentricity in 4 quadrants (superior, inferior, nasal, and temporal) with pre- and postoperative values compared. ResultsWe included 18 eyes of 9 patients. At 2° there was significant reduction in CD and increase in spacing and dispersion and a non-significant change in regularity post-operatively. Comparison between preoperative and postoperative measurements at 2° mean (Standard Error= SE) were: CD: 14612 ± 3003 and 12280 ± 4632 photoreceptors/mm2 [95%CIs= -2413 to -702] p=0.0004, regularity: 88 ± 7% and 84 ± 12% [95%CIs= -4.67 to 0.04] p=0.054, dispersion: 19 ± 6% and 23 ± 10% [95%CIs= 0.5 to 4.24] p=0.013, spacing: 9 ± 1 microns and 10 ± 2microns [95%CIs= 0.40 to 1.27] p=0.0002; at 4° was: CD: 13377 ± 4339 and 12770 ± 4391 photoreceptors/mm2 [95%CIs= -1368 to 252] p=0.176, regularity:87 ± 9% and 86 ± 12% [95%CIs= -4.65 to 0.08] p=0.74, dispersion: 20 ± 8% and 20 ±9 % [95%CIs= -2.11 to 1.5] p=0.74, spacing:10 ± 2 microns and 10 ± 3 microns [95%CIs= -0.23 to 0.58] p=0.39. ConclusionAdaptive optics imaging allows quantitative assessment of the photoreceptor mosaic pre- and post-PPV in patients with MH. There was a significant change to the photoreceptor mosaic related to the MH at 2° pre- and post-operatively. AO imaging enables high-resolution investigation of the photoreceptor remodeling process following surgery, which may allow for a more thorough assessment of surgical outcomes.

The puzzling north polar region of Uranus: Continued zero-shear winds and increasing brightness from 2015 through 2022 according to 7 years of Keck AO imaging

There may be a permanent north–south asymmetry in the zonal wind profile of Uranus. According to high signal-to-noise near-IR observations with the Keck telescope NIRC2 camera, through 2014 the winds north of 60∘N had a constant (zero shear) longitudinal drift rate of 4.1∘/h westward (Sromovsky et al., 2015). Yet the south polar winds in 1986 had strong latitudinal shear, reaching speeds of 8.5∘/h (Karkoschka, 2015). If that asymmetry were a result of extreme seasonal forcing, it might be expected to reverse before the 2030 solstice. However, continued high signal-to-noise near-IR observations from 2015 through 2022 provide little evidence that the north polar winds have changed at all, although there have been changes in the distribution of cloud features used to track those winds and an increase in the brightness of the background haze that makes it harder to detect these small low-contrast features. Between 2015 and 2017, a gap in easily trackable features developed in the 55∘N–60∘N latitude region, and at the northern edge of that gap there was a hint that a dramatic change to the inverted profile might be starting. To further investigate that possible change and to fill in the gap, we developed a new wind measurement technique that was more sensitive to low-contrast spatial structure. Our new method does not confirm any significant wind speed change in the gap, nor at its northern edge.The lifetimes of many of the small discrete polar features are surprisingly long. Many were tracked over time spans over 24 h, and some lasted for weeks. More prominent features seen at low latitudes seem to persist for multiple years and vary in latitude and drift rate in a cyclical fashion. While measurements so far favor a permanent asymmetry in the zonal wind profile of Uranus, the possibility remains that a dramatic circulation change might take place between 2022 and the next solstice in 2030. Using simplified radiation transfer modeling we infer a largely unchanging upper layer of small particles of very low optical depth vertically distributed above an active deeper mid-level layer, at an effective pressure of ∼2–2.5 bar. That middle layer increased in reflectivity at 1.6 μm by more than a factor of 2 from 2015 to 2022 and is the main source of the top-of-atmosphere brightness increase seen over that period, rather than any significant temporal change in polar methane abundance.

Adaptive optics retinal imaging in patients with usher syndrome.

To determine the structure of the cone photoreceptor mosaic in the macula in eyes with retinitis pigmentosa related to Usher syndrome using adaptive optics fundus (AO) imaging and to correlate these findings with those of the standard clinical diagnostics. Ten patients with a genetically confirmed retinitis pigmentosa in Usher syndrome due to biallelic variants in MYO7A or USH2A were enrolled in the study. All patients underwent a complete ophthalmological examination including best corrected visual acuity (BCVA), spectral-domain optical coherence tomography (SD-OCT) with fundus autofluorescence photography (FAF), full-field (ffERG) and multifocal electroretinography (mfERG) and Adaptive Optics Flood Illuminated Ophthalmoscopy (AO, rtx1™, Imagine Eyes, Orsay, France). The cone density was assessed centrally and at each 0.5 degree horizontally and vertically from 1-4 degree of eccentricity. In the AO images, photoreceptor cell death was visualized as a disruption of the cone mosaic and low cone density. In the early stage of the disease, cones were still visible in the fovea, whereas outside the fovea a loss of cones was recognizable by blurry, dark patches. The blurry patches corresponded to the parafoveal hypofluorescent ring in the FAF images and the beginning loss of the IS/OS line and external limiting membrane in the SD-OCT images. FfERGs were non-recordable in 7 patients and reduced in 3. The mfERG was reduced in all patients and correlated significantly (p <0.001) with the cone density. The kinetic visual field area, measured with III4e and I4e, did not correlate with the cone density. The structure of the photoreceptors in Usher syndrome patients were detectable by AO fundus imaging. The approach of using high-resolution technique to assess the photoreceptor structure complements the established clinical examinations and allows a more sensitive monitoring of early stages of retinitis pigmentosa in Usher syndrome.

Absolute retinal blood flow in healthy eyes and in eyes with retinal vein occlusion

PurposeTo measure non-invasively retinal venous blood flow (RBF) in healthy subjects and patients with retinal venous occlusion (RVO). MethodsThe prototype named AO-LDV (Adaptive Optics Laser Doppler Velocimeter), which combines a new absolute laser Doppler velocimeter with an adaptive optics fundus camera (rtx1, Imagine Eyes®, Orsay, France), was studied for the measurement of absolute RBF as a function of retinal vessel diameters and simultaneous measurement of red blood cell velocity. RBF was measured in healthy subjects (n = 15) and patients with retinal venous occlusion (RVO, n = 6). We also evaluated two softwares for the measurement of retinal vessel diameters: software 1 (automatic vessel detection, profile analysis) and software 2 (based on the use of deep neural networks for semantic segmentation of vessels, using a M2u-Net architecture). ResultsSoftware 2 provided a higher rate of automatic retinal vessel measurement (99.5 % of 12,320 AO images) than software 1 (64.9 %) and wider measurements (75.5 ± 15.7 μm vs 70.9 ± 19.8 μm, p < 0.001). For healthy subjects (n = 15), all the retinal veins in one eye were measured to obtain the total RBF. In healthy subjects, the total RBF was 37.8 ± 6.8 μl/min. There was a significant linear correlation between retinal vessel diameter and maximal velocity (slope = 0.1016; p < 0.001; r2 = 0.8597) and a significant power curve correlation between retinal vessel diameter and blood flow (3.63 × 10−5 × D2.54; p < 0.001; r2 = 0.7287). No significant relationship was found between total RBF and systolic and diastolic blood pressure, ocular perfusion pressure, heart rate, or hematocrit. For RVO patients (n = 6), a significant decrease in RBF was noted in occluded veins (3.51 ± 2.25 μl/min) compared with the contralateral healthy eye (11.07 ± 4.53 μl/min). For occluded vessels, the slope between diameter and velocity was 0.0195 (p < 0.001; r2 = 0.6068) and the relation between diameter and flow was Q = 9.91 × 10−6 × D2.41 (p < 0.01; r2 = 0.2526). ConclusionThis AO-LDV prototype offers new opportunity to study RBF in humans and to evaluate treatment in retinal vein diseases.

Binarity and beyond in A stars II. Disentangling the four stars in the vicinity of the triple HIP 87813 within the quintuple system HJ2814

ABSTRACT A-type stars are the progenitors of about half of the white dwarfs (WDs) that currently exist. The observational mappings of both multiplicities are far from complete and their connection is not known. We are in the process of obtaining tight constraints on a sample of 108 southern and nearby A-stars that are part of the VAST sample by conducting near-infrared (NIR) interferometric observations to the stars among them which have large Gaia-Hipparcos accelerations. In this paper, we combine spectroscopy, adaptive optics imaging, NIR interferometry, and Gaia-Hipparcos astrometry in order to disentangle the stars in the complicated HIP 87813 = HJ2814A system. We show that (i) a previously discovered faint star separated by 2 arcsec is actually a background source; (ii) the Gaia-Hipparcos acceleration is caused by a newly discovered M ∼ 0.77 M⊙ star that was missed in previous AO images and we solve for its a = 27 au (P ∼ 70 yrs) astrometric orbit; (iii) by combining archival spectra with interferometric observations, we show that the A star has a very close M ∼ 0.85 M⊙ companion on a a = 0.16 au (P = 13.4 d) orbit. The mutual inclination in the hierarchical triple is constrained to $\phi _{\mathrm{rel}}=46\pm 15^{^{\circ }}$ but Kozai–Lidov eccentricity oscillations in the inner binary are currently very small and damped by general relativistic precession. The system HJ2814 is one of only about fifteen known 5+ multiples with an A-star primary, and will result in a system of at least two WDs within about a Hubble time.

A Dearth of Close-in Stellar Companions to M-dwarf TESS Objects of Interest

TESS has proven to be a powerful resource for finding planets, including those that orbit the most prevalent stars in our galaxy: M dwarfs. Identification of stellar companions (both bound and unbound) has become a standard component of the transiting planet confirmation process in order to assess the level of light-curve dilution and the possibility of the target being a false positive. Studies of stellar companions have also enabled investigations into stellar multiplicity in planet-hosting systems, which has wide-ranging implications for both exoplanet detection and characterization, as well as for the formation and evolution of planetary systems. Speckle and AO imaging are some of the most efficient and effective tools for revealing close-in stellar companions; we therefore present observations of 58 M-dwarf TOIs obtained using a suite of speckle imagers at the 3.5 m WIYN telescope, the 4.3 m Lowell Discovery Telescope, and the 8.1 m Gemini North and South telescopes. These observations, as well as near-infrared adaptive optics images obtained for a subset (14) of these TOIs, revealed only two close-in stellar companions. Upon surveying the literature, and cross-matching our sample with Gaia, SUPERWIDE, and the catalog from El-Badry et al., we reveal an additional 15 widely separated common proper motion companions. We also evaluate the potential for undetected close-in companions. Taking into consideration the sensitivity of the observations, our findings suggest that the orbital period distribution of stellar companions to planet-hosting M dwarfs is shifted to longer periods compared to the expected distribution for field M dwarfs.

Zodiacal exoplanets in time (ZEIT) XII: a directly imaged planetary-mass companion to a young Taurus M dwarf star

ABSTRACT We report the discovery of a resolved (0.9 arcsec) substellar companion to a member of the 1–5 Myr Taurus star-forming region. The host star (2M0437) is a single mid-M type (Teff ≈ 3100 K) dwarf with a position, space motion, and colour–magnitude that support Taurus membership, and possible affiliation with a ∼2.5-Myr-old subgroup. A comparison with stellar models suggests a 2–5 Myr age and a mass of 0.15–0.18M⊙. Although K2 detected quasi-periodic dimming from close-in circumstellar dust, the star lacks detectable excess infrared emission from a circumstellar disc and its H α emission is not commensurate with accretion. Astrometry based on 3 yr of AO imaging shows that the companion (2M0437b) is comoving, while photometry of two other sources at larger separation indicates that they are likely heavily reddened background stars. A comparison of the luminosity of 2M0437b with models suggests a mass of 3–5 MJUP, well below the deuterium burning limit, and an effective temperature of 1400–1500 K, characteristic of a late L spectral type. The H − K colour is redder than the typical L dwarf, but comparable to other directly detected young planets, e.g. those around HR 8799. The discovery of a super-Jupiter around a very young, very low-mass star challenges models of planet formation by either core accretion (which requires time) or disc instability (which requires mass). We also detected a second, comoving, widely separated (75 arcsec) object that appears to be a heavily extincted star. This is certainly a fellow member of this Taurus subgroup and statistically likely to be a bound companion.

Planetary candidates transiting cool dwarf stars from campaigns 12 to 15 of K2

ABSTRACT We analysed the photometry of 20 038 cool stars from campaigns 12, 13, 14, and 15 of the K2 mission in order to detect, characterize, and validate new planetary candidates transiting low-mass stars. We present a catalogue of 25 new periodic transit-like signals in 22 stars, of which we computed the parameters of the stellar host for 19 stars and the planetary parameters for 21 signals. We acquired speckle and AO images, and also inspected archival Pan-STARRS1 images and Gaia DR2 to discard the presence of close stellar companions and to check possible transit dilutions due to nearby stars. False positive probability (FPP) was computed for 22 signals, obtaining FPP &amp;lt; $1{{\ \rm per\ cent}}$ for 17. We consider 12 of them as statistically validated planets. One signal is a false positive and the remaining 12 signals are considered as planet candidates. 20 signals have an orbital period of P$_{\rm orb} \lt 10\,\mathrm{ d}$, 2 have $10\, \mathrm{ d} \lt $ P$_{\rm orb} \lt 20\, \mathrm{ d}$, and 3 have P$_{\rm orb} \gt 20\, \mathrm{ d}$. Regarding radii, 11 candidates and validated planets have computed radius R &amp;lt; 2R⊕, 9 have 2R⊕ &amp;lt; R &amp;lt; 4R⊕, and 1 has R &amp;gt; 4R⊕. Two validated planets and two candidates are located in moderately bright stars ($\rm \mathit{ m}_{kep}\lt 13$) and two validated planets and three candidates have derived orbital radius within the habitable zone according to optimistic models. Of special interest is the validated warm super-Earth K2-323 b (EPIC 248616368 b) with T$_{\rm eq} = 318^{+24}_{-43} \, \mathrm{ K}$, S$_{\rm p} = 1.7\pm 0.2 \, \mathrm{ S}_{\oplus }$, and R$_{\rm p} = 2.1\pm 0.1 \, \mathrm{ R}_{\oplus }$, located in an m$\rm _{kep}$ = 14.13 star.

New Frontiers in Noninvasive Analysis of Retinal Wall-to-Lumen Ratio by Retinal Vessel Wall Analysis.

PurposeTo compare measurement of wall-to-lumen ratio (WLR) by means of high-resolution adaptive optics imaging (AO) with intuitive to use retinal vessel wall (VW) analysis (VWA). Moreover, to validate the techniques by comparing WLR of healthy young (HY) with healthy older patients.MethodsTen retinal VW images of 13 HY (24 ± 2 years) and 16 healthy older (60 ± 8 years) were obtained with AO and VWA. The average of five measurements of VW, retinal vessel lumen and WLR of a single vessel from AO and VWA were calculated and compared.ResultsWLR of AO and VWA images showed high correlations, r = 0.75, t(27) = 5.98, P < .001, but differed systematically (WLR: VWA, 40 ± 7% and AO, 35 ± 9%; P < .001). Comparable patterns were found for VW and vessel lumen. HY showed significantly lower WLR (AO, 31 ± 8% and VWA, 36 ± 8%) compared with healthy older (AO, 39 ± 9% [P = .012]; VWA, 42 ± 5% [P = .013]).ConclusionsAssessment of WLR by VWA showed a good correlation with laborious analysis of the microstructure by high-resolution AO. Measurement of WLR in different age groups indicated good validity. Deviations in VW, vessel lumen, and WLR between AO and VWA can be explained by systematic differences in image scale and resolution. Future studies are needed to investigate the clinical relevance of microvascular WLR assessment by retinal VWA and its prognostic value.Translational RelevanceAdditional assessment of retinal WLR by use of digital VWA to evaluate microstructural remodeling may prove to be a valuable extension to the current use of retinal vessel diameters as biomarkers of cardiovascular risk.

DeepAO: Efficient Screen Space Ambient Occlusion Generation via Deep Network

Ambient occlusion ( abbr . AO) plays an important role in realistic rendering applications because AO produces more realistic ambient lighting, which is achieved by calculating the brightness of certain screen parts based on objects’ geometry. However, the baseline computation of AO algorithm is time-consuming, which limits its application for real-time rendering. Currently, most AO algorithms are based on screen space to reduce the computational consumption, which leads to unrealistic results due to the usage of artificial features. To overcome these challenges, in this paper, we first create a well-crafted dataset with the pair of deferred shading buffer data and ground-truth AO shaded images. Then, we design an efficient deep neural network for the screen space AO image generation, based on which we further design a Compute Shader Library to compute the shaded AO images. Our extensive experimental results show that our method achieves competent performance than existing screen space ambient or volumetric ambient based AO methods both in visual quality and efficiency.

Morphologic and Functional Assessment of Photoreceptors After Macula-Off Retinal Detachment With Adaptive-Optics OCT and Microperimetry

Limited information is available on morphologic and functional regeneration of photoreceptors after retinal detachment (RD) surgery. This observational clinical study compared morphologic and functional changes of cones after vitrectomy for macula-off retinal detachment. Prospective, fellow-eye comparative case series. StudyPopulation: Five eyes after vitrectomy with gas for macula-off retinal detachment (retinal detachment eyes, RDE) and 5 healthy fellow eyes (HFE) of 5 patients (mean age 59.8 years, macula-off duration 0.5days to 5.5days). ObservationProcedures: Eyes were examined with adaptive-optics optical coherence tomography (AO-OCT), spectral-domain OCT (SDOCT), and microperimetry (MP) at 6 (baseline, BL) and 56weeks (follow-up, FUP) after 23 gauge pars plana vitrectomy and SF6 gas tamponade. Eight corresponding regions at foveal eccentricities of 2.5° (ecc 2.5°) and 6.5° (ecc 6.5°) were analyzed in every eye. AO-OCT en face images and SD-OCT B-scans were graded regarding irregularity and loss of photoreceptor signals ranging from none to severe changes. The number of detectable cones at height of the inner-outer segment junction (IS/OS) and cone outer segment tips (COST) was counted manually in AO-OCT images. MP with a custom grid was used to assess retinal sensitivity at these locations. MainOutcomeMeasures: Cone density, cone pattern regularity and signal attenuation, retinal sensitivity. In comparison to HFE, RDE showed highly irregular cone patterns in AO-OCT and irregular outer retinal bands in SDOCT. Despite significant improvement of cone pattern regularity compared to BL (P < .001), 63% of AO images showed remaining cone pattern irregularity and 45.5% of SDOCT B-scans showed severe signal reduction at FUP. In HFE, mean cone density retrieved from IS/OS and COST remained around 20,000/mm2 (ecc 2.5°) and 16,000/mm2 (ecc 6.5°) at BL and FUP. Cone density of RDE was significantly reduced and ranged between 200/mm2 and 15,600/mm2 (P < .001) at BL. Despite improvement at FUP (P < .001), mean cone density at IS/OS and COST was still lower compared to HFE and ranged between 7790 and 9555 cones/mm2 (P < .001). Mean retinal sensitivity of all measured locations remained 18 dB in HFE and was significantly lower in RDE, with 14.30 dB at BL and 14.64 dB at FUP. Both SDOCT grading and microperimetry sensitivity showed strong correlation with AO-OCT grading and cone density (rho values > 0.750). The combination of AO-OCT, SDOCT, and microperimetry is a powerful tool to capture cone regeneration after vitreoretinal surgery. Our study shows that cone morphology and function improve within 56weeks after RD surgery but structural and functional impairment is still present.

FLAMINGOS-2 Infrared Photometry of 2I/Borisov

2I/Borisov is the second interstellar object (ISO) after 'Oumuamua (Meech et al. 2017), but differs from 'Oumuamua drastically with its extensive cometary activity. A key ingredient to understand the nature of this comet is its size. However, due to its cometary activity and extended coma in the optical, only rough estimates and upper limits can be made for 2I/Borisov, ranging in a wide spread from 0.7 to 3.8 km (Guzik et al. 2019; Fitzsimmons et al. 2019; Jewitt, & Luu 2019; Bolin et al. 2019). It has been shown that observations at longer wavelengths (i.e. infrared) are less susceptible to the effects of coma, and can provide a better estimate of the size of the comet nucleus (see, e.g., Fern\'andez et al. 2013; Bauer et al. 2017). Here we present an estimate of the nucleus of 2I/Borisov from infrared observations by FLAMINGOS-2 on-board the Gemini South telescope (under Fast Turnaround program GS-2019B-FT-207), and infer a comet nucleus size of 1.5 km, comparable to but more stringent than the estimate from Keck AO imaging by Bolin et al. (2019).

Investigating the origin of the spectral line profiles of the Hot Wolf–Rayet Star WR 2

The hot WN star WR2 (HD6327) has been claimed to have many singular characteristics. To explain its unusually rounded and relatively weak emission line profiles, it has been proposed that WR2 is rotating close to break-up with a magnetically confined wind. Alternatively, the line profiles could be explained by the dilution of WR2's spectrum by that of a companion. In this paper, we present a study of WR2 using near-infrared AO imaging and optical spectroscopy and polarimetry. Our spectra reveal the presence of weak photospheric absorption lines from a ~B2.5-4V companion, which however contributes only ~5-10% to the total light, suggesting that the companion is a background object. Therefore, its flux cannot be causing any significant dilution of the WR star's emission lines. The absence of intrinsic linear continuum polarization from WR2 does not support the proposed fast rotation. Our Stokes V spectrum was not of sufficient quality to test the presence of a moderately strong organized magnetic field but our new modelling indicates that to confine the wind the putative magnetic field must be significantly stronger than was previously suggested sufficiently strong as to make its presence implausible.

An Excess of Jupiter Analogs in Super-Earth Systems

Abstract We use radial velocity (RV) observations to search for long-period gas giant companions in systems hosting inner super-Earth (1–4 R ⊕, 1–10 M ⊕) planets to constrain formation and migration scenarios for this population. We consistently refit published RV data sets for 65 stars and find nine systems with statistically significant trends indicating the presence of an outer companion. We combine these RV data with AO images to constrain the masses and semi-major axes of these companions. We quantify our sensitivity to the presence of long-period companions by fitting the sample with a power-law distribution and find an occurrence rate of 39% ± 7% for companions 0.5–20 M Jup and 1–20 au. Half of our systems were discovered by the transit method, and half were discovered by the RV method. While differences in the RV baselines and number of data points between the two samples lead to different sensitivities to distant companions, we find that occurrence rates of gas giant companions in each sample are consistent at the 0.5σ level. We compare the frequency of Jupiter analogs in these systems to the equivalent rate from field star surveys and find that Jupiter analogs are more common around stars hosting super-Earths. We conclude that the presence of outer gas giants does not suppress the formation of inner super-Earths, and that these two populations of planets instead appear to be correlated. We also find that the stellar metallicities of systems with gas giant companions are higher than those without companions, in agreement with the well-established metallicity correlation from RV surveys of field stars.

K2-290: a warm Jupiter and a mini-Neptune in a triple-star system

We report the discovery of two transiting planets orbiting K2-290 (EPIC 249624646), a bright (V=11.11) late F-type star residing in a triple-star system. It was observed during Campaign 15 of the K2 mission, and in order to confirm and characterise the system, follow-up spectroscopy and AO imaging were carried out using the FIES, HARPS, HARPS-N, and IRCS instruments. From AO imaging and Gaia data we identify two M-dwarf companions at a separation of $113 \pm 2$ AU and $2467_{-155}^{+177}$ AU. From radial velocities, K2 photometry, and stellar characterisation of the host star, we find the inner planet to be a mini-Neptune with a radius of $3.06 \pm 0.16 R_{\oplus}$ and an orbital period of $P = 9.2$ days. The radius of the mini-Neptune suggests that the planet is located above the radius valley, and with an incident flux of $F\sim 400 F_{\oplus}$, it lies safely outside the super-Earth desert. The outer warm Jupiter has a mass of $0.774\pm 0.047 M_{\rm J}$ and a radius of $1.006\pm 0.050R_{\rm J}$, and orbits the host star every 48.4 days on an orbit with an eccentricity $e<0.241$. Its mild eccentricity and mini-Neptune sibling suggest that the warm Jupiter originates from in situ formation or disk migration.

Exoplanets: Past, Present, and Future

Our understanding of extra-solar planet systems is highly driven by advances in observations in the past decade. Thanks to high precision spectrographs, we are able to reveal unseen companions to stars with the radial velocity method. High precision photometry from the space, especially with the Kepler mission, enables us to detect planets when they transit their stars and dim the stellar light by merely one percent or smaller. Ultra wide-field, high cadence, continuous monitoring of the Galactic bulge from different sites around the southern hemisphere provides us the opportunity to observe microlensing effects caused by planetary systems from the solar neighborhood, all the way to the Milky Way center. The exquisite AO imaging from ground-based large telescopes, coupled with high-contrast coronagraph, captured the photons directly emitted by planets around other stars. In this article, I present a concise review of the extra-solar planet discoveries, discussing the strengths and weaknesses of the major planetary detection methods, providing an overview of our current understanding of planetary formation and evolution given the tremendous observations delivered by various methods, as well as on-going and planned observation endeavors to provide a clear picture of extra-solar planetary systems.

The Magellanic Bridge Cluster NGC 796: Deep Optical AO Imaging Reveals the Stellar Content and Initial Mass Function of a Massive Open Cluster

Abstract NGC 796 is a massive young cluster located 59 kpc from us in the diffuse intergalactic medium of the 1/5–1/10 Z ☉ Magellanic Bridge, allowing us to probe variations in star formation and stellar evolution processes as a function of metallicity in a resolved fashion, and providing a link between resolved studies of nearby solar-metallicity and unresolved distant metal-poor clusters located in high-redshift galaxies. In this paper, we present adaptive optics griHα imaging of NGC 796 (at 0.″5, which is ∼0.14 pc at the cluster distance) along with optical spectroscopy of two bright members to quantify the cluster properties. Our aim is to explore whether star formation and stellar evolution vary as a function of metallicity by comparing the properties of NGC 796 to higher-metallicity clusters. We find an age of 20 − 5 + 12 Myr from isochronal fitting of the cluster main sequence in the color–magnitude diagram. Based on the cluster luminosity function, we derive a top-heavy stellar initial mass function (IMF) with a slope α = 1.99 ± 0.2, hinting at a metallicity and/or environmental dependence of the IMF, which may lead to a top-heavy IMF in the early universe. Study of the Hα emission-line stars reveals that classical Be stars constitute a higher fraction of the total B-type stars when compared with similar clusters at greater metallicity, providing some support to the chemically homogeneous theory of stellar evolution. Overall, NGC 796 has a total estimated mass of 990 ± 200 M ⊙, and a core radius of 1.4 ± 0.3 pc, which classifies it as a massive young open cluster, unique in the diffuse interstellar medium of the Magellanic Bridge.

K2-137 b: an Earth-sized planet in a 4.3-h orbit around an M-dwarf

We report the discovery from K2 of a transiting terrestrial planet in an ultra-short-period orbit around an M3-dwarf. K2-137 b completes an orbit in only 4.3 hours, the second-shortest orbital period of any known planet, just 4 minutes longer than that of KOI 1843.03, which also orbits an M-dwarf. Using a combination of archival images, AO imaging, RV measurements, and light curve modelling, we show that no plausible eclipsing binary scenario can explain the K2 light curve, and thus confirm the planetary nature of the system. The planet, whose radius we determine to be 0.89 +/- 0.09 Earth radii, and which must have a iron mass fraction greater than 0.45, orbits a star of mass 0.463 +/- 0.052 Msol and radius 0.442 +/- 0.044 Rsol.

KELT-20b: A Giant Planet with a Period of P ∼ 3.5 days Transiting the V ∼ 7.6 Early A Star HD 185603

Abstract We report the discovery of KELT-20b, a hot Jupiter transiting a early A star, HD 185603, with an orbital period of days. Archival and follow-up photometry, Gaia parallax, radial velocities, Doppler tomography, and AO imaging were used to confirm the planetary nature of KELT-20b and characterize the system. From global modeling we infer that KELT-20 is a rapidly rotating ( ) A2V star with an effective temperature of K, mass of , radius of , surface gravity of , and age of . The planetary companion has a radius of , a semimajor axis of au, and a linear ephemeris of . We place a upper limit of on the mass of the planet. Doppler tomographic measurements indicate that the planetary orbit normal is well aligned with the projected spin axis of the star ( ). The inclination of the star is constrained to , implying a three-dimensional spin–orbit alignment of . KELT-20b receives an insolation flux of , implying an equilibrium temperature of of ∼2250 K, assuming zero albedo and complete heat redistribution. Due to the high stellar , KELT-20b also receives an ultraviolet (wavelength nm) insolation flux of , possibly indicating significant atmospheric ablation. Together with WASP-33, Kepler-13 A, HAT-P-57, KELT-17, and KELT-9, KELT-20 is the sixth A star host of a transiting giant planet, and the third-brightest host (in V) of a transiting planet.

The Multiplicity of M Dwarfs in Young Moving Groups

Abstract We image 104 newly identified low-mass (mostly M-dwarf) pre-main sequence (PMS) members of nearby young moving groups (YMGs) with Magellan Adaptive Optics (MagAO) and identify 27 stellar binaries with instantaneous projected separation as small as 40 mas. Fifteen were previously unknown. The total number of multiple systems in this sample including spectroscopic and visual binaries from the literature is 36, giving a raw stellar multiplicity rate of at least for this population. In the separation range of roughly 1–300 au in which infrared AO imaging is most sensitive, the raw multiplicity rate is at least for binaries resolved by the MagAO infrared camera (Clio). The M-star subsample of 87 stars yields a raw multiplicity of at least over all separations, for secondary companions resolved by Clio from 1 to 300 au ( for all known binaries in this separation range). A combined analysis with binaries discovered by the Search for Associations Containing Young stars shows that stellar multiplicity fraction as a function of mass over the range of 0.2 to 1.2 M ☉ appears to be linearly flat, in contrast to the field, where multiplicity increases with mass. After bias corrections are applied, the multiplicity of low-mass YMG members (0.2–0.6 M ☉) is in excess of the field. The overall multiplicity fraction is also consistent with being constant in age and across YMGs, which suggests that multiplicity rates for this mass range are largely set by 10 Myr without appreciable evolution thereafter.