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Research output, citation impact, and the most-cited recent papers from NASA Research Park (United States). Aggregated across the NobleBlocks index of 300M+ scholarly works.

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2.1K
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95.1K
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NASA Research Park

Top-cited papers from NASA Research Park

The human gene for vascular endothelial growth factor. Multiple protein forms are encoded through alternative exon splicing
E. Tischer, R. Mitchell, Thomas G. Hartman, M. Silva +3 more
1991· Journal of Biological Chemistry2.0Kdoi:10.1016/s0021-9258(18)99049-6

Vascular endothelial growth factor (VEGF) is an apparently endothelial cell-specific mitogen that is structurally related to platelet-derived growth factor. By Northern blot and protein analyses, we show that VEGF is produced by cultured vascular smooth muscle cells. Analysis of VEGF transcripts in these cells by polymerase chain reaction and cDNA cloning revealed three different forms of the VEGF coding region, as had been reported in HL60 cells. The three forms of the human VEGF protein chain predicted from these coding regions are 189, 165, and 121 amino acids in length. Comparison of cDNA nucleotide sequences with sequences derived from human VEGF genomic clones indicates that the VEGF gene is split among eight exons and that the various VEGF coding region forms arise from this gene by alternative splicing: the 165-amino-acid form of the protein is missing the residues encoded by exon 6, whereas the 121-amino-acid form is missing the residues encoded by exons 6 and 7. Analysis of the VEGF gene promoter region revealed a single major transcription start, which lies near a cluster of potential Sp1 factor binding sites. The promoter region also contains several potential binding sites for the transcription factors AP-1 and AP-2; consistent with the presence of these sites, Northern blot analysis demonstrated that the level of VEGF transcripts is elevated in cultured vascular smooth muscle cells after treatment with the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate.

An introduction to wavelets
A. L. Graps
1995· IEEE Computational Science and Engineering1.8Kdoi:10.1109/99.388960

Wavelets were developed independently by mathematicians, quantum physicists, electrical engineers and geologists, but collaborations among these fields during the last decade have led to new and varied applications. What are wavelets, and why might they be useful to you? The fundamental idea behind wavelets is to analyze according to scale. Indeed, some researchers feel that using wavelets means adopting a whole new mind-set or perspective in processing data. Wavelets are functions that satisfy certain mathematical requirements and are used in representing data or other functions. Most of the basic wavelet theory has now been done. The mathematics have been worked out in excruciating detail, and wavelet theory is now in the refinement stage. This involves generalizing and extending wavelets, such as in extending wavelet packet techniques. The future of wavelets lies in the as-yet uncharted territory of applications. Wavelet techniques have not been thoroughly worked out in such applications as practical data analysis, where, for example, discretely sampled time-series data might need to be analyzed. Such applications offer exciting avenues for exploration.>

The grand challenges of <i>Science Robotics</i>
Guang‐Zhong Yang, Jim Bellingham, Pierre E. Dupont, Peer Fischer +4 more
2018· Science Robotics1.2Kdoi:10.1126/scirobotics.aar7650

is to deeply root robotics research in science while developing novel robotic platforms that will enable new scientific discoveries. Of our 10 grand challenges, the first 7 represent underpinning technologies that have a wider impact on all application areas of robotics. For the next two challenges, we have included social robotics and medical robotics as application-specific areas of development to highlight the substantial societal and health impacts that they will bring. Finally, the last challenge is related to responsible innovation and how ethics and security should be carefully considered as we develop the technology further.

CHARACTERISTICS OF PLANETARY CANDIDATES OBSERVED BY<i>KEPLER</i>. II. ANALYSIS OF THE FIRST FOUR MONTHS OF DATA
W. J. Borucki, David Koch, Gibor Basri, Natalie M. Batalha +4 more
2011· The Astrophysical Journal1.1Kdoi:10.1088/0004-637x/736/1/19

On 2011 February 1 the Kepler mission released data for 156,453 stars observed from the beginning of the science observations on 2009 May 2 through September 16. There are 1235 planetary candidates with transit-like signatures detected in this period. These are associated with 997 host stars. Distributions of the characteristics of the planetary candidates are separated into five class sizes: 68 candidates of approximately Earth-size ( R p < 1.25 R ⊕ ), 288 super-Earth-size (1.25 R ⊕ ⩽ R p < 2 R ⊕ ), 662 Neptune-size (2 R ⊕ ⩽ R p < 6 R ⊕ ), 165 Jupiter-size (6 R ⊕ ⩽ R p < 15 R ⊕ ), and 19 up to twice the size of Jupiter (15 R ⊕ ⩽ R p < 22 R ⊕ ). In the temperature range appropriate for the habitable zone, 54 candidates are found with sizes ranging from Earth-size to larger than that of Jupiter. Six are less than twice the size of the Earth. Over 74% of the planetary candidates are smaller than Neptune. The observed number versus size distribution of planetary candidates increases to a peak at two to three times the Earth-size and then declines inversely proportional to the area of the candidate. Our current best estimates of the intrinsic frequencies of planetary candidates, after correcting for geometric and sensitivity biases, are 5% for Earth-size candidates, 8% for super-Earth-size candidates, 18% for Neptune-size candidates, 2% for Jupiter-size candidates, and 0.1% for very large candidates; a total of 0.34 candidates per star. Multi-candidate, transiting systems are frequent; 17% of the host stars have multi-candidate systems, and 34% of all the candidates are part of multi-candidate systems.

EGRET Observations of the Diffuse Gamma‐Ray Emission from the Galactic Plane
S. D. Hunter, D. L. Bertsch, J. R. Catelli, T. M. Dame +4 more
1997· The Astrophysical Journal731doi:10.1086/304012

The high-energy diffuse gamma-ray emission from the Galactic plane, | b | ≤ 10°, is studied using observations from the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma - Ray Observatory . The spatial distribution of the diffuse emission has been determined for four broad energy ranges after removing the contribution from point sources detected with greater than 5 σ significance. The longitude and latitude distributions of the intensity, averaged over 4° latitude ranges and 10° longitude ranges, respectively, are shown for the four energy ranges. Spectra of the diffuse emission in 11 energy bands, covering the energy range 30 MeV to 30 GeV, were determined for 10° × 4° ( l × b ) bins after correcting for the finite EGRET angular resolution. The average spectrum from the direction of the inner Galaxy is shown for 29 energy bands, covering the energy range 30 MeV to 50 GeV. At latitudes | b | > 2°, corresponding to gamma rays emitted within about 3 kpc of the Sun, there is no significant variation in the spectra with Galactic longitude. Comparison of the spectra from the Galactic plane (| b | < 2°) reveals no significant variation with Galactic longitude below about 4 GeV, which suggests that the cosmic-ray electron to proton ratio does not vary significantly throughout the Galaxy. Above 4 GeV, however, there is weak (about 3 σ) evidence for variation of the Galactic plane (| b | < 2°) spectrum with longitude. The spectrum is softer in the direction of the outer Galaxy by about E compared to the spectrum from the inner Galaxy. This variation of the diffuse gamma-ray emission hints at a variation of the cosmic-ray proton spectrum with Galactic radius, which might be expected if cosmic rays are accelerated primarily in the inner Galaxy and then propagate to the outer Galaxy or if the high-energy cosmic rays are confined less well in the outer Galaxy. The spatial and spectral distributions of the diffuse emission are compared with a model calculation of this emission based on dynamic balance and realistic interstellar matter and photon distributions. The spatial comparison is used to establish the value of the molecular mass calibrating ratio N (H 2 )/ W CO and the cosmic-ray/matter coupling scale r 0 , which are the only adjustable parameters of the model. Comparisons with the observations indicates N (H 2 )/ W CO = (1.56 ± 0.05) × 10 20 mol cm -2 (K km s -1 ) -1 and r 0 = (1.76 ± 0.2) kpc. The spatial agreement between this model and the observation is very good. However, above about 1 GeV the integral intensity predicted by the model is about 60% less than the observed intensity. Although the explanation of this excess is unclear, uncertainties in the neutral pion production function or variations in the cosmic-ray spectrum with Galactic radius may partially account for the underprediction. A small medium-latitude (2° < | b | < 10°) excess in the direction of the inner Galaxy exists and may indicate that the low-energy photon density used in the model is too low.

The Evolution of L and T Dwarfs in Color‐Magnitude Diagrams
D. Saumon, Mark S. Marley
2008· The Astrophysical Journal697doi:10.1086/592734

We present new evolution sequences for very low mass stars, brown dwarfs, and giant planets and use them to explore a variety of influences on the evolution of these objects. While the predicted adiabatic evolution of luminosity with time is very similar to results of previous work, the remaining disagreements reveal the magnitude of current uncertainty in brown dwarf evolution theory. We discuss the sources of those differences and argue for the importance of the surface boundary condition provided by atmosphere models including clouds. The L- to T-type ultracool dwarf transition can be accommodated within the Ackerman and Marley cloud model by varying the cloud sedimentation parameter. We develop a simple model for the evolution across the L/T transition. By combining the evolution calculation and our atmosphere models, we generate colors and magnitudes of synthetic populations of ultracool dwarfs in the field and in Galactic clusters. We focus on near-infrared color-magnitude diagrams (CMDs) and on the nature of the "second parameter" that is responsible for the scatter of colors along the T eff sequence. Instead of a single second parameter we find that variations in metallicity and cloud parameters, unresolved binaries, and possibly a relatively young population all play a role in defining the spread of brown dwarfs along the cooling sequence. We also find that the transition from cloudy L dwarfs to cloudless T dwarfs slows down the evolution and causes a pileup of substellar objects in the transition region, in contradiction with previous studies. However, the same model is applied to the Pleiades brown dwarf sequence with less success. Taken at face value, the present Pleiades data suggest that the L/T transition occurs at lower T eff for lower gravity objects, such as those found in young Galactic clusters. The simulated populations of brown dwarfs also reveal that the phase of deuterium burning produces a distinctive feature in CMDs that should be detectable in ~50-100 Myr old clusters.

A 30-m landsat-derived cropland extent product of Australia and China using random forest machine learning algorithm on Google Earth Engine cloud computing platform
Pardhasaradhi Teluguntla, Prasad S. Thenkabail, Adam Oliphant, Jun Xiong +4 more
2018· ISPRS Journal of Photogrammetry and Remote Sensing543doi:10.1016/j.isprsjprs.2018.07.017

Mapping high resolution (30-m or better) cropland extent over very large areas such as continents or large countries or regions accurately, precisely, repeatedly, and rapidly is of great importance for addressing the global food and water security challenges. Such cropland extent products capture individual farm fields, small or large, and are crucial for developing accurate higher-level cropland products such as cropping intensities, crop types, crop watering methods (irrigated or rainfed), crop productivity, and crop water productivity. It also brings many challenges that include handling massively large data volumes, computing power, and collecting resource intensive reference training and validation data over complex geographic and political boundaries. Thereby, this study developed a precise and accurate Landsat 30-m derived cropland extent product for two very important, distinct, diverse, and large countries: Australia and China. The study used of eight bands (blue, green, red, NIR, SWIR1, SWIR2, TIR1, and NDVI) of Landsat-8 every 16-day Operational Land Imager (OLI) data for the years 2013–2015. The classification was performed by using a pixel-based supervised random forest (RF) machine learning algorithm (MLA) executed on the Google Earth Engine (GEE) cloud computing platform. Each band was time-composited over 4–6 time-periods over a year using median value for various agro-ecological zones (AEZs) of Australia and China. This resulted in a 32–48-layer mega-file data-cube (MFDC) for each of the AEZs. Reference training and validation data were gathered from: (a) field visits, (b) sub-meter to 5-m very high spatial resolution imagery (VHRI) data, and (c) ancillary sources such as from the National agriculture bureaus. Croplands versus non-croplands knowledge base for training the RF algorithm were derived from MFDC using 958 reference-training samples for Australia and 2130 reference-training samples for China. The resulting 30-m cropland extent product was assessed for accuracies using independent validation samples: 900 for Australia and 1972 for China. The 30-m cropland extent product of Australia showed an overall accuracy of 97.6% with a producer’s accuracy of 98.8% (errors of omissions = 1.2%), and user’s accuracy of 79% (errors of commissions = 21%) for the cropland class. For China, overall accuracies were 94% with a producer’s accuracy of 80% (errors of omissions = 20%), and user’s accuracy of 84.2% (errors of commissions = 15.8%) for cropland class. Total cropland areas of Australia were estimated as 35.1 million hectares and 165.2 million hectares for China. These estimates were higher by 8.6% for Australia and 3.9% for China when compared with the traditionally derived national statistics. The cropland extent product further demonstrated the ability to estimate sub-national cropland areas accurately by providing an R2 value of 0.85 when compared with province-wise cropland areas of China. The study provides a paradigm-shift on how cropland maps are produced using multi-date remote sensing. These products can be browsed at www.croplands.org and made available for download at NASA’s Land Processes Distributed Active Archive Center (LP DAAC) https://www.lpdaac.usgs.gov/node/1282.

Fast multilevel implementation of recursive spectral bisection for partitioning unstructured problems
Stephen T. Barnard, Horst D. Simon
1994· Concurrency Practice and Experience486doi:10.1002/cpe.4330060203

Abstract If problems involving unstructured meshes are to be solved efficiently on distributed‐memory parallel computers, the meshes must be partitioned and distributed across processors in a way that balances the computational load and minimizes communication. The recursive spectral bisection method (RSB) has been shown to be very effective for such partitioning problems compared to alternative methods, but RSB in its simplest form is expensive. Here a multilevel version of RSB is introduced that attains about an order‐of‐magnitude improvement in run time on typical examples.

McDonaldʼs Blood Flow in Arteries
W. W. Nichols, M. F. OʼRourke, W. Larry Kenney
1991· Journal of Cardiopulmonary Rehabilitation454doi:10.1097/00008483-199111000-00023

Lea & Febiger, 200 Chester Field Parkway, Malvern, PA 19355–9725. Laboratory for Human Performance Research The Pennsylvania State University University Park, Pennsylvania

Mapping Regional Forest Evapotranspiration and Photosynthesis by Coupling Satellite Data with Ecosystem Simulation
Steven W. Running, Ramakrishna Nemani, David L. Peterson, Larry E. Band +3 more
1989· Ecology420doi:10.2307/1941378

Annual evapotranspiration (ET) and net photosynthesis (PSN) were estimated for a mountainous 28 x 55 km region of predominantly coniferous forests in western Montana. A simple geographic information system integrated topographic, soils, vegetation, and climate data at a 1.1—km scale defined by the satellite sensor pixel size. Leaf area index (LAI) of the forest was estimated with data from the NOAA (National Oceanic and Atmospheric Administration) Advanced Very High Resolution Radiometer (AVHRR). Daily microclimate of each cell was estimated from ground and satellite data and interpolated using MT—CLIM, a mountain microclimate simulator. A forest ecosystem simulation model, Forest—BGC, was used to calculate ET and PSN daily for each cell. Ranges of estimated LAI (4—15), ET (25—60 cm/yr), and PSN (9—20 Mg°ha — 1 °yr — 1 ) across the landscape follow the trends expected in both magnitude and spatial pattern. These estimates compared well with field measurements of related variables, although absolute validation of these predictions is not possible at large spatial scales.

A unified formula for light-adapted pupil size
Andrew B. Watson, John I. Yellott
2012· Journal of Vision399doi:10.1167/12.10.12

The size of the pupil has a large effect on visual function, and pupil size depends mainly on the adapting luminance, modulated by other factors. Over the last century, a number of formulas have been proposed to describe this dependence. Here we review seven published formulas and develop a new unified formula that incorporates the effects of luminance, size of the adapting field, age of the observer, and whether one or both eyes are adapted. We provide interactive demonstrations and software implementations of the unified formula.

A generative modeling approach for benchmarking and training shallow quantum circuits
Marcello Benedetti, Delfina Garcia-Pintos, Óscar Perdomo, Vicente Leyton‐Ortega +2 more
2019· npj Quantum Information380doi:10.1038/s41534-019-0157-8

Abstract Hybrid quantum-classical algorithms provide ways to use noisy intermediate-scale quantum computers for practical applications. Expanding the portfolio of such techniques, we propose a quantum circuit learning algorithm that can be used to assist the characterization of quantum devices and to train shallow circuits for generative tasks. The procedure leverages quantum hardware capabilities to its fullest extent by using native gates and their qubit connectivity. We demonstrate that our approach can learn an optimal preparation of the Greenberger-Horne-Zeilinger states, also known as “cat states”. We further demonstrate that our approach can efficiently prepare approximate representations of coherent thermal states, wave functions that encode Boltzmann probabilities in their amplitudes. Finally, complementing proposals to characterize the power or usefulness of near-term quantum devices, such as IBM’s quantum volume, we provide a new hardware-independent metric called the qBAS score. It is based on the performance yield in a specific sampling task on one of the canonical machine learning data sets known as Bars and Stripes. We show how entanglement is a key ingredient in encoding the patterns of this data set; an ideal benchmark for testing hardware starting at four qubits and up. We provide experimental results and evaluation of this metric to probe the trade off between several architectural circuit designs and circuit depths on an ion-trap quantum computer.

Cell Death Mediated by the N-Terminal Domains of a Unique and Highly Conserved Class of NB-LRR Protein
Sarah Collier, Louis‐Philippe Hamel, Peter Moffett
2011· Molecular Plant-Microbe Interactions374doi:10.1094/mpmi-03-11-0050

Plant genomes encode large numbers of nucleotide-binding, leucine-rich repeat (NB-LRR) proteins, many of which are active in pathogen detection and defense response induction. NB-LRR proteins fall into two broad classes: those with a Toll and interleukin-1 receptor (TIR) domain at their N-terminus and those with a coiled-coil (CC) domain at the N-terminus. Within CC-NB-LRR-encoding genes, one basal clade is distinguished by having CC domains resembling the Arabidopsis thaliana RPW8 protein, which we refer to as CCR domains. Here, we show that CCR-NB-LRR-encoding genes are present in the genomes of all higher plants surveyed, and that they comprise two distinct subgroups: one typified by the Nicotiana benthamiana N-required gene 1 (NRG1) protein and the other typified by the Arabidopsis activated disease resistance gene 1 (ADR1) protein. We further report that, in contrast to CC-NB-LRR proteins, the CCR domains of both NRG1- and ADR1-like proteins are sufficient for the induction of defense responses, and that this activity appears to be SGT1-independent. Additionally, we report the apparent absence of both NRG1 homologs and TIR-NB-LRR-encoding genes from the dicot Aquilegia coerulea and the dicotyledonous order Lamiales as well as from monocotyledonous species. This strong correlation in occurrence is suggestive of a functional relationship between these two classes of NB-LRR proteins.

NASA's surface biology and geology designated observable: A perspective on surface imaging algorithms
Kerry Cawse‐Nicholson, Philip A. Townsend, David Schimel, A. Assiri +4 more
2021· Remote Sensing of Environment336doi:10.1016/j.rse.2021.112349

The 2017–2027 National Academies' Decadal Survey, Thriving on Our Changing Planet, recommended Surface Biology and Geology (SBG) as a “Designated Targeted Observable” (DO). The SBG DO is based on the need for capabilities to acquire global, high spatial resolution, visible to shortwave infrared (VSWIR; 380–2500 nm; ~30 m pixel resolution) hyperspectral (imaging spectroscopy) and multispectral midwave and thermal infrared (MWIR: 3–5 μm; TIR: 8–12 μm; ~60 m pixel resolution) measurements with sub-monthly temporal revisits over terrestrial, freshwater, and coastal marine habitats. To address the various mission design needs, an SBG Algorithms Working Group of multidisciplinary researchers has been formed to review and evaluate the algorithms applicable to the SBG DO across a wide range of Earth science disciplines, including terrestrial and aquatic ecology, atmospheric science, geology, and hydrology. Here, we summarize current state-of-the-practice VSWIR and TIR algorithms that use airborne or orbital spectral imaging observations to address the SBG DO priorities identified by the Decadal Survey: (i) terrestrial vegetation physiology, functional traits, and health; (ii) inland and coastal aquatic ecosystems physiology, functional traits, and health; (iii) snow and ice accumulation, melting, and albedo; (iv) active surface composition (eruptions, landslides, evolving landscapes, hazard risks); (v) effects of changing land use on surface energy, water, momentum, and carbon fluxes; and (vi) managing agriculture, natural habitats, water use/quality, and urban development. We review existing algorithms in the following categories: snow/ice, aquatic environments, geology, and terrestrial vegetation, and summarize the community-state-of-practice in each category. This effort synthesizes the findings of more than 130 scientists.

From thermal dissociation to condensation in the atmospheres of ultra hot Jupiters: WASP-121b in context
Vivien Parmentier, Mike R. Line, Jacob L. Bean, Megan Mansfield +4 more
2018· Astronomy and Astrophysics332doi:10.1051/0004-6361/201833059

Context. A new class of exoplanets has emerged: the ultra hot Jupiters, the hottest close-in gas giants. The majority of them have weaker-than-expected spectral features in the 1.1−1.7 μ m bandpass probed by HST/WFC3 but stronger spectral features at longer wavelengths probed by Spitzer . This led previous authors to puzzling conclusions about the thermal structures and chemical abundances of these planets. Aims. We investigate how thermal dissociation, ionization, H − opacity, and clouds shape the thermal structures and spectral properties of ultra hot Jupiters. Methods. We use the SPARC/MITgcm to model the atmospheres of four ultra hot Jupiters and discuss more thoroughly the case of WASP-121b. We expand our findings to the whole population of ultra hot Jupiters through analytical quantification of the thermal dissociation and its influence on the strength of spectral features. Results. We predict that most molecules are thermally dissociated and alkalies are ionized in the dayside photospheres of ultra hot Jupiters. This includes H 2 O , TiO, VO, and H 2 but not CO, which has a stronger molecular bond. The vertical molecular gradient created by the dissociation significantly weakens the spectral features from H 2 O while the 4.5 μ m CO feature remains unchanged. The water band in the HST/WFC3 bandpass is further weakened by the continuous opacity of the H − ions. Molecules are expected to recombine before reaching the limb, leading to order of magnitude variations of the chemical composition and cloud coverage between the limb and the dayside. Conclusions. Molecular dissociation provides a qualitative understanding of the lack of strong spectral features of water in the 1−2 μ m bandpass observed in most ultra hot Jupiters. Quantitatively, our model does not provide a satisfactory match to the WASP-121b emission spectrum. Together with WASP-33b and Kepler-33Ab, they seem the outliers among the population of ultra hot Jupiters, in need of a more thorough understanding.

<i>Kepler</i>Data Validation I—Architecture, Diagnostic Tests, and Data Products for Vetting Transiting Planet Candidates
Joseph D. Twicken, Joseph H. Catanzarite, Bruce D. Clarke, Forrest Girouard +4 more
2018· Publications of the Astronomical Society of the Pacific317doi:10.1088/1538-3873/aab694

The Kepler Mission was designed to identify and characterize transiting planets in the Kepler Field of View and to determine their occurrence rates. Emphasis was placed on identification of Earth-size planets orbiting in the Habitable Zone of their host stars. Science data were acquired for a period of four years. Long-cadence data with 29.4 min sampling were obtained for ∼200,000 individual stellar targets in at least one observing quarter in the primary Kepler Mission . Light curves for target stars are extracted in the Kepler Science Data Processing Pipeline, and are searched for transiting planet signatures. A Threshold Crossing Event is generated in the transit search for targets where the transit detection threshold is exceeded and transit consistency checks are satisfied. These targets are subjected to further scrutiny in the Data Validation (DV) component of the Pipeline. Transiting planet candidates are characterized in DV, and light curves are searched for additional planets after transit signatures are modeled and removed. A suite of diagnostic tests is performed on all candidates to aid in discrimination between genuine transiting planets and instrumental or astrophysical false positives. Data products are generated per target and planet candidate to document and display transiting planet model fit and diagnostic test results. These products are exported to the Exoplanet Archive at the NASA Exoplanet Science Institute, and are available to the community. We describe the DV architecture and diagnostic tests, and provide a brief overview of the data products. Transiting planet modeling and the search for multiple planets on individual targets are described in a companion paper. The final revision of the Kepler Pipeline code base is available to the general public through GitHub. The Kepler Pipeline has also been modified to support the Transiting Exoplanet Survey Satellite (TESS) Mission which is expected to commence in 2018.

ATMOSPHERIC SULFUR PHOTOCHEMISTRY ON HOT JUPITERS
K. Zahnle, M. S. Marley, R. S. Freedman, K. Lodders +1 more
2009· The Astrophysical Journal304doi:10.1088/0004-637x/701/1/l20

We develop a new one-dimensional photochemical kinetics code to address stratospheric chemistry and stratospheric heating in hot Jupiters. Here we address optically active S-containing species and CO 2 at 1200 ⩽ T ⩽ 2000 K. HS (mercapto) and S 2 are highly reactive species that are generated photochemically and thermochemically from H 2 S with peak abundances between 1 and 10 mbar. S 2 absorbs UV between 240 and 340 nm and is optically thick for metallicities [S/H]>0 at T ⩾ 1200 K. HS is probably more important than S 2 , as it is generally more abundant than S 2 under hot Jupiter conditions and it absorbs at somewhat redder wavelengths. We use molecular theory to compute an HS absorption spectrum from sparse available data and find that HS should absorb strongly between 300 and 460 nm, with absorption at the longer wavelengths being temperature sensitive. When the two absorbers are combined, radiative heating (per kg of gas) peaks at 100 μbars, with a total stratospheric heating of ∼8 × 10 4 W m −2 for a jovian planet orbiting a solar-twin at 0.032 AU. Total heating is insensitive to metallicity. The CO 2 mixing ratio is a well behaved quadratic function of metallicity, ranging from 1.6 × 10 −8 to 1.6 × 10 −4 for −0.3 < [M/H] < 1.7. CO 2 is insensitive to insolation, vertical mixing, temperature (1200 < T < 2000), and gravity. The photochemical calculations confirm that CO 2 should prove a useful probe of planetary metallicity.

CHEMICAL CONSEQUENCES OF THE C/O RATIO ON HOT JUPITERS: EXAMPLES FROM WASP-12b, CoRoT-2b, XO-1b, AND HD 189733b
Julianne I. Moses, Nikku Madhusudhan, Channon Visscher, Richard Freedman
2012· The Astrophysical Journal297doi:10.1088/0004-637x/763/1/25

Motivated by recent spectroscopic evidence for carbon-rich atmospheres on some transiting exoplanets, we investigate the influence of the C/O ratio on the chemistry, composition, and spectra of extrasolar giant planets both from a thermochemical equilibrium perspective and from consideration of disequilibrium processes like photochemistry and transport-induced quenching. We find that although CO is predicted to be a major atmospheric constituent on hot Jupiters for all C/O ratios, other oxygen-bearing molecules like H 2 O and CO 2 are much more abundant when C/O < 1, whereas CH 4 , HCN, and C 2 H 2 gain significantly in abundance when C/O > 1. Other notable species like N 2 and NH 3 that do not contain carbon or oxygen are relatively unaffected by the C/O ratio. Disequilibrium processes tend to enhance the abundance of CH 4 , NH 3 , HCN, and C 2 H 2 over a wide range of C/O ratios. We compare the results of our models with secondary-eclipse photometric data from the Spitzer Space Telescope and conclude that (1) disequilibrium models with C/O ∼ 1 are consistent with spectra of WASP-12b, XO-1b, and CoRoT-2b, confirming the possible carbon-rich nature of these planets; (2) spectra from HD 189733b are consistent with C/O ≲ 1, but as the assumed metallicity is increased above solar, the required C/O ratio must increase toward 1 to prevent too much H 2 O absorption; (3) species like HCN can have a significant influence on spectral behavior in the 3.6 and 8.0 μm Spitzer channels, potentially providing even more opacity than CH 4 when C/O > 1; and (4) the very high CO 2 abundance inferred for HD 189733b from near-infrared observations cannot be explained through equilibrium or disequilibrium chemistry in a hydrogen-dominated atmosphere. We discuss possible formation mechanisms for carbon-rich hot Jupiters, including scenarios in which the accretion of CO-rich, H 2 O-poor gas dominates the atmospheric envelope, and scenarios in which the planets accrete carbon-rich solids while migrating through disk regions inward of the snow line. The C/O ratio and bulk atmospheric metallicity provide important clues regarding the formation and evolution of the giant planets.

MASSES, RADII, AND CLOUD PROPERTIES OF THE HR 8799 PLANETS
Mark S. Marley, D. Saumon, Michael C. Cushing, Andrew S. Ackerman +2 more
2012· The Astrophysical Journal291doi:10.1088/0004-637x/754/2/135

The near-infrared colors of the planets directly imaged around the A star HR 8799 are much redder than most field brown dwarfs of the same effective temperature. Previous theoretical studies of these objects have concluded that the atmospheres of planets b, c, and d are unusually cloudy or have unusual cloud properties. Some studies have also found that the inferred radii of some or all of the planets disagree with expectations of standard giant planet evolution models. Here, we compare the available data to the predictions of our own set of atmospheric and evolution models that have been extensively tested against observations of field L and T dwarfs, including the reddest L dwarfs. Unlike some previous studies, we require mutually consistent choices for effective temperature, gravity, cloud properties, and planetary radius. This procedure thus yields plausible values for the masses, effective temperatures, and cloud properties of all three planets. We find that the cloud properties of the HR 8799 planets are not unusual but rather follow previously recognized trends, including a gravity dependence on the temperature of the L to T spectral transition—some reasons for which we discuss. We find that the inferred mass of planet b is highly sensitive to whether or not we include the H - and the K -band spectrum in our analysis. Solutions for planets c and d are consistent with the generally accepted constraints on the age of the primary star and orbital dynamics. We also confirm that, like in L and T dwarfs and solar system giant planets, non-equilibrium chemistry driven by atmospheric mixing is also important for these objects. Given the preponderance of data suggesting that the L to T spectral type transition is gravity dependent, we present an exploratory evolution calculation that accounts for this effect. Finally we recompute the bolometric luminosity of all three planets.

COSMOS-Web: An Overview of the JWST Cosmic Origins Survey
Caitlin M. Casey, Jeyhan S. Kartaltepe, Nicole E. Drakos, Maximilien Franco +4 more
2023· The Astrophysical Journal287doi:10.3847/1538-4357/acc2bc

Abstract We present the survey design, implementation, and outlook for COSMOS-Web, a 255 hr treasury program conducted by the James Webb Space Telescope in its first cycle of observations. COSMOS-Web is a contiguous 0.54 deg 2 NIRCam imaging survey in four filters (F115W, F150W, F277W, and F444W) that will reach 5 σ point-source depths ranging ∼27.5–28.2 mag. In parallel, we will obtain 0.19 deg 2 of MIRI imaging in one filter (F770W) reaching 5 σ point-source depths of ∼25.3–26.0 mag. COSMOS-Web will build on the rich heritage of multiwavelength observations and data products available in the COSMOS field. The design of COSMOS-Web is motivated by three primary science goals: (1) to discover thousands of galaxies in the Epoch of Reionization (6 ≲ z ≲ 11) and map reionization’s spatial distribution, environments, and drivers on scales sufficiently large to mitigate cosmic variance, (2) to identify hundreds of rare quiescent galaxies at z &gt; 4 and place constraints on the formation of the universe’s most-massive galaxies ( M ⋆ &gt; 10 10 M ⊙ ), and (3) directly measure the evolution of the stellar-mass-to-halo-mass relation using weak gravitational lensing out to z ∼ 2.5 and measure its variance with galaxies’ star formation histories and morphologies. In addition, we anticipate COSMOS-Web’s legacy value to reach far beyond these scientific goals, touching many other areas of astrophysics, such as the identification of the first direct collapse black hole candidates, ultracool subdwarf stars in the Galactic halo, and possibly the identification of z &gt; 10 pair-instability supernovae. In this paper we provide an overview of the survey’s key measurements, specifications, goals, and prospects for new discovery.