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Interferometric telescope observations of the Jovian moon Io reveal that the floor of the Loki Patera volcano has been resurfaced in two waves, with different starting times and velocities. Volcanic resurfacing on Io Jupiter's moon Io has the biggest active volcano in the Solar System. Inside the volcano, a warm floor surrounds a cool central island. Previous observations have indicated that volcanic resurfacing occurs every one to three years, but telescope observations have insufficient resolution to see how this progresses, and spacecraft observations have not been able to see the entire floor at once. Katherine De Kleer et al . used an occultation of Io by another of Jupiter's moons (Europa) to map the entire floor at a spatial resolution of 2 kilometres, using interferometric telescope observations. They find that the resurfacing happens in two waves, with different starting times and velocities, which then converge around the central island. They interpret the differences between the waves as evidence of either a non-uniformity in the lava or variations in the bulk density of the crust across the volcano. The Jovian moon Io hosts the most powerful persistently active volcano in the Solar System, Loki Patera 1 , 2 . The interior of this volcanic, caldera-like feature is composed of a warm, dark floor covering 21,500 square kilometres 3 surrounding a much cooler central ‘island’ 4 . The temperature gradient seen across areas of the patera indicates a systematic resurfacing process 4 , 5 , 6 , 7 , 8 , 9 , which has been seen to occur typically every one to three years since the 1980s 5 , 10 . Analysis of past data has indicated that the resurfacing progressed around the patera in an anti-clockwise direction at a rate of one to two kilometres per day, and that it is caused either by episodic eruptions that emplace voluminous lava flows or by a cyclically overturning lava lake contained within the patera 5 , 8 , 9 , 11 . However, spacecraft and telescope observations have been unable to map the emission from the entire patera floor at sufficient spatial resolution to establish the physical processes at play. Here we report temperature and lava cooling age maps of the entire patera floor at a spatial sampling of about two kilometres, derived from ground-based interferometric imaging of thermal emission from Loki Patera obtained on 8 March 2015 ut as the limb of Europa occulted Io. Our results indicate that Loki Patera is resurfaced by a multi-phase process in which two waves propagate and converge around the central island. The different velocities and start times of the waves indicate a non-uniformity in the lava gas content and/or crust bulk density across the patera.

The SAGE-Spec Spitzer Legacy program is a spectroscopic follow-up to the SAGE-LMC photometric survey of the Large Magellanic Cloud carried out with theSpitzer Space Telescope. We present an overview of SAGE-Spec and some of its first results. The SAGE-Spec program aims to study the life cycle of gas and dust in the Large Magellanic Cloud and to provide information essential to the classification of the point sources observed in the earlier SAGE-LMC photometric survey. We acquired 224.6 h of observations using the infrared spectrograph and the spectral energy distribution (SED) mode of the Multiband Imaging Photometer forSpitzer. The SAGE-Spec data, along with archivalSpitzerspectroscopy of objects in the Large Magellanic Cloud, are reduced and delivered to the community. We discuss the observing strategy, the specific data-reduction pipelines applied, and the dissemination of data products to the scientific community. Initial science results include the first detection of an extragalactic 21 μm feature toward an evolved star and elucidation of the nature of disks around RV Tauri stars in the Large Magellanic Cloud. Toward some young stars, ice features are observed in absorption. We also serendipitously observed a background quasar, at a redshift of z ≈ 0.14 z ≈ 0.14 , which appears to be hostless.

The James Webb Space Telescope (JWST) offers unprecedented sensitivity, stability, and wavelength coverage for transiting exoplanet studies, opening up new avenues for measuring atmospheric abundances, structure, and temperature profiles. Taking full advantage of JWST spectroscopy of planets from 0.6 to 28 m, however, will require many observations with a combination of the NIRISS, NIRCam, NIRSpec, and MIRI instruments. In this white paper, we discuss a new NIRCam mode (not yet approved or implemented) that can reduce the number of necessary observations to cover the 1.0-5.0 m wavelength range. Even though NIRCam was designed primarily as an imager, it also includes several grisms for phasing and aligning JWST's 18 hexagonal mirror segments. NIRCam's long-wavelength channel includes grisms that cover 2.4-5.0 m with a resolving power of R = 1200-1550 using two separate configurations. The long-wavelength grisms have already been approved for science operations, including wide field and single object (time series) slitless spectroscopy. We propose a new mode that will simultaneously measure spectra for science targets in the 1.0-2.0 m range using NIRCam's short-wavelength channel. This mode, if approved, would take advantage of NIRCam's Dispersed Hartmann Sensor (DHS), which produces 10 spatially separated spectra per source at R ∼ 300. We discuss the added benefit of the DHS in constraining abundances in exoplanet atmospheres as well as its ability to observe the brightest systems. The DHS essentially comes for free (at no time cost) with any NIRCam long-wavelength grism observation, but the detector integration parameters have to be selected to ensure that the long-wavelength grism observations do not saturate and that JWST data volume downlink constraints are not violated. Combining both of NIRCam's channels will maximize the science potential of JWST, which is a limited life observatory.

Active galactic nuclei (AGNs) are a key component of galaxy evolution owing to feedback on the host from its supermassive black hole. The morphology of warm inflowing and outflowing dusty material can reveal the nature of the onset of feedback, AGN feeding and the unified model of AGN. Here we use the Large Binocular Telescope Interferometer (LBTI) to image the dense, obscuring disk and extended dusty outflow region of NGC 1068. In Fizeau imaging mode, the LBTI synthesizes the equivalent resolution of a 22.8 m telescope. The 8.7 μm Fizeau images of NGC 1068 have an effective resolution of 47 × 90 mas (3.3 × 6.2 pc) in a 5″ field of view after performing point spread function deconvolution techniques described here. This is the only extragalactic source to be Fizeau imaged using the LBTI, and the images bridge the scales measured with the Very Large Telescope Interferometer (0.5–5 pc) and those of single telescopes such as James Webb Space Telescope and Keck (>15 pc). The images detect and spatially resolve the low surface brightness mid-infrared features in the AGN disk/wind region that are overresolved by the Very Large Telescope Interferometer. The images show strong correlation between mid-infrared dust emission and near-infrared emission of highly excited atomic lines observed by SINFONI. Such LBTI imaging is a precursor to infrared imaging using the upcoming generation of extremely large telescopes, with angular resolutions up to six times better than James Webb Space Telescope, the largest space telescope in orbit. Detailed infrared images of the region around the supermassive black hole of NGC 1068 from the Large Binocular Telescope Interferometer reveal a dense disk, dusty outflow and emissions linked to radio jets, suggesting that active galactic nucleus torus models should include jet interactions.

The James Webb Space Telescope ( JWST) offers unprecedented sensitivity, stability, and wavelength coverage for transiting exoplanet studies, opening up new avenues for measuring atmospheric abundances, structure, and temperature profiles. Taking full advantage of JWST spectroscopy of planets from 0.6 to 28 μm, however, will require many observations with a combination of the NIRISS, NIRCam, NIRSpec, and MIRI instruments. In this white paper, we discuss a new NIRCam mode (not yet approved or implemented) that can reduce the number of necessary observations to cover the 1.0–5.0 μm wavelength range. Even though NIRCam was designed primarily as an imager, it also includes several grisms for phasing and aligning JWST’s 18 hexagonal mirror segments. NIRCam’s long-wavelength channel includes grisms that cover 2.4–5.0 μm with a resolving power of R = 1200–1550 using two separate configurations. The long-wavelength grisms have already been approved for science operations, including wide field and single object (time series) slitless spectroscopy. We propose a new mode that will simultaneously measure spectra for science targets in the 1.0–2.0 μm range using NIRCam’s shortwavelength channel. This mode, if approved, would take advantage of NIRCam’s Dispersed Hartmann Sensor (DHS), which produces 10 spatially separated spectra per source at R ∼ 300. We discuss the added benefit of the DHS in constraining abundances in exoplanet atmospheres as well as its ability to observe the brightest systems. The DHS essentially comes for free (at no time cost) with any NIRCam long-wavelength grism observation, but the detector integration parameters have to be selected to ensure that the long-wavelength grism observations do not saturate and that JWST data volume downlink constraints are not violated. Combining both of NIRCam’s channels will maximize the science potential of JWST, which is a limited life observatory.

The HOSTS (Hunt for Observable Signatures of Terrestrial Systems) survey searches for dust near the habitable zones (HZs) around nearby, bright main sequence stars. We use nulling interferometry in N band to suppress the bright stellar light and to probe for low levels of HZ dust around the 30 stars observed so far. Our overall detection rate is 18%, including four new detections, among which are the first three around Sun-like stars and the first two around stars without any previously known circumstellar dust. The inferred occurrence rates are comparable for early type and Sun-like stars, but decrease from 60 (+16/-21)% for stars with previously detected cold dust to 8 (+10/-3)% for stars without such excess, confirming earlier results at higher sensitivity. For completed observations on individual stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal excess luminosity function, we put upper limits on the median HZ dust level of 13 zodis (95% confidence) for a sample of stars without cold dust and of 26 zodis when focussing on Sun-like stars without cold dust. However, our data suggest that a more complex luminosity function may be more appropriate. For stars without detectable LBTI excess, our upper limits are almost reduced by a factor of two, demonstrating the strength of LBTI target vetting for future exo-Earth imaging missions. Our statistics are so far limited and extending the survey is critical to inform the design of future exo-Earth imaging surveys.

Recent disk observations have revealed multiple indirect signatures of forming gas giant planets, but high-contrast imaging has rarely confirmed the presence of the suspected perturbers. Here, we exploit a unique opportunity provided by the background star AS209bkg, which shines through a wide annular gap in the AS209 disk, to perform transmission spectrophotometry and directly measure the extinction from gap material for the first time. By combining new VLT/SPHERE and JWST/NIRCam observations with archival HST data from 2005, we model the spectral energy distribution (SED) of AS209bkg over a 19-year baseline. We find that the SED and its variability are best explained by increasing extinction along the line of sight as AS209bkg approaches the gap edge in projection. The extinction is best described by a combination of ISM-like extinction component and a grey extinction component. This points to the presence of grains in the disk outer gap that are larger than in the ISM. We find that the extinction in the gap at \\(4.0~\\)m is \\(A_4\\, = 2.7^+0.7_-0.7\\) mag, while at H\\(\\) (\\(=0.656~\\)m), where most searches for accretion signatures take place, the extinction could be as high as \\(A_H = 4.2^+0.9_-1.2\\) mag (\\(A_V=4.6^+1.0_-1.3\\) mag). This suggests that even wide, deep gaps can significantly obscure emission from protoplanets, even those following a hot-start evolutionary model. Our extinction measurements help reconcile the discrepancy between ALMA-based predictions of planet-disk interactions and the non-detections from sensitive optical and near-infrared imaging campaigns.

The Large Binocular Telescope Interferometer (LBTI) is a versatile instrument designed for high-angular resolution and high-contrast infrared imaging (1.5-13 microns). In this paper, we focus on the mid-infrared (8-13 microns) nulling mode and present its theory of operation, data reduction, and on-sky performance as of the end of the commissioning phase in March 2015. With an interferometric baseline of 14.4 meters, the LBTI nuller is specifically tuned to resolve the habitable zone of nearby main-sequence stars, where warm exozodiacal dust emission peaks. Measuring the exozodi luminosity function of nearby main-sequence stars is a key milestone to prepare for future exoEarth direct imaging instruments. Thanks to recent progress in wavefront control and phase stabilization, as well as in data reduction techniques, the LBTI demonstrated in February 2015 a calibrated null accuracy of 0.05% over a three-hour long observing sequence on the bright nearby A3V star beta Leo. This is equivalent to an exozodiacal disk density of 15 to 30 zodi for a Sun-like star located at 10pc, depending on the adopted disk model. This result sets a new record for high-contrast mid-infrared interferometric imaging and opens a new window on the study of planetary systems.

Context. Astrometric monitoring of directly-imaged exoplanets allows the study of their orbital parameters and system architectures. Because most directly-imaged planets have long orbital periods (>20 AU), accurate astrometry is challenging when based on data acquired on timescales of a few years and usually with different instruments. The LMIRCam camera on the LBT is being used for the LEECH survey to search for and characterize young and adolescent exoplanets in L' band, including their system architectures. Aims. We first aim to provide a good astrometric calibration of LMIRCam. Then, we derive new astrometry, test the predictions of the orbital model of 8:4:2:1 mean motion resonance proposed by Goździewski & Migaszewski, and perform new orbital fitting of the HR 8799 bcde planets. We also present deep limits on a putative fifth planet interior to the known planets. Methods. We use observations of HR 8799 and the Theta1 Ori C field obtained during the same run in October 2013. Results. We first characterize the distortion of LMIRCam. We determine a platescale and a true north orientation for the images of 10.707 +/- 0.012 mas/pix and -0.430 +/- 0.076 deg, respectively. The errors on the platescale and true north orientation translate into astrometric accuracies at a separation of 1 of 1.1 mas and 1.3 mas, respectively. The measurements for all planets are usually in agreement within 3 sigma with the ephemeris predicted by Goździewski & Migaszewski. The orbital fitting based on the new astrometric measurements favors an architecture for the planetary system based on 8:4:2:1 mean motion resonance. The detection limits allow us to exclude a fifth planet slightly brighter/more massive than HR 8799 b at the location of the 2:1 resonance with HR 8799 e (~9.5 AU) and about twice as bright as HR 8799 cde at the location of the 3:1 resonance with HR 8799 e (~7.5 AU).

We report on the first nulling interferometric observations with the Large Binocular Telescope Interferometer (LBTI), resolving the N' band (9.81 - 12.41 um) emission around the nearby main-sequence star eta Crv (F2V, 1-2 Gyr). The measured source null depth amounts to 4.40% +/- 0.35% over a field-of-view of 140 mas in radius (~2.6\\,AU at the distance of eta Corvi) and shows no significant variation over 35{\\deg} of sky rotation. This relatively low null is unexpected given the total disk to star flux ratio measured by Spitzer/IRS (~23% across the N' band), suggesting that a significant fraction of the dust lies within the central nulled response of the LBTI (79 mas or 1.4 AU). Modeling of the warm disk shows that it cannot resemble a scaled version of the Solar zodiacal cloud, unless it is almost perpendicular to the outer disk imaged by Herschel. It is more likely that the inner and outer disks are coplanar and the warm dust is located at a distance of 0.5-1.0 AU, significantly closer than previously predicted by models of the IRS spectrum (~3 AU). The predicted disk sizes can be reconciled if the warm disk is not centrosymmetric, or if the dust particles are dominated by very small grains. Both possibilities hint that a recent collision has produced much of the dust. Finally, we discuss the implications for the presence of dust at the distance where the insolation is the same as Earth's (2.3 AU).