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1. Time Evolution Images of the Hypergiant RW Cephei during the Rebrightening Phase Following the Great Dimming

Author: Narsireddy Anugu, Douglas R. Gies, Rachael M. Roettenbacher, John D. Monnier, Miguel Montargés, Antoine Mérand, Fabien Baron, Gail H. Schaefer, Katherine A. Shepard, Stefan Kraus, Matthew D. Anderson, Isabelle Codron, Tyler Gardner, Mayra Gutierrez, Rainer Köhler, Karolina Kubiak, Cyprien Lanthermann, Olli Majoinen, Nicholas J. Scott, and Wolfgang Vollmann
Subjects: Late-type supergiant stars, Stellar mass loss, Stellar radii, Long period variable stars, Yellow hypergiant stars, Hypergiant stars, Astrophysics, QB460-466
Abstract: Stars with initial masses larger than 8 M _⊙ undergo substantial mass loss through mechanisms that remain elusive. Unraveling the origins of this mass loss is important for comprehending the evolutionary path of these stars, the type of supernova explosion, and whether they become neutron stars or black hole remnants. In 2022 December, RW Cep experienced the Great Dimming in its visible brightness, presenting a unique opportunity to understand mass-loss mechanisms. Our previous observations of RW Cep from the CHARA Array, taken during the dimming phase, show a compelling asymmetry in the star images, with a darker zone on the west side of the star indicating the presence of dust in front of the star in our line of sight. Here, we present multiepoch observations from CHARA while the star rebrightened in 2023. We created images using three image reconstruction methods and an analytical model fit. Comparisons of images acquired during the dimming and rebrightening phases reveal remarkable differences. Specifically, the west side of RW Cep, initially obscured during the dimming phase, reappeared during the subsequent rebrightening phase, and the measured angular diameter became larger by 8%. We also observed image changes from epoch to epoch while the star is brightening, indicating the time evolution of dust in front of the star. We suggest that the dimming of RW Cep was a result of a recent surface mass ejection event, generating a dust cloud that partially obstructed the stellar photosphere.
Published: 2024
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2. The Orbit and Dynamical Mass of Polaris: Observations with the CHARA Array

Author: Nancy Remage Evans, Gail H. Schaefer, Alexandre Gallenne, Guillermo Torres, Elliott P. Horch, Richard I. Anderson, John D. Monnier, Rachael M. Roettenbacher, Fabien Baron, Narsireddy Anugu, James W. Davidson Jr., Pierre Kervella, Garance Bras, Charles Proffitt, Antoine Mérand, Margarita Karovska, Jeremy Jones, Cyprien Lanthermann, Stefan Kraus, Isabelle Codron, Howard E. Bond, and Giordano Viviani
Subjects: Cepheid variable stars, Stellar masses, Astrophysics, QB460-466
Abstract: The 30 yr orbit of the Cepheid Polaris has been followed with observations by the Center for High Angular Resolution Astronomy (CHARA) Array from 2016 through 2021. An additional measurement has been made with speckle interferometry at the Apache Point Observatory. Detection of the companion is complicated by its comparative faintness—an extreme flux ratio. Angular diameter measurements appear to show some variation with pulsation phase. Astrometric positions of the companion were measured with a custom grid-based model-fitting procedure and confirmed with the CANDID software. These positions were combined with the extensive radial velocities (RVs) discussed by Torres to fit an orbit. Because of the imbalance of the sizes of the astrometry and RV data sets, several methods of weighting are discussed. The resulting mass of the Cepheid is 5.13 ± 0.28 M _⊙ . Because of the comparatively large eccentricity of the orbit (0.63), the mass derived is sensitive to the value found for the eccentricity. The mass combined with the distance shows that the Cepheid is more luminous than predicted for this mass from evolutionary tracks. The identification of surface spots is discussed. This would give credence to the identification of a radial velocity variation with a period of approximately 120 days as a rotation period. Polaris has some unusual properties (rapid period change, a phase jump, variable amplitude, and unusual polarization). However, a pulsation scenario involving pulsation mode, orbital periastron passage, and low pulsation amplitude can explain these characteristics within the framework of pulsation seen in Cepheids.
Published: 2024
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3. CHARA Near-infrared Imaging of the Yellow Hypergiant Star ρ Cassiopeiae: Convection Cells and Circumstellar Envelope

Author: Narsireddy Anugu, Fabien Baron, John D. Monnier, Douglas R. Gies, Rachael M. Roettenbacher, Gail H. Schaefer, Miguel Montargès, Stefan Kraus, Jean-Baptiste Le Bouquin, Matthew D. Anderson, Theo ten Brummelaar, Isabelle Codron, Christopher D. Farrington, Tyler Gardner, Mayra Gutierrez, Rainer Köhler, Cyprien Lanthermann, Ryan Norris, Nicholas J. Scott, Benjamin R. Setterholm, and Norman L. Vargas
Subjects: Late-type supergiant stars, Stellar mass loss, Stellar radii, Variable stars, Long period variable stars, Astrophysics, QB460-466
Abstract: Massive evolved stars such as red supergiants and hypergiants are potential progenitors of Type II supernovae, and they are known for ejecting substantial amounts of matter, up to half their initial mass, during their final evolutionary phases. The rate and mechanism of this mass loss play a crucial role in determining their ultimate fate and the likelihood of their progression to supernovae. However, the exact mechanisms driving this mass ejection have long been a subject of research. Recent observations, such as the Great Dimming of Betelgeuse, have suggested that the activity of large convective cells, combined with pulsation, could be a plausible explanation for such mass-loss events. In this context, we conducted interferometric observations of the famous yellow hypergiant, ρ Cassiopeiae using the CHARA Array in H- and K -band wavelengths. ρ Cas is well known for its recurrent eruptions, characterized by periods of visual dimming (∼1.5–2 mag) followed by recovery. From our observations, we derived the diameter of the limb-darkened disk and found that this star has a radius of 1.04 ± 0.01 mas, or 564–700 R _⊙ . We performed image reconstructions with three different image reconstruction software packages, and they unveiled the presence of giant hot and cold spots on the stellar surface. We interpret these prominent hot spots as giant convection cells, suggesting a possible connection to mass ejections from the star’s envelope. Furthermore, we detected spectral CO emission lines in the K band ( λ = 2.31–2.38 μ m), and the image reconstructions in these spectral lines revealed an extended circumstellar envelope with a radius of 1.45 ± 0.10 mas.
Published: 2024
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4. Geodynamic seawater-sediment porewater evolution of the east central Atlantic Paleogene ocean margin revealed by U-Pb dating of sedimentary phosphates

Author: Jérémie Aubineau, Fleurice Parat, Ernest Chi Fru, Radouan El Bamiki, Olivia Mauguin, Fabien Baron, Marc Poujol, and Michel Séranne
Subjects: carbonate fluorapatite, in situ U-Pb dating, Moroccan High Atlas, Paleogene, seawater signature, Science
Abstract: Emerging evidence suggests that U-Pb and Lu-Hf ages of sedimentary apatite group minerals are often younger than their biostratigraphic ages. However, U-Pb dating of exquisitely preserved carbonate fluorapatite (CFA) is rare. The Upper Cretaceous/Paleogene marine sedimentary rocks of the Moroccan High Atlas host phosphate-rich sediments bracketed by calcareous nannofossil Zones (NP4-NP9) of late Danian to Thanetian age. Here, we use a laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to decipher whether CFA minerals are suitable for U-Pb chronostratigraphy and whether they can reveal the sedimentary and seawater history from which they formed. U-Pb dating of the CFA grains yields ages of 42.9 ± 1.3 Ma (MSWD = 2.3) and 35.7 ± 2.8 Ma (MSWD = 1.3) from three distinct phosphate-rich beds, being >15 million years younger than the expected biostratigraphic age. Combined scanning electron microscopy, X-ray diffraction, and infrared spectroscopy analyses, associate the Mg-rich clay minerals sepiolite and palygorskite, with micro-CFA crystals, while LA-ICP-MS trace element, rare earth element, and yttrium content for primary CFA grains, collectively point to long-term early diagenetic adsorption from oxygenated seawater-dominated porewater fluids. Authigenic clay minerals display a seawater-like pattern, with negligible U concentrations suggesting limited clay mineral influence on U-Pb dating of the CFA crystals. Considering the absence of extensive post-depositional alteration, we propose that because of their large surface area, the µm-sized CFA crystallites facilitated real-time surface adsorption and desorption of elements and diffusion processes. These conditions generated long-term open system connection of sediments with overlying seawater, enabling continuous U-Pb exchange for 15–25 Myr after phosphate precipitation. The data suggest that system closure was potentially associated with sediment lithification and the Atlas orogeny, pointing to stable oxygenation of shallow marine waters along the eastern passive margin of the central Atlantic Ocean in the Paleogene.
Published: 2022
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5. A multiparametric study on the dissolution of synthetic brannerite

Author: Hantao Lin, Stéphanie Szenknect, Adel Mesbah, Fabien Baron, Daniel Beaufort, Yann Batonneau, Julien Mercadier, Aurélien Eglinger, Marion Turuani, Anne-Magali Seydoux-Guillaume, Philippe Goncalves, Flavien Choulet, Virginie Chapon, Maurice Pagel, and Nicolas Dacheux
Subjects: Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract: Abstract Brannerite, UTi2O6 is reported to occur in various uraniferous deposits worldwide. Natural brannerite specimens are found in the amorphous state and are usually considered to be refractory to dissolution due to the formation of TiO2 passivation layer. In the present work, brannerite was synthesized by wet chemistry route, then characterized prior the development of multiparametric dissolution experiments. The evolution of U and Ti concentrations was followed in 0.1–2 mol/L H2SO4 solutions, for temperatures ranging from 25 to 80 °C, in the presence (or not) of 2.8 g/L of dissolved Fe(III). The dissolution of synthetic brannerite was congruent in the whole experimental domain. The formation of Ti-enriched secondary phase at the surface of the brannerite grains was not evidenced. The dissolution rate constants, activation energies and partial orders of the overall dissolution reaction relative to proton activity were determined in the presence (or absence) of Fe(III). The introduction of Fe(III) in sulfuric acid solutions increased the dissolution rate constant by 5 orders of magnitude and induced significant modifications of the apparent activation energy (from 71 ± 4 to 91 ± 6 kJ/mol) and of the partial order relative to proton activity (from 0.42 ± 0.09 to 0.84 ± 0.08). This study suggested that the uncongruency of the brannerite dissolution and the changes usually observed in the rate-controlling step with temperature could be linked to the loss of the crystal structure in natural samples.
Published: 2021
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6. The Great Dimming of the Hypergiant Star RW Cephei: CHARA Array Images and Spectral Analysis

Author: Narsireddy Anugu, Fabien Baron, Douglas R. Gies, Cyprien Lanthermann, Gail H. Schaefer, Katherine A. Shepard, Theo ten Brummelaar, John D. Monnier, Stefan Kraus, Jean-Baptiste Le Bouquin, Claire L. Davies, Jacob Ennis, Tyler Gardner, Aaron Labdon, Rachael M. Roettenbacher, Benjamin R. Setterholm, Wolfgang Vollmann, and Costantino Sigismondi
Subjects: Late-type supergiant stars, Stellar mass loss, Stellar radii, Variable stars, Astronomy, QB1-991
Abstract: The cool hypergiant star RW Cephei is currently in a deep photometric minimum that began several years ago. This event bears a strong similarity to the Great Dimming of the red supergiant Betelgeuse that occurred in 2019–2020. We present the first resolved images of RW Cephei that we obtained with the CHARA Array interferometer. The angular diameter and Gaia distance estimates indicate a stellar radius of 900–1760 R _⊙ , which makes RW Cephei one of the largest stars known in the Milky Way. The reconstructed, near-infrared images show a striking asymmetry in the disk illumination with a bright patch offset from the center and a darker zone to the west. The imaging results depend on assumptions made about the extended flux, and we present two cases with and without allowing extended emission. We also present a recent near-infrared spectrum of RW Cep that demonstrates that the fading is much larger at visual wavelengths compared to that at near-infrared wavelengths as expected for extinction by dust. We suggest that the star’s dimming is the result of a recent surface mass ejection event that created a dust cloud that now partially blocks the stellar photosphere.
Published: 2023
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7. Imaging the Inner Astronomical Unit of the Herbig Be Star HD 190073

Author: Nour Ibrahim, John D. Monnier, Stefan Kraus, Jean-Baptiste Le Bouquin, Narsireddy Anugu, Fabien Baron, Theo Ten Brummelaar, Claire L. Davies, Jacob Ennis, Tyler Gardner, Aaron Labdon, Cyprien Lanthermann, Antoine Mérand, Evan Rich, Gail H. Schaefer, and Benjamin R. Setterholm
Subjects: Young stellar objects, Herbig Ae/Be stars, Protoplanetary disks, Long baseline interferometry, Astrophysics, QB460-466
Abstract: The inner regions of protoplanetary disks host many complex physical processes such as star–disk interactions, magnetic fields, planet formation, and the migration of new planets. To study directly this region requires milliarcsecond angular resolution, beyond the diffraction limit of the world's largest optical telescopes and even too small for the millimeter-wave interferometer Atacama Large Millimeter/submillimeter Array (ALMA). However, we can use infrared interferometers to image the inner astronomical unit. Here, we present new results from the CHARA and VLTI arrays for the young and luminous Herbig Be star HD 190073. We detect a sub-astronomical unit (sub-AU) cavity surrounded by a ring-like structure that we interpret as the dust destruction front. We model the shape with six radial profiles, three symmetric and three asymmetric, and present a model-free image reconstruction. All the models are consistent with a near face-on disk with an inclination ≲20°, and we measure an average ring radius of 1.4 ± 0.2 mas (1.14 au). Around 48% of the total flux comes from the disk with 15% of that emission appearing to emerge from inside the inner rim. The cause of emission is still unclear, perhaps due to different dust grain compositions or gas emission. The skewed models and the imaging point to an off-center star, possibly due to binarity. Our image shows sub-AU structure, which seems to move between the two epochs inconsistently with Keplerian motion and we discuss possible explanations for this apparent change.
Published: 2023
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8. Gas Chromatography Fingerprint of Martian Amino Acids before Analysis of Return Samples

Author: Rihab Fkiri, Ramzi Timoumi, Guillaume Rioland, Pauline Poinot, Fabien Baron, Brian Gregoire, and Claude Geffroy-Rodier
Subjects: gas chromatography, amino acids, derivatization, extraction, sensor, Biochemistry, QD415-436
Abstract: Within the perspective of the current and future space missions, the detection and separation of building blocks such as amino acids are important subjects which are becoming fundamental in the search for the origin of life and traces of life in the solar system. In this work, we have developed and optimized a strategy adapted to space experimentation to detect the presence of amino acid-like compounds using gas chromatography coupled to mass spectrometry (GC-MS). Selected derivatization methods meet the instrument design constraints imposed on in situ extraterrestrial experiments. Coupled to a fast selective extraction, GC analysis would be highly efficient for the detection of organic materials. In the future, the corresponding GC-MS TIC could facilitate simple and fast selection of sediments/dust samples onboard GC-MS-equipped rovers for sample return-to-Earth missions.
Published: 2023
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9. How do repeated redox cycles affect the tetrahedrally coordinated iron and influence the mineralogy and redox properties of iron-rich clay minerals?

Author: Thomas B Hofstetter, Anke Neumann, Carolyn Pearce, Meret Aeppli, Fabien Baron, and Jagannath Biswakarma
Published: 2023
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10. Imaging the inner astronomical unit of Herbig Be star HD 190073

Author: Nour Ibrahim, John D. Monnier, Stefan Kraus, Jean-Baptiste Le Bouquin, Narsireddy Anugu, Fabien Baron, Theo Ten Brummelaar, Claire L. Davies, Jacob Ennis, Tyler Gardner, Aaron Labdon, Cyprien Lanthermann, Antoine Mérand, Evan Rich, Gail H. Schaefer, and Benjamin R. Setterholm
Subjects: Earth and Planetary Astrophysics (astro-ph.EP), Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics - Earth and Planetary Astrophysics
Abstract: Inner regions of protoplanetary disks host many complex physical processes such as star-disk interactions, magnetic fields, planet formation, and the migration of new planets. To directly study this region requires milli-arcsecond angular resolution, beyond the diffraction limit of the world's largest optical telescopes and even too small for the mm-wave interferometer ALMA. However, we can use infrared interferometers to image the inner astronomical unit. Here, we present new results from the CHARA and VLTI arrays for the young and luminous Herbig Be star HD 190073. We detect a sub-AU cavity surrounded by a ring-like structure that we interpret as the dust destruction front. We model the shape with 6 radial profiles, 3 symmetric and 3 asymmetric, and present a model-free image reconstruction. All the models are consistent with a near face-on disk with inclination $\lesssim 20^\circ$, and we measure an average ring radius of 1.4 $\pm 0.2$ mas (1.14 AU). Around $48\%$ of the total flux comes from the disk with ~$15\%$ of that emission appearing to emerge from inside the inner rim. The cause of emission is still unclear, perhaps due to different dust grain compositions or gas emission. The skewed models and the imaging point to an off-center star, possibly due to binarity. Our image shows a sub-AU structure, which seems to move between the two epochs inconsistently with Keplerian motion and we discuss possible explanations for this apparent change., Comment: 20 pages, 9 figures
Published: 2023
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11. The Future of Exoplanet Direct Detection

Author: John Monnier, Gioia Rau, Ellyn K Baines, Joel Sanchez‐Bermudez, Martin Elvis, Sam Ragland, Rachel L Akeson, Gerard van Belle, Ryan Norris, Kathryn Gordon, Denis Defrère, Stephen Ridgway, Jean‐Baptiste Le Bouquin, Narsireddy Anugu, Nicholas Scott, Stephen Kane, Noel Richardson, Zsolt Regal, Zhaohuan Zhu, Andrea Chiavassa, Gautam Vasisht, Keivan G Stassun, Chuanfei Dong, Olivier Absi, Sylvestre Lacour, Gerd Weigelt, Douglas Gies, Fred C Adams, Nuria Calvet, Sascha P. Quanz, Catherine Espaillat, Tyler Gardner, Alexandra Greenbaum, Rafael Millan‐Gabet, Chris Packham, Mario Gai, Quentin Kral, Jean‐Philippe Berger, Hendrik Linz, Lucia Klarmann, Jaehan Bae, Rebeca Garcia Lopez, Gallenne Alexandre, Fabien Baron, Lee Hartmann, Makoto Kishimoto, Melissa McClure, Johan Olofsson, Chris Haniff, Michael Line, Romain G. Petrov, Michael Smith, Christian Hummel, Theo ten Brummelaar, Matthew De Furio, Stephen Rinehart, David Leisawitz, William Danchi, Daniel Huber, Edward Wishnow, Denis Mourard, Benjamin Pope, Michael Ireland, Stefan Kraus, Benjamin Setterholm, and Russel White
Subjects: Instrumentation And Photography
Abstract: Diffraction fundamentally limits our ability to image and characterize exoplanets. Currant and planned coronagraphic searches for exoplanets are making incredible strides but are fundamentally limited by the inner working angle of a few λ/D. Some crucial topics, such as demographics of exoplanets within the first 50 Myr and the infrared characterization of terrestrial planets, are beyond the reach of the single aperture angular resolution for the foreseeable future. Interferometry offers some advantages in exoplanet detection and characterization and we explore in this white paper some of the potential scientific breakthroughs possible. We demonstrate here that investments in "exoplanet interferometry" could open up new possibilities for speckle suppression through spatial coherence, a giant boost in astrometric precision for determining exoplanet orbits, ability to take a census of young giant exoplanets (clusters <50 Myr age), and an unrivaled potential for infrared nulling from space to detect terrestrial planets and search for atmospheric biomarkers. All signs point to an exciting future for exoplanets and interferometers, albeit a promise that will take decades to fulfill.
Published: 2019

12. Imaging the Key Stages of Planet Formation

Author: John Monnier, Gioia Rau, Joel Sanchez‐Bermudez, Sam Ragland, Rachel Akeson, Gerard van Belle, Ryan Norris, Kathryn Gordon, Denis Defrère, Jacques Kluska, Stephen Ridgway, Jean‐Baptiste Le Bouquin, Narsireddy Anugu, Nicholas Sco, Stephen Kane, Noel D Richardson, Zsolt Regaly, Zhaohuan Zhu, Gautam Vasisht, Keivan G. Stassun, Sean Andrews, Sylvestre Lacour, Gerd Weigelt, Neal Turner, Fred C Adams, Douglas Gies, Nuria Calvet, Catherine Espaillat, Rafael Millan‐Gabet, Tyler Gardner, Chris Packham, Mario Gai, Quentin Kral, Jean‐Philippe Berger, Hendrik Linz, Lucia Klarmann, Matthew Bate, Jaehan Bae, Rebeca Garcia Lopez, Antonio Garufi, Fabien Baron, Mihkel Kama, David Wilner, Lee Hartmann, Makoto Kishimoto, Johan Olofsson, Melissa McClure, Chris Haniff, Sebastian Hoenig, Michael Line, Romain G. Petrov, Michael Smith, Theo ten Brummelaar, Matthew De Furio, Maria Koutoulaki, Stephen Rinehart, David Leisawitz, William C Danchi, Daniel Huber, Ke Zhang, Benjamin Pope, Michael Ireland, Stefan Kraus, Andrea Isella, Benjamin Setterholm, and Russel White
Subjects: Astronomy
Abstract: New images of young stars are revolutionizing our understanding of planet formation. ALMA detects large grains in planet‐forming disks with few AU scale resolution and scattered light imaging with extreme adaptive optics systems reveal small grains suspended on the disks’ flared surfaces. Tantalizing evidence for young exoplanets is emerging from line observations of CO and H‐alpha. In this white paper, we explore how even higher angular resolution can extend our understanding of the key stages of planet formation, to resolve accreting circumplanetary disks themselves, and to watch planets forming in situ for the nearest star‐forming regions. We focus on infrared observations which are sensitive to thermal emission in the terrestrial planet formation zone and allow access to molecular tracers in warm ro‐vibrational states. Successful planet formation theories will not only be able to explain the diverse features seen in disks, but will also be consistent with the rich exoplanet demographics from RV and transit surveys. While we are far from exhausting ground‐based techniques, the ultimate combination of high angular resolution and high infrared sensitivity can only be achieved through mid‐infrared space interferometry.
Published: 2019

13. High Angular Resolution Astrophysics: Resolving Stellar Surface Features

Author: Rachael M. Roettenbacher, Ryan P. Norris, Fabien Baron, Kenneth G Carpenter, Michelle J. Creech-Eakman, Douglas Gies, Thomas Maccarone, John D. Monnier, Gioia Rau, Stephen Ridgway, Gail H. Schaefer, and Theo ten Brummelaar
Subjects: Astronomy
Abstract: We are now in an era where we can image details on the surfaces of stars. When resolving stellar surfaces, we see that every surface is uniquely complicated. Each imaged star provides insight into not only the stellar surface structures, but also the stellar interiors suggesting constraints on evolution and dynamo models. As more resources become operational in the coming years, imaging stellar surfaces should become commonplace for revealing the true nature of stars. Here, we discuss the main types of stars for which imaging surface features is currently useful and what improved observing techniques would provide for imaging stellar surface features.
Published: 2019

14. Authigenic kaolinite and sudoite in sandstones from the Paleoproterozoic Franceville sub-basin (Gabon)

Author: Olabode M. Bankole, Brian Grégoire, Fabien Baron, Abderrazak El Albani, and Jérémie Aubineau
Subjects: Geochemistry, General Earth and Planetary Sciences, Kaolinite, Authigenic, Structural basin, Geology, General Environmental Science
Published: 2021
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15. First-principles modeling of the infrared spectrum of Fe- and Al-bearing lizardite

Author: Fabien Baron, Sabine Petit, Farid Juillot, Etienne Balan, Guillaume Radtke, Lorenzo Paulatto, Emmanuel Fritsch, Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD [Nouvelle-Calédonie]), Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), and Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Materials science, 010504 meteorology & atmospheric sciences, Absorption spectroscopy, Infrared, Mineralogy, 010502 geochemistry & geophysics, 01 natural sciences, Spectral line, Ion, Crystallography, TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES, Octahedron, Impurity, Supercell (crystal), Density functional theory, QE351-399.2, 0105 earth and related environmental sciences, [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
Abstract: The theoretical vibrational properties of a series of Fe- and Al-bearing lizardite models have been determined at the density functional theory level. Each periodic model displays a single cationic impurity substituted at an octahedral or tetrahedral site of a supercell of lizardite (Mg3Si2O5(OH)4) containing 162 atoms. The isovalent Fe2+ for Mg2+ substitution has been considered, as well as the heterovalent substitution of Fe3+ or Al3+ for Mg2+ or Si4+. Comparison of the theoretical absorption spectra with previously reported experimental spectra of natural and laboratory-grown lizardite samples allows us to propose an interpretation for most of the observed bands. Although the identification of specific bands related to octahedral Fe2+ in FTIR spectra is challenging, broad bands at 3584 and 3566 cm−1 reflect the occurrence of octahedral Al3+ and Fe3+, respectively, in the natural samples. These broad bands likely overlap with potential contribution related to tetrahedral Al3+. It is suggested that the modification of the H-bonding pattern related to the incorporation of trivalent ions at tetrahedral sites has an overall broadening effect on the interlayer-OH stretching bands of lizardite.
Published: 2021
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16. Controls on tetrahedral Fe(III) abundance in 2:1 phyllosilicates—Discussion

Author: Alain Decarreau, Fabien Baron, Sabine Petit, Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), and Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Chemistry, 2:1 phyllosilicates, smectite, 020101 civil engineering, Nontronite, 02 engineering and technology, 010502 geochemistry & geophysics, partition coefficient, 01 natural sciences, 0201 civil engineering, Partition coefficient, Crystallography, tetrahedral Fe, Geophysics, Geochemistry and Petrology, Abundance (ecology), [SDU]Sciences of the Universe [physics], Tetrahedron, nontronite, Clay minerals, 0105 earth and related environmental sciences
Abstract: Cuadros et al. (2019) used a wide range of data from dioctahedral and trioctahedral Fe3+-bearing, 2:1 phyllosilicates to propose a model describing how tetrahedral occupancy by Fe3+ takes place in both dioctahedral and trioctahedral 2:1 phyllosilicates. The partition coefficient approach (Decarreau and Petit 2014) focusing on the distribution of Al3+ and Fe3+ between octahedral and tetrahedral sites of dioctahedral smectites has been disregarded in the study of Cuadros et al. (2019). This approach was applied here on the set of data from Cuadros et al. (2019). The partition coefficient value linked to the distribution of Al3+ and Fe3+ between octahedral and tetrahedral sites determined from natural and synthetic dioctahedral smectites applies well to trioctahedral phyllosilicates too. Data from synthetic iron-rich 2:1 smectites also fit well with both Cuadros et al. (2019) and Decarreau and Petit (2014) models.
Published: 2021
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17. Crystal Growth of Smectite: A Study Based on the Change in Crystal Chemistry and Morphology of Saponites with Synthesis Time

Author: Hongping He, Fabien Baron, Angelina Razafitianamaharavo, Sabine Petit, Jianxi Zhu, Frédéric Villiéras, Qi Tao, Chaoqun Zhang, Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Chinese Institutions of Earth Science, Chinese Academy of Sciences [Beijing] (CAS), Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC), Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Terre et Environnement de Lorraine (OTELo), and Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, Morphology (linguistics), Materials science, Crystal chemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Crystal growth, 02 engineering and technology, 010502 geochemistry & geophysics, 01 natural sciences, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Geochemistry and Petrology, medicine, [CHIM]Chemical Sciences, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Crust, 021001 nanoscience & nanotechnology, Chemical engineering, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Swelling, medicine.symptom, 0210 nano-technology, Clay minerals, Earth (classical element), [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
Abstract: Smectites are 2:1 type swelling clay minerals widely distributed in the earth’s crust. The unique structures and properties endow them with various applications in many fields. However, their growt...
Published: 2019
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18. Experimental evidence of the metastability of ferric smectite

Author: Alain Decarreau, Sabine Petit, Fabien Baron, Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), and Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: synthesis, 010504 meteorology & atmospheric sciences, 010502 geochemistry & geophysics, thermodynamic equilibrium, 01 natural sciences, law.invention, Geochemistry and Petrology, law, medicine, [CHIM]Chemical Sciences, nontronite, Crystallization, Dissolution, 0105 earth and related environmental sciences, Chemistry, nanoparticle, Nontronite, Aegirine, Hematite, clay minerals, Chemical engineering, [SDU]Sciences of the Universe [physics], 13. Climate action, visual_art, [SDE]Environmental Sciences, smectite metastability, visual_art.visual_art_medium, Ferric, Chemical stability, Clay minerals, medicine.drug
Abstract: International audience; The stability of clay minerals, and especially ferric smectites, as a function of time, is of interest for natural environments due to their high capacity to exchange electrons that control a large part of the geochemical cycle of different redox-sensitive organic or inorganic compounds (e.g., elements, nutrients, pollutants). An experimental approach based on hydrothermal synthesis was performed for synthesizing two series of iron-rich smectite (Na-nontronite) at two pH (near 12 and 13) from 1 day to several months at 150 °C. XRD, FTIR, and HRTEM data of the synthetic products confirmed the formation of Na-nontronite for the short time duration experiments. However, the dissolution of Na-nontronite and the concomitant formation of aegirine were observed with the increase of synthesis time. The pH of crystallization fluids clearly influences the rate of the reactions. At highest pH, Na-nontronite disappeared totally after two months and aegirine and hematite were the only crystalline phases observed. The chemical compositions of solutions were over time far from the thermodynamic stability field of nontronite, but very close to that of the aegirine-hematite equilibrium, suggesting that the formation of the nontronite depends on kinetics. The formation of nanoparticular Na-nontronite at the earlier stage of the experiments appears likely due to their specific thermodynamic properties linked to the nanoscale particle size (i.e., high surface energy and high hydration properties). However, Na-nontronites dissolve when they reach a critical size, leading to the formation of the stable assemblage aegirine and hematite.
Published: 2019
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19. Astronomie et Astrophysique

Author: Rachael M. Roettenbacher, Fabien Baron, Norman Vargas, John B. Lester, Judit Sturmann, Arturo O. Martinez, Olli Majoinen, Chris Farrington, Ettore Pedretti, Nicholas J. Scott, Hilding R. Neilson, Claudia Paladini, T. ten Brummelaar, Miguel Montargès, Gail H. Schaefer, Stephen T. Ridgway, Nathalie D. Thureau, Douglas R. Gies, Xiao Che, Ryan P. Norris, Andrea Chiavassa, Matthew D. Anderson, John D. Monnier, Michael S. Connelley, Laszlo Sturmann, László L. Kiss, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Chiavassa, Andrea
Subjects: Physics, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Star (game theory), Infrared telescope, Center (category theory), FOS: Physical sciences, Astronomy and Astrophysics, Radius, Astrophysics, 01 natural sciences, Spectral line, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, [SDU.ASTR.SR] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Red supergiant, Angular resolution, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Line (formation)
Abstract: We present H-band interferometric observations of the red supergiant (RSG) AZ Cyg made with the Michigan Infra-Red Combiner (MIRC) at the six-telescope Center for High Angular Resolution Astronomy (CHARA) Array. The observations span 5 years (2011-2016), offering insight into the short and long-term evolution of surface features on RSGs. Using a spectrum of AZ Cyg obtained with SpeX on the NASA InfraRed Telescope Facility (IRTF) and synthetic spectra calculated from spherical MARCS, spherical PHOENIX, and SAtlas model atmospheres, we derive $T_{\text{eff}}$ is between $3972 K$ and $4000 K$ and $\log~g$ between $-0.50$ and $0.00$, depending on the stellar model used. Using fits to the squared visibility and Gaia parallaxes we measure its average radius $R=911^{+57}_{-50}~R_{\odot}$. Reconstructions of the stellar surface using our model-independent imaging codes SQUEEZE and OITOOLS.jl show a complex surface with small bright features that appear to vary on a timescale of less than one year and larger features that persist for more than one year. 1D power spectra of these images suggest a characteristic size of $0.52-0.69~R_{\star}$ for the larger, long lived features. This is close to the values of $0.51-0.53~R_{\star}$ derived from 3D RHD models of stellar surfaces. We conclude that interferometric imaging of this star is in line with predictions of 3D RHD models but that short-term imaging is needed to more stringently test predictions of convection in RSGs., 31 pages, 8 tables, 14 figures, accepted to ApJ
Published: 2021

20. Estimating kaolinite crystallinity using near-infrared spectroscopy: implications for its geology on Earth and Mars

Author: Maxime Pineau, Maximilien Mathian, Fabien Baron, Benjamin Rondeau, Laetitia Le Deit, Thierry Allard, Nicolas Mangold, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géosciences [UMR_C 6112] (LPG), Université d'Angers (UA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Nantes université - UFR des Sciences et des Techniques (Nantes univ - UFR ST), Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ), and ANR-16-CE31-0012,MARS-PRIME,Environnement Primitif de Mars(2016)
Subjects: geology, 010506 paleontology, Mars, X-ray difraction, Earth, Earth Analogs for Martian Geological Materials and Processes, 010502 geochemistry & geophysics, near-infrared, 01 natural sciences, Geophysics, Geochemistry and Petrology, Kaolinite, infrared spectroscopy, crystallinity, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
Abstract: Kaolinite is an Al-rich phyllosilicate commonly observed on Earth as a product of the chemical weathering of aluminosilicates. It has also been detected on the martian surface by orbital remote sensing observations. While the determination of the geological processes of formation of terrestrial kaolinite (i.e., hydrothermal activity, continental surface weathering, diagenesis) involves the coupling of field observation and multiple laboratory measurements, only geomorphology and associated minerals are generally available to determine their geological origin on Mars. Kaolinite crystallinity depends on many physicochemical parameters reflecting its conditions of crystallization. To determine if the near-infrared (NIR) spectral signature of kaolinite enables estimation of its crystallinity and furthermore if this method can be used to identify the geological processes involved in kaolinite formation, we carried out an in-depth analysis of NIR spectra of reference terrestrial kaolinites that formed in various geological contexts. We calculated second and third derivatives for each spectrum to highlight subtle variations in the spectral properties of kaolinite. This allowed the identification of 27 spectral contributions for the 4500 and 7000 cm−1 Al-OH-related regions of absorption bands. The position shifts and shape variations of these spectral contributions were intimately linked to variations of crystallinity, which was qualitatively estimated using Hinckley and Liétard XRD (dis)order indices. The results obtained show that the NIR signature of kaolinite is influenced by the stacking disorder of layers that has some influence on the vibrations of the interfoliar and inner Al-OH groups. Our study also confirms that: (1) well-ordered kaolinites are not restricted to hydrothermal deposits; (2) kaolinites from a similar sedimentary or pedogenetic context often display contrasting degrees of crystalline order; and (3) poorly ordered kaolinites are more likely to have a sedimentary or pedogenetic origin. Finally, this work highlights that obtaining spectra with sufficient spectral resolution could help to estimate the crystallinity of kaolinite and, in the best cases, its geological origin, both on Earth and Mars, especially with in situ NIR measurements.
Published: 2021
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21. A multiparametric study on the dissolution of synthetic brannerite

Author: Stéphanie Szenknect, Nicolas Dacheux, Hantao Lin, Fabien Baron, Adel Mesbah, Aurélien Eglinger, Philippe Goncalves, Virginie Chapon, Julien Mercadier, Marion Turuani, Maurice Pagel, Flavien Choulet, Daniel Beaufort, Yann Batonneau, Anne-Magali Seydoux-Guillaume, Institut de Chimie Séparative de Marcoule (ICSM - UMR 5257), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Interfaces de Matériaux en Evolution (LIME), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), IRCELYON-C'Durable (CDURABLE), Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre de recherches sur la géologie des matières premières minérales et énergétiques (CREGU), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Laboratoire Chrono-environnement - CNRS - UBFC (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Interactions Protéine Métal (IPM), Institut de Biosciences et Biotechnologies d'Aix-Marseille (ex-IBEB) (BIAM), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), GeoRessources, Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)-Centre de recherches sur la géologie des matières premières minérales et énergétiques (CREGU)-Institut national des sciences de l'Univers (INSU - CNRS), Université Jean Monnet [Saint-Étienne] (UJM), Biologie végétale et microbiologie environnementale - UMR7265 (BVME), Université de Paris Saclay, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Chrono-environnement (UMR 6249) (LCE), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)
Subjects: Passivation, Materials Science (miscellaneous), Inorganic chemistry, 0211 other engineering and technologies, Sulfuric acid, 02 engineering and technology, Activation energy, Crystal structure, [CHIM.INOR]Chemical Sciences/Inorganic chemistry, 010403 inorganic & nuclear chemistry, 01 natural sciences, 0104 chemical sciences, Amorphous solid, chemistry.chemical_compound, Reaction rate constant, chemistry, Chemistry (miscellaneous), Materials Chemistry, Ceramics and Composites, TA401-492, [CHIM]Chemical Sciences, Dissolution, Materials of engineering and construction. Mechanics of materials, Wet chemistry, 021102 mining & metallurgy
Abstract: Brannerite, UTi2O6 is reported to occur in various uraniferous deposits worldwide. Natural brannerite specimens are found in the amorphous state and are usually considered to be refractory to dissolution due to the formation of TiO2 passivation layer. In the present work, brannerite was synthesized by wet chemistry route, then characterized prior the development of multiparametric dissolution experiments. The evolution of U and Ti concentrations was followed in 0.1–2 mol/L H2SO4 solutions, for temperatures ranging from 25 to 80 °C, in the presence (or not) of 2.8 g/L of dissolved Fe(III). The dissolution of synthetic brannerite was congruent in the whole experimental domain. The formation of Ti-enriched secondary phase at the surface of the brannerite grains was not evidenced. The dissolution rate constants, activation energies and partial orders of the overall dissolution reaction relative to proton activity were determined in the presence (or absence) of Fe(III). The introduction of Fe(III) in sulfuric acid solutions increased the dissolution rate constant by 5 orders of magnitude and induced significant modifications of the apparent activation energy (from 71 ± 4 to 91 ± 6 kJ/mol) and of the partial order relative to proton activity (from 0.42 ± 0.09 to 0.84 ± 0.08). This study suggested that the uncongruency of the brannerite dissolution and the changes usually observed in the rate-controlling step with temperature could be linked to the loss of the crystal structure in natural samples.
Published: 2021
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22. Assessing the redox reactivity of tetrahedral Fe in clay minerals

Author: Thomas B. Hofstetter, Eric Ferrage, Anke Neumann, Jagannath Biswakarma, Sabine Petit, Fabien Baron, and Carolyn I. Pearce
Subjects: Chemistry, Inorganic chemistry, Reactivity (chemistry), Clay minerals, Redox
Published: 2021
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23. UNDERSTANDING THE FORMATION OF CARBONATES ON MARS: EXPERIMENTAL APPROACH

Author: Fabien Baron, Carolina Gil-Lozano, Nicolas Mangold, Vincent Fernandez, Jonathan Hamon, A. Gaudin, and Jean-Pierre Lorand
Subjects: Mars Exploration Program, Geology, Astrobiology
Published: 2021
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24. The growth process of saponite: A study based on particle size distributions and morphological evolution

Author: Chaoqun Zhang, Hongping He, Xiaorong Qin, Alain Decarreau, Fabien Baron, Qi Tao, Jianxi Zhu, Yunfei Xi, and Sabine Petit
Subjects: Geochemistry and Petrology, Geology
Published: 2022
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25. Highly variable content of fluorapatite-hosted COin the Upper Cretaceous/Paleogene phosphorites (Morocco) and implications for paleodepositional conditions

Author: Jérémie Aubineau, Fleurice Parat, Abdellatif Elghali, Otmane Raji, Aissam Addou, Clément Bonnet, Manuel Muñoz, Olivia Mauguin, Fabien Baron, Moulay Brahim Jouti, Oussama Khadiri Yazami, and Jean-Louis Bodinier
Subjects: Geochemistry and Petrology, Geology
Published: 2022
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26. The evolution of saponite: An experimental study based on crystal chemistry and crystal growth

Author: Shangying Li, Brian Grégoire, Sabine Petit, Chaoqun Zhang, Yiping Yang, Qi Tao, Jianxi Zhu, Fabien Baron, Shichao Ji, Hongping He, Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), and Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Materials science, 010504 meteorology & atmospheric sciences, Crystal chemistry, Crystal growth, [CHIM.MATE]Chemical Sciences/Material chemistry, engineering.material, [CHIM.INOR]Chemical Sciences/Inorganic chemistry, 010502 geochemistry & geophysics, 01 natural sciences, Crystallography, Geophysics, Geochemistry and Petrology, engineering, Saponite, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
Abstract: Element incorporation and partitioning during the evolution of clay minerals have significant implications for element cycling in geochemical processes. The main aim of this experimental study is to further our understanding of element redistribution and crystal growth during smectite evolution under different physicochemical conditions. The precursors (i.e., pure Mg- and Ni-saponite) were separately prepared by hydrothermal syntheses at the same set of temperatures (i.e., RT, 50, 150, 180, 200, and 220 °C) for one day. Then the starting materials were obtained from the mechanical mixtures of the identical molar weight of Mg- and Ni-smectite precursors prepared at the same temperature. Subsequently, Series I samples were obtained by hydrothermally treating different starting materials at 220 °C for two weeks while Series II samples were hydrothermally synthesized under various temperatures (220, 300, 400, and 500 °C) for one week using the starting materials prepared at 220 °C. Both the precursors and resultant saponites were characterized by XRD, FTIR, TEM, and STEM. The FTIR spectra of the precursors only exhibit the vMg3OH and vNi3OH bands, corresponding to Mg-saponite and Ni-saponite, respectively. However, the occurrence of vMg2NiOH and vNi2MgOH bands in the resultant saponite indicates the dissolution of the corresponding Mg- and Ni-saponite precursors and recrystallization of Mg-Ni mixed saponite. The dissolution extents of Mg- and Ni-saponite precursors, which affect the degrees of random distribution of octahedral Ni and Mg in resultant Mg, Nisaponite, are significantly controlled by the temperature gap (ΔT) between the precursors prepared and the resultant Mg, Ni-saponite obtained. In general, a larger ΔT leads to a higher dissolution extent of saponite precursors and a higher degree of random distribution of octahedral Ni and Mg cations in the resultant Mg, Ni-saponite structures. Thus, the distribution mode of octahedral cations in saponite, which is not only relevant to a given hydrothermal temperature but also dependent on ΔT for final products, cannot be used as a geothermometer. TEM and STEM observations provide visual evidence that the particles of saponite coarsen when ΔT is higher than zero. Both the crystal-chemical and morphological features during saponite evolution suggest that saponite particles coarsen mainly via partial/complete dissolution of precursors followed by recrystallization and growth of Mg, Ni-saponite in which crystal growth by layer attachment cannot be excluded. This study presents an experimental approach to evaluate the evolution of clay minerals in terms of crystal chemistry and crystal growth and offers a better understanding of the contributions of clay mineral evolution to element cycling.
Published: 2020
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27. VLTI-PIONIER imaging of the red supergiant V602 Carinae

Author: J. C. Guirado, B. Freytag, Andrea Chiavassa, Xavier Haubois, Susanne Höfner, Fabien Baron, Julien Woillez, J. B. Climent, Markus Wittkowski, J. M. Marcaide, European Southern Observatory (ESO), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Uppsala], Uppsala University, Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: Physics, Very Large Telescope, 010308 nuclear & particles physics, Flux, FOS: Physical sciences, Astronomy and Astrophysics, Context (language use), Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 01 natural sciences, law.invention, Telescope, Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, law, Angular diameter, 0103 physical sciences, Red supergiant, 010303 astronomy & astrophysics, Image resolution, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: Context. Red supergiant stars possess surface features and extended molecular atmospheres. Photospheric convection may be a crucial factor of the levitation of the outer atmospheric layers. However, the mechanism responsible is still poorly understood. Aims. We image the stellar surface of V602 Carinae (V602 Car) to constrain the morphology and contrast of the surface features and of the extended atmospheric layers. Methods. We observed V602 Car with the Very Large Telescope Interferometer (VLTI) PIONIER instrument (1.53-1.78 $\mathrm{\mu}$m) between May and July 2016, and April and July 2019 with different telescope configurations. We compared the image reconstructions with 81 temporal snapshots of 3D radiative-hydrodynamics (RHD) CO$^5$BOLD simulations in terms of contrast and morphology, using the Structural Similarity Index. Results. The interferometric data are compatible with an overall spherical disk of angular diameter 4.4$\pm$0.2 mas, and an extended molecular layer. In 2016, the reconstructed image reveals a bright arc-like feature toward the northern rim of the photospheric surface. In 2019, an arc-like feature is seen at a different orientation and a new peak of emission is detected on the opposite side. The contrasts of the reconstructed surface images are 11%$\pm$2% and 9%$\pm$2% for 2016 and 2019, respectively. The morphology and contrast of the two images are consistent with 3D RHD simulations, within our achieved spatial resolution and dynamic range. The extended molecular layer contributes 10--13% of the total flux with an angular diameter of 6--8 mas. It is present but not clearly visible in the reconstructed images because it is close to the limits of the achieved dynamic range. The presence of the molecular layer is not reproduced by the 3D RHD simulations. Conclusions..., Comment: 16 pages, 13 figures, accepted for publication in Astronomy and Astrophysics
Published: 2020

28. The Inner Disk of RY Tau: Evidence of Stellar Occultation by the Disk Atmosphere at the Sublimation Rim from K -band Continuum Interferometry

Author: T. ten Brummelaar, Fabien Baron, Judit Sturmann, Ettore Pedretti, Rafael Millan-Gabet, Claire L. Davies, Robert Parks, Stefan Kraus, Y. Touhami, Rebeca Garcia Lopez, Brian Kloppenborg, Tim J. Harries, Karine Perraut, Laszlo Sturmann, Alicia Aarnio, and John D. Monnier
Subjects: 010504 meteorology & atmospheric sciences, Opacity, FOS: Physical sciences, Astrophysics, 01 natural sciences, CHARA array, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Earth and Planetary Astrophysics (astro-ph.EP), Physics, Photosphere, Line-of-sight, Astronomy and Astrophysics, Position angle, Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Spectral energy distribution, Sublimation (phase transition), Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: We present models of the inner region of the circumstellar disk of RY Tau which aim to explain our near-infrared ($K$-band: $2.1\,\mu$m) interferometric observations while remaining consistent with the optical to near-infrared portions of the spectral energy distribution. Our sub-milliarcsecond resolution CHARA Array observations are supplemented with shorter baseline, archival data from PTI, KI and VLTI/GRAVITY and modeled using an axisymmetric Monte Carlo radiative transfer code. The $K$-band visibilities are well-fit by models incorporating a central star illuminating a disk with an inner edge shaped by dust sublimation at $0.210\pm0.005\,$au, assuming a viewing geometry adopted from millimeter interferometry ($65^{\circ}$ inclined with a disk major axis position angle of $23^{\circ}$). This sublimation radius is consistent with that expected of Silicate grains with a maximum size of $0.36-0.40\,\mu$m contributing to the opacity and is an order of magnitude further from the star than the theoretical magnetospheric truncation radius. The visibilities on the longest baselines probed by CHARA indicate that we lack a clear line-of-sight to the stellar photosphere. Instead, our analysis shows that the central star is occulted by the disk surface layers close to the sublimation rim. While we do not see direct evidence of temporal variability in our multi-epoch CHARA observations, we suggest the aperiodic photometric variability of RY~Tau is likely related temporal and/or azimuthal variations in the structure of the disk surface layers., Comment: Accepted for publication in The Astrophysical Journal
Published: 2020
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29. Geochemical fingerprints of brannerite (UTi 2 O 6 ): an integrated study

Author: Marion Turuani, Yann Batonneau, Daniel Beaufort, Philippe Goncalves, Fabien Baron, Maurice Pagel, Adel Mesbah, Stéphanie Reynaud, Anne-Magali Seydoux-Guillaume, Nicolas Dacheux, Virginie Chapon, Julien Mercadier, Julie Machault, Stephanie Szenknect, Sophie Gouy, Flavien Choulet, Aurélien Eglinger, Laboratoire Chrono-environnement - UFC (UMR 6249) (LCE), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), GeoRessources, Institut national des sciences de l'Univers (INSU - CNRS)-Centre de recherches sur la géologie des matières premières minérales et énergétiques (CREGU)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Institut National de l'Environnement Industriel et des Risques (INERIS), Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Hubert Curien [Saint Etienne] (LHC), Institut d'Optique Graduate School (IOGS)-Université Jean Monnet [Saint-Étienne] (UJM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique UMR6112 (LPG), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA), Hydrogéologie, Argiles, Sols, Altérations (E2) (HydrASA), Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers-Centre National de la Recherche Scientifique (CNRS)-Université de Poitiers-Centre National de la Recherche Scientifique (CNRS), Institut de Biosciences et Biotechnologies d'Aix-Marseille (ex-IBEB) (BIAM), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Interfaces de Matériaux en Evolution (LIME), Institut de Chimie Séparative de Marcoule (ICSM - UMR 5257), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Interactions Protéine Métal (IPM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire Chrono-environnement (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Centre de recherches sur la géologie des matières premières minérales et énergétiques (CREGU), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Hubert Curien (LHC), Institut d'Optique Graduate School (IOGS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Biologie végétale et microbiologie environnementale - UMR7265 (BVME), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Chrono-environnement - CNRS - UFC (UMR 6249) (LCE), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Jean Monnet [Saint-Étienne] (UJM)-Centre National de la Recherche Scientifique (CNRS)-Institut d'Optique Graduate School (IOGS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo France-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo France, Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Chrono-environnement - CNRS - UBFC (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)-Centre de recherches sur la géologie des matières premières minérales et énergétiques (CREGU)-Institut national des sciences de l'Univers (INSU - CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne (UCA)-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Poitiers-Centre National de la Recherche Scientifique (CNRS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Université de Montpellier (UM)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Université de Montpellier (UM)
Subjects: hydrothermal, 0211 other engineering and technologies, Geochemistry, chemistry.chemical_element, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, pegmatite, 02 engineering and technology, Mineral chemistry, 010502 geochemistry & geophysics, 01 natural sciences, Hydrothermal circulation, Geochemistry and Petrology, [CHIM]Chemical Sciences, ComputingMilieux_MISCELLANEOUS, Pegmatite, 021102 mining & metallurgy, 0105 earth and related environmental sciences, fingerprints, Uranium, brannerite, mineral chemistry, chemistry, [SDU]Sciences of the Universe [physics], Leaching (metallurgy), Geology, [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
Abstract: Brannerite (UTi2O6) is among the major uranium-bearing minerals found in ore deposits, however as it has been long considered as a refractory mineral for leaching it is currently disregarded in ore deposits. Brannerite is found in a variety of geological environments with the most common occurrences being hydrothermal and pegmatitic. On the basis of scanning electron microscopy observations coupled with electron probe micro-analyses and laser ablation inductively-coupled plasma mass spectrometer analyses, this study describes the morphological features and the major- and trace-element abundances of brannerite samples from five hydrothermal and five pegmatitic localities across the world. Mineral compositions are also compared with observations from transmission electron microscopy and Raman spectrometry showing that brannerite is amorphous. Significant results include the definition of substitution trends and REE patterns, which are characteristics of either an occurrence or genetic type (hydrothermal and pegmatitic). Hence, in combination, it is possible to obtain reliable constraints for establishing a geochemical classification of brannerite. Inferred fingerprints have direct implications for forensic science and the exploration industry; they also contribute to a better understanding of metallogenic processes and to optimising the extraction of uranium.
Published: 2020
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30. Why chromatic imaging matters

Author: Nuno Gomes, Thomas Henning, Roy van Boekel, Éric Thiébaut, J. Sanchez-Bermudez, J. W. Isbell, Laurent Bourgès, John S. Young, Bruno Lopez, Karl-Heinz Hofmann, Dieter Schertl, Fabien Baron, Paulo J. V. Garcia, Florentin Millour, Gilles Duvert, Alexis Matter, Gerd Weigelt, J.-U. Pott, Isbell, JW [0000-0002-1272-6322], Apollo - University of Cambridge Repository, Observatoire de la Côte d'Azur (OCA), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Computer science, FOS: Physical sciences, Iterative reconstruction, 01 natural sciences, 010309 optics, High angular resolution, Interferometric imaging, 0103 physical sciences, Computer vision, Chromatic scale, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Scientific instrument, Very Large Telescope, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, First generation, Interferometry, [SDU]Sciences of the Universe [physics], Optical interferometry, Space and Planetary Science, Image reconstruction, Artificial intelligence, Astrophysics - Instrumentation and Methods for Astrophysics, business
Abstract: During the last two decades, the first generation of beam combiners at the Very Large Telescope Interferometer has proved the importance of optical interferometry for high-angular resolution astrophysical studies in the near- and mid-infrared. With the advent of 4-beam combiners at the VLTI, the u-v coverage per pointing increases significantly, providing an opportunity to use reconstructed images as powerful scientific tools. Therefore, interferometric imaging is already a key feature of the new generation of VLTI instruments, as well as for other interferometric facilities like CHARA and JWST. It is thus imperative to account for the current image reconstruction capabilities and their expected evolutions in the coming years. Here, we present a general overview of the current situation of optical interferometric image reconstruction with a focus on new wavelength-dependent information, highlighting its main advantages and limitations. As an Appendix we include several cookbooks describing the usage and installation of several state-of-the art image reconstruction packages. To illustrate the current capabilities of the software available to the community, we recovered chromatic images, from simulated MATISSE data, using the MCMC software SQUEEZE. With these images, we aim at showing the importance of selecting good regularization functions and their impact on the reconstruction., Accepted for publication in Experimental Astronomy as part of the topical collection: Future of Optical-infrared Interferometry in Europe
Published: 2018
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31. Establishing α Oph as a Prototype Rotator: Precision Orbit with New Keck, CHARA, and RV Observations

Author: Michael J. Ireland, Judit Sturmann, T. ten Brummelaar, Stefan Kraus, Francis C. Fekel, Adam L. Kraus, John D. Monnier, Rachael M. Roettenbacher, Laszlo Sturmann, Michael H. Williamson, Fabien Baron, Sasha Hinkley, Tyler Gardner, and Gail Schaefer
Subjects: Chara, Physics, biology, Astronomy, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, biology.organism_classification, 01 natural sciences, 010309 optics, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Orbit (control theory), 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: Alpha Ophiuchi (Rasalhague) is a nearby rapidly rotating A5IV star which has been imaged by infrared interferometry. $\alpha$ Oph is also part of a known binary system, with a companion semi-major axis of $\sim$430 milli-arcseconds and high eccentricity of 0.92. The binary companion provides the unique opportunity to measure the dynamical mass to compare with the results of rapid rotator evolution models. The lack of data near periastron passage limited the precision of mass measurements in previous work. We add new interferometric data from the MIRC combiner at the CHARA Array as well as new Keck adaptive optics imaging data with NIRC2, including epochs taken near periastron passage. We also obtained new radial velocities of both components at Fairborn Observatory. Our updated combined orbit for the system drastically reduces the errors of the orbital elements, and allows for precise measurement of the primary star mass at the few percent level. Our resulting primary star mass of $2.20\pm0.06$ M$_{\odot}$ agrees well with predictions from imaging results, and matches evolution models with rotation when plotting on an HR diagram. However, to truly distinguish between non-rotating and rotating evolution models for this system we need $\sim$1\% errors on mass, which might be achieved once the distance is known to higher precision in future Gaia releases. We find that the secondary mass of $0.824\pm0.023$ M$_{\odot}$ is slightly under-luminous when compared to stellar evolution models. We show that $\alpha$ Oph is a useful reference source for programs that need $\pm$1 milli-arcsecond astrometry., Comment: 17 pages, 7 figures, accepted for publication in ApJ
Published: 2021
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32. New Constraints on Early Mars Weathering Conditions From an Experimental Approach on Crust Simulants

Author: Jean-Pierre Lorand, N. Mangold, Fabien Baron, A. Gaudin, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), and Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Martian, Mineral, 010504 meteorology & atmospheric sciences, Geochemistry, Crust, Weathering, Mars Exploration Program, 15. Life on land, 01 natural sciences, chemistry.chemical_compound, Geophysics, [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology, chemistry, 13. Climate action, Space and Planetary Science, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Environmental science, Carbonate, Chemical composition, Earth (classical element), 0105 earth and related environmental sciences
Abstract: International audience; A denser CO 2 atmosphere and higher temperatures than present-day conditions are frequently invoked as prevailing conditions for the formation of some ancient hydrous mineralogical associations present at the surface of Mars. The environmental conditions are of particular interest to better understand and constrain the weathering processes of the early Martian crust. For this purpose, 6-month-long batch weathering experiments on Martian crust simulants and individual Martian mineral analogs were performed at low temperature (45°C) under a dense CO 2 atmosphere (1 atm). Constraints on the weathering conditions are deduced from the solution properties and thermodynamic calculations, as well as mass balance calculations. Experimental solutions vary from mildly acidic to near neutral (4.75-6.48 pH). The Eh-pH conditions (Eh from 0.189-0.416 V/standard hydrogen electrode) suggest favorable conditions for the formation of ferric minerals despite an anoxic CO 2 atmosphere. The chemical weathering appears to be 4 times more intense for Martian simulants under a CO 2 atmosphere than under Earth ambient air. The weathering trend under a CO 2 atmosphere involves leaching of alkali and alkaline earth elements (Mg, Ca, Na, and K) and Si and enrichments of the solid phases in Al, Fe, and to a lesser extent Si compared to the initial chemical composition of the starting minerals. This geochemical partitioning between solution and solids resembles those deduced from weathering profiles on Earth. Our results strongly support the idea that carbonates could not have extensively formed at the surface of early Mars despite a dense CO 2 atmosphere. Plain Language Summary Mars orbital and landed missions have provided mineralogical, morphological, and field evidence for liquid water at the surface approximately 3.5 billion years ago. The chemical and mineralogical composition of the Martian rocks have potentially been modified by interaction with this liquid water. The purpose of our study is to use laboratory experiments to constrain the physicochemical conditions of water resulting from the chemical weathering of Martian crust simulants under an atmosphere composed of carbon dioxide, as is the case for Mars. The water in contact with simulants is mildly acidic. The partitioning of chemical elements between the solution and minerals is similar to what is observed on Earth, but weathering is more intense. Despite that Mars had a primitive CO 2-dense atmosphere, the conditions were not favorable to the extensive formation of carbonate at the surface.
Published: 2019
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33. Constraining convection across the AGB with high-angular-resolution observations

Author: J. Kluska, Alain Jorissen, S. Shetye, Christos Siopis, Markus Wittkowski, B. Freytag, J.-B. Le Bouquin, Sofia Ramstedt, Jean-Phillipe Berger, J. Hron, Andrea Chiavassa, S. Van Eck, A. Mayer, G. Sadowski, Claudia Paladini, Fabien Baron, K. Kravchenko, and Franz Kerschbaum
Subjects: Convection, mass loss [stars], Granule (solar physics), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 0103 physical sciences, Asymptotic giant branch, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Astrophysique, convection, Physics, Photosphere, Very Large Telescope, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, high angular resolution [techniques], Astronomy and Astrophysics, Effective temperature, Astronomie, Surface gravity, AGB and post-AGB [stars], imaging [stars], interferometric [techniques], Interferometry, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics
Abstract: We present very detailed images of the photosphere of an AGB star obtained with the PIONIER instrument, installed at the Very Large Telescope Interferometer (VLTI). The images show a well defined stellar disc populated by a few convective patterns. Thanks to the high precision of the observations we are able to derive the contrast and granulation horizontal scale of the convective pattern for the first time in a direct way. Such quantities are then compared with scaling relations between granule size, effective temperature, and surface gravity that are predicted by simulations of stellar surface convection., SCOPUS: ar.k, info:eu-repo/semantics/published
Published: 2019

34. Quantification of coffinite (USiO4) in roll-front uranium deposits using visible to near infrared (Vis-NIR) portable field spectroscopy

Author: Adel Mesbah, Karl Lelievre, Adrien Pouradier, Régis Roy, Daniel Beaufort, Nicolas Dacheux, Benoit Hebert, Valentin Robin, Fabien Baron, Ruslan Jikibayev, Stéphanie Szenknect, Hydrogéologie, Argiles, Sols, Altérations (E2) (HydrASA), Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Cavendish Laboratory, University of Cambridge [UK] (CAM), Groupement de Recherche Eau, Sol, Environnement (GRESE), Université de Limoges (UNILIM), Interfaces de Matériaux en Evolution (LIME), Institut de Chimie Séparative de Marcoule (ICSM - UMR 5257), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Mineral, Materials science, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Near-infrared spectroscopy, chemistry.chemical_element, Mineralogy, 010501 environmental sciences, Uranium, 010502 geochemistry & geophysics, Mass spectrometry, 01 natural sciences, Uranium ore, chemistry, Geochemistry and Petrology, Absorption band, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Economic Geology, Coffinite, Absorption (electromagnetic radiation), ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
Abstract: Coffinite (USiO4) is a common uranium-bearing mineral of roll-front uranium deposits. This mineral can be identified by the visible near infrared (Vis-NIR) portable field spectrometers used in mining exploration. However, due to the low detection limits and associated errors, the quantification of coffinite abundance in the mineralized sandstones or sandy sediments of roll-front uranium deposits using Vis-NIR spectrometry requires a specific methodological development. In this study, the 1135 nm absorption band area is used to quantify the abundance of coffinite. This absorption feature does not interfere with NIR absorption bands of any other minerals present in natural sands or sandstones of uranium roll-front deposits. The correlation between the 1135 nm band area and coffinite content was determined from a series of spectra measured from prepared mineral mixtures. The samples were prepared with a range of weighted amounts of arenitic sands and synthetic coffinite simulating the range of uranium concentration encountered in roll-front uranium deposits. The methodology presented in this study provides the quantification of the coffinite content present in sands between 0.03 wt% to 1 wt% coffinite with a detection limit as low as 0.005 wt%. The integrated area of the 1135 nm band is positively correlated with the coffinite content of the sand in this range, showing that the method is efficient to quantify coffinite concentrations typical of roll-front uranium deposits. The regression equation defined in this study was then used as a reference to predict the amount of natural coffinite in a set of mineralized samples from the Tortkuduk uranium roll-front deposit (South Kazakhstan).
Published: 2019
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35. Direct synthesis of pure brannerite UTi2O6

Author: Fabien Baron, Daniel Beaufort, Adel Mesbah, Flavien Choulet, Maurice Pagel, Philippe Goncalves, Anne-Magali Seydoux-Guillaume, Aurélien Eglinger, Yann Batonneau, Julien Mercadier, Nicolas Clavier, Stéphanie Szenknect, Hantao Lin, Virginie Chapon, Marion Turuani, Nicolas Dacheux, Interfaces de Matériaux en Evolution (LIME), Institut de Chimie Séparative de Marcoule (ICSM - UMR 5257), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre de recherches sur la géologie des matières premières minérales et énergétiques (CREGU), Laboratoire Chrono-environnement (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Institut de Biosciences et Biotechnologies d'Aix-Marseille (ex-IBEB) (BIAM), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Interactions Protéine Métal (IPM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire Chrono-environnement - CNRS - UBFC (UMR 6249) (LCE), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université d'Angers (UA)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Poitiers-Centre National de la Recherche Scientifique (CNRS), Laboratoire Chrono-environnement - CNRS - UFC (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne (UCA)-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Nuclear and High Energy Physics, Uranium titanate, Materials science, uranium hydroxide Corresponding author, Uranium dioxide, [SDU.STU.PE]Sciences of the Universe [physics]/Earth Sciences/Petrography, chemistry.chemical_element, 02 engineering and technology, 01 natural sciences, Uranium hydroxide, 010305 fluids & plasmas, chemistry.chemical_compound, Impurity, 0103 physical sciences, Brannerite, [CHIM]Chemical Sciences, General Materials Science, Oxide minerals, Precipitation (chemistry), Uranium, 021001 nanoscience & nanotechnology, Nuclear Energy and Engineering, chemistry, X-ray crystallography, Hydroxide, 0210 nano-technology, Titanium, Nuclear chemistry
Abstract: International audience; A new method based on the precipitation of uranium(IV) and titanium(IV) hydroxide precursors was developed to prepare pure brannerite UTi2O6 samples. In fact, U(IV) dissolved in HCl (6 mol L−1) was mixed to Ti (IV) alkoxyde before a basification step with an excess of NH4OH to obtain a highly reactive nanometric (U,Ti)(OH)4 powder. The obtained powder was then dried under vacuum, pressed into pellets and finally fired at 1300 °C. This method led to the formation of pure brannerite in contrast to previous reported protocols, which showed the formation of impurities such us UO2 and TiO2. The refined unit cell parameters of UTi2O6 led to a = 9.8113(2) Å, b = 3.7681(1) Å, c = 6.9232(1) Å, β = 118.94(1)° and V = 223.9(1) Å3.
Published: 2019
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36. Quantitative Raman calibration of sulfate-bearing polymineralic mixtures: a S quantification in sedimentary rocks on Mars

Author: Catherine Guillot-Deudon, Chloé Larre, Fabien Baron, Nicolas Mangold, Yann Morizet, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université d'Angers (UA)-Université de Nantes - Faculté des Sciences et des Techniques, Institut des Matériaux Jean Rouxel (IMN), Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA), Cavendish Laboratory, and University of Cambridge [UK] (CAM)
Subjects: 010504 meteorology & atmospheric sciences, Mineralogy, Mars, Martian soil, engineering.material, S abundance, 010502 geochemistry & geophysics, 01 natural sciences, chemistry.chemical_compound, symbols.namesake, [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology, Geochemistry and Petrology, Silicate minerals, Plagioclase, Sulfate, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Basalt, sulfates, Olivine, Mars Exploration Program, sedimentary 38 rocks, chemistry, 13. Climate action, [SDU]Sciences of the Universe [physics], Raman spectroscopy, engineering, symbols, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Geology, [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
Abstract: The NASA 2020 Mars mission is a Curiosity-type rover whose objective is to improve the knowledge of the geological and climatic evolution of Mars and to collect rock samples for return to Earth. The new rover has a payload of seven instruments including the SuperCam instrument which consists of four tools including a Raman spectrometer. This Raman device will be non-destructive and will analyse the surface remotely in order to determine the mineralogy of rocks and, by extent, to detect and quantify major elements such as sulfur. Sulfur has been detected as sulfate (Ca,Mg,Fe-sulfates) in sedimentary rocks. This element is difficult to quantify using the laser ablation tool of the ChemCam instrument on-board the Curiosity rover.We propose a Raman calibration to constrain the sulfur abundance in polymineralic mixtures. We acquired Raman signatures on binary and ternary mechanical mixtures containing Ca and Mg sulfates, mixed with natural silicate minerals supposed to be relevant to basaltic-sedimentary rocks at the surface of Mars: olivine, clinopyroxene, orthopyroxene and plagioclase. Using the Voigt function to process the Raman spectra from samples extracted from our mixtures allows us to calculate the initial proportions of our preparations of Ca and Mg sulfates. From these simulations, calibration equations have been provided allowing us to determine sulfate proportions (CaSO4and MgSO4) in a mixture with basaltic minerals. With the presented calibration, S can be quantified at a lower limit of 0.7 wt.% in Martian soil.
Published: 2019
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37. Multiplicity of Galactic Cepheids from long-baseline interferometry. IV. New detected companions from MIRC and PIONIER observations

Author: Nancy R. Evans, Fabien Baron, Alexandre Gallenne, Wolfgang Gieren, S. Borgniet, Paulina Karczmarek, Grzegorz Pietrzyński, Pierre Kervella, Antoine Mérand, Gail H. Schaefer, John Monnier, Richard I. Anderson, and Rachael M. Roettenbacher
Subjects: Physics, 010308 nuclear & particles physics, Cepheid variable, FOS: Physical sciences, Binary number, Astronomy and Astrophysics, Astrophysics, Astrometry, 01 natural sciences, Interferometry, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Multiplicity (chemistry), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: We aim at detecting and characterizing the main-sequence companions of a sample of known and suspected Galactic binary Cepheids. We used the multi-telescope interferometric combiners MIRC and PIONIER to detect and measure the astrometric positions of the high-contrast companions orbiting 16 bright Galactic Cepheids. We made use of the CANDID algorithm to search for the companions and set detection limits. We also present new high-precision RVs which were used to fit radial pulsation and orbital velocities. We report the detection of the companions orbiting the Cepheids U Aql, BP Cir, and S Mus, possible detections for FF Aql, Y Car, BG Cru, X Sgr, V350 Sgr, and V636 Sco, while no component is detected around U Car, YZ Car, T Mon, R Mus, S Nor, W Sgr and AH Vel. For U Aql and S Mus, we performed a preliminary orbital fit combining astrometry with new high-precision RVs, providing the full set of orbital and pulsation parameters. Assuming the distance, we estimated preliminary masses of M(U Aql) = 4.97+/-0.62Msun and M(S Mus) = 4.63+/-0.99Msun. For YZ Car, W Sgr, V350 Sgr, and V636 Sco, we revised the spectroscopic orbits using new high-precision RVs, while we updated the pulsation parameters for BP Cir, BG Cru, S Nor and AH Vel. Our interferometric observations also provide measurements of the angular diameters, that can be used in a Baade-Wesselink type analysis. We have now several astrometric detections of Cepheid companions. When RVs of the companions will be available, such systems will provide accurate and independent masses and distances. Orbital parallaxes with an accuracy, 29 pages, 11 figures, 23 tables. Accepted for publication in A&A
Published: 2018

38. Probing the Inner Disk Emission of the Herbig Ae Stars HD 163296 and HD 190073

Author: Y. Touhami, Jean-Baptiste Le Bouquin, Michael L. Sitko, Stefan Kraus, Nuria Calvet, Jean-Philippe Berger, Judit Sturmann, Fabien Baron, Alicia Aarnio, Brian Kloppenborg, Claire L. Davies, Michel Curé, T. ten Brummelaar, Rafael Millan-Gabet, Benjamin R. Setterholm, Adam E. Rubinstein, John D. Monnier, Alexander Kreplin, and S. Kanaan
Subjects: Physics, 010308 nuclear & particles physics, Library science, FOS: Physical sciences, Astronomy and Astrophysics, 01 natural sciences, Institutional support, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, 0103 physical sciences, 010303 astronomy & astrophysics, Vice president, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: The physical processes occurring within the inner few astronomical units of proto-planetary disks surrounding Herbig Ae stars are crucial to setting the environment in which the outer planet-forming disk evolves and put critical constraints on the processes of accretion and planet migration. We present the most complete published sample of high angular resolution H- and K-band observations of the stars HD 163296 and HD 190073, including 30 previously unpublished nights of observations of the former and 45 nights of the latter with the CHARA long-baseline interferometer, in addition to archival VLTI data. We confirm previous observations suggesting significant near-infrared emission originates within the putative dust evaporation front of HD 163296 and show this is the case for HD 190073 as well. The H- and K-band sizes are the same within $(3 \pm 3)\%$ for HD 163296 and within $(6 \pm 10)\%$ for HD 190073. The radial surface brightness profiles for both disks are remarkably Gaussian-like with little or no sign of the sharp edge expected for a dust evaporation front. Coupled with spectral energy distribution analysis, our direct measurements of the stellar flux component at H and K bands suggest that HD 190073 is much younger (, 19 pages, 6 figures
Published: 2018

39. A Geometrical 1% Distance to the Short-period Binary Cepheid V1334 Cygni

Author: Dariusz Graczyk, Wolfgang Gieren, S. Borgniet, Bogumił Pilecki, Charles Proffitt, Antoine Mérand, Rachael M. Roettenbacher, John D. Monnier, Richard I. Anderson, Laurent Eyer, Stefan Kraus, Pierre Kervella, E. Nelan, Mónica Taormina, Alexandre Gallenne, E. Winston, Fabien Baron, Grzegorz Pietrzyński, Nancy Remage Evans, Nami Mowlavi, Gail H. Schaefer, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie et des Matériaux Paris-Est (ICMPE), Institut de Chimie du CNRS (INC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), European Southern Observatory (ESO), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Neovia, Geneva Observatory, University of Geneva [Switzerland], Université de Genève = University of Geneva (UNIGE), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Cepheid variable, Library science, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Institutional support, Observatory, Hubble space telescope, 0103 physical sciences, media_common.cataloged_instance, Astrophysics::Solar and Stellar Astrophysics, European union, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, media_common, Physics, [PHYS]Physics [physics], 010308 nuclear & particles physics, European research, Astronomy and Astrophysics, language.human_language, Flemish, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, language, Christian ministry, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Cepheid stars play a considerable role as extragalactic distances indicators, thanks to the simple empirical relation between their pulsation period and their luminosity. They overlap with that of secondary distance indicators, such as Type Ia supernovae, whose distance scale is tied to Cepheid luminosities. However, the Period-Luminosity (P-L) relation still lacks a calibration to better than 5%. Using an original combination of interferometric astrometry with optical and ultraviolet spectroscopy, we measured the geometrical distance d = 720.35+/-7.84 pc of the 3.33 d period Cepheid V1334 Cyg with an unprecedented accuracy of +/-1 %, providing the most accurate distance for a Cepheid. Placing this star in the P-L diagram provides an independent test of existing period-luminosity relations. We show that the secondary star has a significant impact on the integrated magnitude, particularly at visible wavelengths. Binarity in future high precision calibrations of the P-L relations is not negligible, at least in the short-period regime. Subtracting the companion flux leaves V1334 Cyg in marginal agreement with existing photometric-based P-L relations, indicating either an overall calibration bias or a significant intrinsic dispersion at a few percent level. Our work also enabled us to determine the dynamical masses of both components, M1 = 4.288 +/- 0.133 Msun (Cepheid) and M2 = 4.040 +/- 0.048 Msun (companion), providing the most accurate masses for a Galactic binary Cepheid system., Comment: Accepted for publication in ApJ
Published: 2018
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40. The fundamentals: angular diameter measurements of zero-crossing stars from the NPOI

Author: Ellyn K. Baines, Henrique R. Schmitt, James A. Benson, R. T. Zavala, Fabien Baron, and J. Thomas Armstrong
Subjects: Physics, Bright giant, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Navy Precision Optical Interferometer, Stellar classification, Luminosity, Stars, Angular diameter, Limb darkening, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Supergiant, Astrophysics::Galaxy Astrophysics
Abstract: We recently used archival and newly obtained data from the Navy Precision Optical Interferometer to measure the fundamental properties of 87 stars. The sample consisted of 5 dwarfs, 3 subgiants, 69 giants, 3 bright giants, and 7 supergiants, and spanned a wide range of spectral classes from B to M. We combined our angular diameters with photometric and distance information from the literature to determine each star’s physical radius, effective temperature, bolometric flux, luminosity, mass, and age. Several dozen of the stars have visibility curves sampled down to the first null, where the visibilities drop to zero. Here we present preliminary results showing limb-darkening fits for the five zero crossing stars that have the best coverage of the second lobe.
Published: 2018
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41. Planet formation imager: project update

Author: Gerd Weigelt, Ernest A. Michael, Florentin Millour, Andrea Isella, Edward H. Wishnow, Kaitlin M. Kratter, Eric L. N. Jensen, Jean Baptiste Le Bouquin, Stephen T. Ridgway, Jean François Gonzalez, Rafael Millan-Gabet, Farzana Meru, David R. Ciardi, Neal J. Turner, Greg Laughlin, Cristina Ramos Almeida, Almudena Alonso-Herrero, S. F. Hoenig, Ming Zhao, Claudia Paladini, Zhaohuan Zhu, Amy Bonsor, O. Panić, L. H. Quiroga-Nuñez, Stephen R. Kane, Ruobing Dong, Stefano Minardi, Andrea Chiavassa, Stephen A. Rinehart, Amelia Bayo, T. ten Brummelaar, Jean Surdej, Alexander Wallace, Attila Juhasz, John D. Ilee, Benjamin J. S. Pope, Matthias R. Schreiber, Konrad R. W. Tristram, Jean Philippe Berger, Gerard T. van Belle, Willem Jan De Wit, Richard P. Nelson, Johan Olofsson, Joerg Uwe Pott, Michael J. Ireland, John Young, Fabien Baron, Mark Reynolds, Sean N. Raymond, Wilhelm Kley, Alessandro Morbidelli, Sebastian Wolf, Tabetha S. Boyajian, Michelle Creech-Eakman, Peter G. Tuthill, Gaspard Duchene, Chris Packham, S. Zúñiga-Fernández, Rene D. Oudmaijer, Sylvestre Lacour, Quentin Kral, Makoto Kishimoto, Lucas Labadie, G. Vasisht, Catherine Espaillat, Poshak Gandhi, Michael D. Smith, Denis Defrere, Andreas Morlok, Chris Mordasini, D. Mozurkewich, Keivan G. Stassun, John D. Monnier, Alexandre Gallenne, Zsolt Regaly, Stefan Kraus, Christopher A. Haniff, Romain Petrov, Markus Wittkowski, Department of Astronomy [Ann Arbor], University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Cavendish Laboratory, University of Cambridge [UK] (CAM), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), European Southern Observatory (ESO), Universidad de Concepción [Chile], School of Physics and Astronomy [Southampton], University of Southampton, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), University of Cyprus [Nicosia], Michelson Science Center (MSC), California Institute of Technology (CALTECH), Friedrich-Schiller-Universität Jena, Centre de Recherches Pétrographiques et Géochimiques (CRPG), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Queen Mary University of London (QMUL), Institut für Astronomie, Universität Wien (IFA), Universität Wien, ECLIPSE 2018, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), School of Computer Science and Software Engineering [Australia], The University of Western Australia (UWA), National Optical Astronomy Observatory (NOAO), Institut d'Astrophysique et de Géophysique [Liège], Université de Liège, Max-Planck-Institut für Radioastronomie (MPIFR), Department of Materials Science and Engineering, Institute of Ceramics and Glass-Friedrich Alexander University [Erlangen-Nürnberg], Harbin University of Commerce [Heilongjiang], Center for High Angular Resolution Astronomy (CHARA), Georgia State University, University System of Georgia (USG)-University System of Georgia (USG), Space Sciences, Technologies and Astrophysics Research Institute (STAR), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Friedrich-Schiller-Universität = Friedrich Schiller University Jena [Jena, Germany], Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Institute of Ceramics and Glass-Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), University of Michigan System, Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Universidad de Concepción - University of Concepcion [Chile], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Cyprus [Nicosia] (UCY), Friedrich-Alexander Universität Erlangen-Nürnberg (FAU)-Institute of Ceramics and Glass, Creech-Eakman, Michelle J., Tuthill, Peter G., and Mérand, Antoine
Subjects: Computer science, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Technology development, Protoplanetary disk, 01 natural sciences, PFI, 010309 optics, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, CubeSat, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Planet formation, Earth and Planetary Astrophysics (astro-ph.EP), Infrared interferometry, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Large aperture, Exoplanet, Interferometry, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: The Planet Formation Imager (PFI) is a near- and mid-infrared interferometer project with the driving science goal of imaging directly the key stages of planet formation, including the young proto-planets themselves. Here, we will present an update on the work of the Science Working Group (SWG), including new simulations of dust structures during the assembly phase of planet formation and quantitative detection efficiencies for accreting and non-accreting young exoplanets as a function of mass and age. We use these results to motivate two reference PFI designs consisting of a) twelve 3m telescopes with a maximum baseline of 1.2km focused on young exoplanet imaging and b) twelve 8m telescopes optimized for a wider range of young exoplanets and protoplanetary disk imaging out to the 150K H2O ice line. Armed with 4x8m telescopes, the ESO/VLTI can already detect young exoplanets in principle and projects such as MATISSE, Hi-5 and Heimdallr are important PFI pathfinders to make this possible. We also discuss the state of technology development needed to make PFI more affordable, including progress towards new designs for inexpensive, small field-of-view, large aperture telescopes and prospects for Cubesat-based space interferometry., Comment: Presented at 2018 SPIE Astronomical Telescopes + Instrumentation, Austin, Texas, USA. See www.planetformationimager.org for more information
Published: 2018
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42. Identifying the phyllosilicate minerals of hypogene ore deposits in lateritic saprolites using the near-IR spectroscopy second derivative methodology

Author: Fabien Baron, Renan Furic, Sabine Petit, Benoit Hebert, Jean-Luc Lescuyer, Maximilien Mathian, Daniel Beaufort, Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de recherche pour le développement [IRD] : UR206-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de recherche pour le développement [IRD] : UR206-Centre National de la Recherche Scientifique (CNRS)
Subjects: Field-based near-infrared spectroscopy, Hypogene, Mineralogy, 020101 civil engineering, 02 engineering and technology, Laterite, engineering.material, 010502 geochemistry & geophysics, 01 natural sciences, 0201 civil engineering, chemistry.chemical_compound, Geochemistry and Petrology, Prospecting, Kaolinite, [CHIM]Chemical Sciences, Chlorite, 0105 earth and related environmental sciences, Muscovite, Alteration halo, Saprolite, Clay minerals, Mining geology, chemistry, engineering, Economic Geology, Geology
Abstract: International audience; Infrared field-based reflectance spectroscopy in the Visible-Near-Infrared-Shortwave Infrared (VIS-NIR-SWIR) domain is a useful tool in mining geology particularly efficient for investigating the clay mineralogy of alteration haloes around ore deposits. It is used as a routine technique for the basic identification, mapping and semi-quantification of clay mineral species. However, the use of this technique for prospecting in hypogene deposits at depth in intertropical areas is strongly limited because of the presence of a thick, kaolinite-rich lateritic cover. Due to the strong IR absorption of kaolinite and the overlapping of its IR bands with those of most of the phyllosilicates in the SWIR domain, the use of field based near-infrared spectroscopy does not permit efficient identification and mapping of the phyllosilicates inherited from hypogene alteration that persist in the saprolite of lateritic profiles. In this paper, we propose a methodology to enhance the detection and semi-quantification of hypogene phyllosilicate minerals in kaolinite-rich lateritic saprolites using calibration curves. Those curves are built from the NIR spectra of binary admixtures of kaolinite or smectite with muscovite, Fe-Mg chlorite, clinochlore or talc in different known proportions. For each admixture series, calibration curves were established, based on investigation of two regions of interest within the NIR domain (1350–1470 nm and 2080–2500 nm) using a field-based spectrometer. For each binary mixture series of phyllosilicates, the second derivative of the NIR spectra was used to enhance the detection of the diagnostic absorption bands of each type of phyllosilicate, and hence to optimize the calculation of the intensity ratios between the diagnostic bands of the phyllosilicate components as a function of their percentage in the mixture. In presence of large amounts of lateritic kaolinite, the detection limit of the major types of hypogene phyllosilicates has been found at ranges from 5 to 10 wt% of the total clay content using the second derivative of the NIR spectra acquired with a field-based spectrometer. Above these aforementioned limits of detection, the semi-quantitative data obtained by comparing the NIR reflectance spectra of natural samples with those of the calibration curves could permit to map hypogene alteration haloes directly from the lateritic sa-prolite. Finally the described approach has been successfully tested on natural samples from the skarn deposits of the Ity gold mine (Ivory Coast).
Published: 2018
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43. Precision Orbit of δ Delphini and Prospects for Astrometric Detection of Exoplanets

Author: Douglas K. Duncan, Ming Zhao, Daniel Huber, Gail Schaefer, Fabien Baron, Fred C. Adams, Stefan Kraus, Samuel J. Swihart, Travis Barman, Judit Sturmann, T. ten Brummelaar, Xiao Che, Tyler Gardner, John D. Monnier, Francis C. Fekel, Michael H. Williamson, Timothy R. White, Rachael M. Roettenbacher, Laszlo Sturmann, and Michael J. Ireland
Subjects: close [binaries], detection [planets and satellites], F-TYPE, Library science, SURFACE BRIGHTNESS, spectroscopic [binaries], 01 natural sciences, Institutional support, CLASSIFICATION, CHARA array, 010309 optics, Observatory, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, SCUTI STARS, 010303 astronomy & astrophysics, Vice president, Astrophysics::Galaxy Astrophysics, CHARA ARRAY, Physics, RADIAL-VELOCITY, European research, visual [binaries], Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Exoplanet, BINARY-SYSTEMS, Astrophysics - Solar and Stellar Astrophysics, SUBSTELLAR COMPANIONS, 13. Climate action, Space and Planetary Science, A-TYPE STARS, SYNCHRONIZATION, astrometry, Astrophysics::Earth and Planetary Astrophysics
Abstract: Combining visual and spectroscopic orbits of binary stars leads to a determination of the full 3D orbit, individual masses, and distance to the system. We present a full analysis of the evolved binary system $\delta$ Delphini using astrometric data from the MIRC and PAVO instruments on the CHARA long-baseline interferometer, 97 new spectra from the Fairborn Observatory, and 87 unpublished spectra from Lick Observatory. We determine the full set of orbital elements for $\delta$ Del, along with masses of $1.78 \pm 0.07$ $M_{\odot}$ and $1.62 \pm 0.07$ $M_{\odot}$ for each component, and a distance of $63.61 \pm 0.89$ pc. These results are important in two contexts: for testing stellar evolution models and defining the detection capabilities for future planet searches. We find that the evolutionary state of this system is puzzling, as our measured flux ratios, radii, and masses imply a $\sim$ 200 Myr age difference between the components using standard stellar evolution models. Possible explanations for this age discrepancy include mass transfer scenarios with a now ejected tertiary companion. For individual measurements taken over a span of 2 years we achieve $2$ M$_{J}$ on orbits $>0.75$ AU around individual components of hot binary stars via differential astrometry., Comment: 28 pages, 14 figures, accepted for publication in ApJ
Published: 2018
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44. Simultaneous Spectral Energy Distribution and Near-infrared Interferometry Modeling of HD 142666

Author: David M. Acreman, Laszlo Sturmann, T. ten Brummelaar, Fabien Baron, Stefan Kraus, Judit Sturmann, John D. Monnier, Alexander Kreplin, Tim J. Harries, Rafael Millan-Gabet, Aaron Labdon, Claire L. Davies, and Brian Kloppenborg
Subjects: Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 010305 fluids & plasmas, law.invention, law, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, Near-infrared spectroscopy, Astronomy and Astrophysics, Scale height, Position angle, Interferometry, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Closure phase, Spectral energy distribution, Astrophysics::Earth and Planetary Astrophysics, Hydrostatic equilibrium
Abstract: We present comprehensive models of Herbig Ae star, HD 142666, which aim to simultaneously explain its spectral energy distribution (SED) and near-infrared (NIR) interferometry. Our new sub-milliarcsecond resolution CHARA (CLASSIC and CLIMB) interferometric observations, supplemented with archival shorter baseline data from VLTI/PIONIER and the Keck Interferometer, are modeled using centro-symmetric geometric models and an axisymmetric radiative transfer code. CHARA's 330 m baselines enable us to place strong constraints on the viewing geometry, revealing a disk inclined at 58 degrees from face-on with a 160 degree major axis position angle. Disk models imposing vertical hydrostatic equilibrium provide poor fits to the SED. Models accounting for disk scale height inflation, possibly induced by turbulence associated with magneto-rotational instabilities, and invoking grain growth to >1 micron size in the disk rim are required to simultaneously reproduce the SED and measured visibility profile. However, visibility residuals for our best model fits to the SED indicate the presence of unexplained NIR emission, particularly along the apparent disk minor axis, while closure phase residuals indicate a more centro-symmetric emitting region. In addition, our inferred 58 degree disk inclination is inconsistent with a disk-based origin for the UX Ori-type variability exhibited by HD 142666. Additional complexity, unaccounted for in our models, is clearly present in the NIR-emitting region. We propose the disk is likely inclined toward a more edge-on orientation and/or an optically thick outflow component also contributes to the NIR circumstellar flux., Accepted for publication in The Astrophysical Journal
Published: 2018
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45. Heterogeneous photo-Fenton decolorization of Orange II over Al-pillared Fe-smectite: Response surface approach, degradation pathway, and toxicity evaluation

Author: Juanjuan Qiu, Luojing Xiang, Sabine Valange, Sabine Petit, Fabien Baron, Joël Barrault, M. V. Sivaiah, Qianqian Huang, Huiyuan Li, Hui Zhang, Yanli Li, Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), and Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Poitiers-Institut de Chimie du CNRS (INC)
Subjects: inorganic chemicals, Environmental Engineering, Central composite design, Ultraviolet Rays, Iron, Health, Toxicology and Mutagenesis, Kinetics, Al-pillared Fe-smectite, Heterogeneous catalysis, Catalysis, chemistry.chemical_compound, X-Ray Diffraction, Response surface methodology, Toxicity Tests, Aluminum Oxide, medicine, Animals, Environmental Chemistry, Hydrogen peroxide, Waste Management and Disposal, Chromatography, Chemistry, Silicates, Benzenesulfonates, Hydrogen Peroxide, Orange II, Degradation pathway, [CHIM.CATA]Chemical Sciences/Catalysis, Pollution, Heterogeneous photo-Fenton, Daphnia, Aluminium oxide, Ferric, Azo Compounds, Oxidation-Reduction, medicine.drug, Nuclear chemistry
Abstract: International audience; A ferric smectite clay material was synthesized and further intercalated with Al2O3 pillars for the first time with the aim of evaluating its ability to be used as heterogeneous catalyst for the photo-Fenton decolorization of azo dye Orange II. UV irradiation was found to enhance the activity of the catalyst in the heterogeneous photo-Fenton process. Catalyst loading of 0.5 g/L and hydrogen peroxide concentration of 13.5 mM yielded a remarkable color removal, accompanied by excellent catalyst stability. The decolorization of Orange II followed the pseudo-first-order kinetics for initial dye concentrations from 20 to 160 mg/L. The central composite design (CCD) based on the response surface methodology (RSM) was applied to evaluate the effects of several operating parameters, namely initial pH, catalyst loading and hydrogen peroxide concentration, on the decolorization efficiency. The RSM model was derived and the response surface plots were developed based on the results. Moreover, the main intermediate products were separated and identified using gas chromatography-mass spectrometry (GC-MS) and a possible degradation pathway was proposed accordingly. The acute toxicity experiments illustrated that the Daphnia magna immobilization rate continuously decreased during 150 min reaction, indicating that the effluent was suitable for sequential biological treatment.
Published: 2015
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46. Contemporaneous Imaging Comparisons of the Spotted Giant $\sigma$ Geminorum Using Interferometric, Spectroscopic, and Photometric Data

Author: Fabien Baron, Rachael M. Roettenbacher, Heidi Korhonen, Klaus G. Strassmeier, Thomas Hackman, Gregory W. Henry, John D. Monnier, T. ten Brummelaar, Gail Schaefer, Michael Weber, Robert O. Harmon, and Department of Physics
Subjects: Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Rotation, 01 natural sciences, CHARA array, ANDROMEDAE, stars: activity, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, LINE-DATA-BASE, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, CHARA ARRAY, Physics, binaries: close, 010308 nuclear & particles physics, Starspot, CYCLES, Astrophysics::Instrumentation and Methods for Astrophysics, stars: individual (sigma Geminorum), Astronomy and Astrophysics, 115 Astronomy, Space science, stars: imaging, stars: variables: general, Stars, Interferometry, STELLAR SURFACES, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, TESTS, ROTATION, Astrophysics::Earth and Planetary Astrophysics, Rapid rotation, STARS
Abstract: Nearby, active stars with relatively rapid rotation and large starspot structures offer the opportunity to compare interferometric, spectroscopic, and photometric imaging techniques. In this paper, we image a spotted star with three different methods for the first time. The giant primary star of the RS Canum Venaticorum binary $\sigma$ Geminorum ($\sigma$ Gem) was imaged for two epochs of interferometric, high-resolution spectroscopic, and photometric observations. The light curves from the reconstructions show good agreement with the observed light curves, supported by the longitudinally-consistent spot features on the different maps. However, there is strong disagreement in the spot latitudes across the methods., Comment: Accepted to ApJ, 19 pages, 16 figures, 5 tables
Published: 2017

47. Structure of Herbig AeBe disks at the milliarcsecond scale: A statistical survey in the H band using PIONIER-VLTI

Author: Olivier Absil, Michel Tallon, Laurent Jocou, Attila Juhasz, Bernard Lazareff, Alain Delboulbé, Karine Perraut, J.-B. Le Bouquin, Wesley A. Traub, John D. Monnier, Andrea Isella, François Ménard, Jacques Kluska, Myriam Benisty, T. Moulin, Stefan Kraus, Rafael Millan-Gabet, R. Lachaume, Gilles Duvert, Fabien Baron, S. Rochat, G. Zins, C. Pinte, Fabien Malbet, Chris Koen, W. F. Thi, Éric Thiébaut, Ferréol Soulez, Jean-Phillipe Berger, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), University of the Western Cape, Max-Planck-Institut für Extraterrestrische Physik (MPE), Université de Liège, Georgia State University, University System of Georgia (USG), INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), Institute of Astronomy [Cambridge], University of Cambridge [UK] (CAM), University of Exeter, California Institute of Technology (CALTECH), University of Michigan [Ann Arbor], University of Michigan System, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), California Institute of Technology (CALTECH)-NASA, University of the Western Cape (UWC), and École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL)
Subjects: FOS: Physical sciences, Scale (descriptive set theory), Context (language use), Astrophysics, stars: pre-main sequence, Ring (chemistry), 01 natural sciences, circumstellar matter, techniques: photometric, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, stars: variables: T Tauri, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Herbig Ae/Be, Astronomy and Astrophysics, Radius, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Interferometry, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, techniques: interferometric, Sublimation (phase transition), Halo, Astrophysics::Earth and Planetary Astrophysics
Abstract: Context. It is now generally accepted that the near-infrared excess of Herbig AeBe stars originates in the dust of a circumstellar disk. Aims. The aims of this article are to infer the radial and vertical structure of these disks at scales of order one au, and the properties of the dust grains. Methods. The program objects (51 in total) were observed with the H-band (1.6micron) PIONIER/VLTI interferometer. The largest baselines allowed us to resolve (at least partially) structures of a few tenths of an au at typical distances of a few hundred parsecs. Dedicated UBVRIJHK photometric measurements were also obtained. Spectral and 2D geometrical parameters are extracted via fits of a few simple models: ellipsoids and broadened rings with azimuthal modulation. Model bias is mitigated by parallel fits of physical disk models. Sample statistics were evaluated against similar statistics for the physical disk models to infer properties of the sample objects as a group. Results. We find that dust at the inner rim of the disk has a sublimation temperature Tsub~1800K. A ring morphology is confirmed for approximately half the resolved objects; these rings are wide delta_r>=0.5. A wide ring favors a rim that, on the star-facing side, looks more like a knife edge than a doughnut. The data are also compatible with a the combination of a narrow ring and an inner disk of unspecified nature inside the dust sublimation radius. The disk inner part has a thickness z/r~0.2, flaring to z/r~0.5 in the outer part. We confirm the known luminosity-radius relation; a simple physical model is consistent with both the mean luminosity-radius relation and the ring relative width; however, a significant spread around the mean relation is present. In some of the objects we find a halo component, fully resolved at the shortest interferometer spacing, that is related to the HAeBe class., 41 pages. 23 figures. Four appendices
Published: 2017
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48. Asymmetries on red giant branch surfaces from CHARA/MIRC optical interferometry

Author: Martin Asplund, Luca Fossati, John D. Monnier, Miguel Montargès, R. Ligi, Guy Perrin, Nicolas Nardetto, Remo Collet, T. ten Brummelaar, Pierre Kervella, Gail H. Schaefer, Denis Mourard, Andrea Chiavassa, Zazralt Magic, Lionel Bigot, Ryan Norris, Fabien Baron, Laboratoire d'Astrophysique de Marseille (LAM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)
Subjects: individual: HD 197989 [stars], stars: individual: HD 161096, stars: individual: HD 197989, FOS: Physical sciences, Context (language use), Astrophysics, 01 natural sciences, 010309 optics, 0103 physical sciences, stars: atmospheres, individual: HD 189276 [stars], Spectroscopy, 010303 astronomy & astrophysics, infrared: stars, Solar and Stellar Astrophysics (astro-ph.SR), atmospheres [stars], Physics, stars [infrared], Cosmic distance ladder, Astronomy and Astrophysics, individual: HD 161096 [stars], Galaxy, interferometric [techniques], stars: individual: HD 189276, Red-giant branch, Stars, Interferometry, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, techniques: interferometric, RGB color model, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Context. Red giant branch (RGB) stars are very bright objects in galaxies and are often used as standard candles. Interferometry is the ideal tool to characterize the dynamics and morphology of their atmospheres. Aims. We aim at precisely characterising the surface dynamics of a sample of RGB stars. Methods. We obtained interferometric observations for three RGB stars with the MIRC instrument mounted at the CHARA interfer- ometer. We looked for asymmetries on the stellar surfaces using limb-darkening models. Results. We measured the apparent diameters of HD197989 (Epsilon Cyg) = 4.61+-0.02 mas, HD189276 (HR7633) = 2.95+-0.01 mas, and HD161096 (Beta Oph) = 4.43+-0.01 mas. We detected departures from the centrosymmetric case for all three stars with the tendency of a greater effect for lower logg of the sample. We explored the causes of this signal and conclude that a possible explanation to the interferometric signal is the convection-related and/or the magnetic-related surface activity. However, it is necessary to monitor these stars with new observations, possibly coupled with spectroscopy, in order to firmly establish the cause., Accepted for publication as a Letter in Astronomy and Astrophysics, section 1. Letters to the Editor. The official date of acceptance is 06/03/2017
Published: 2017
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49. Dusty disk winds at the sublimation rim of the highly inclined, low mass young stellar object SU Aurigae

Author: Laszlo Sturmann, John D. Monnier, Jacques Kluska, Brian Kloppenborg, Judit Sturmann, Aaron Labdon, Stefan Kraus, Fabien Baron, Rafael Millan-Gabet, Joshua Eisner, Claire L. Davies, T. ten Brummelaar, Alexander Kreplin, and Tim J. Harries
Subjects: 010504 meteorology & atmospheric sciences, Young stellar object, Astrophysics, Astronomy & Astrophysics, Computer Science::Digital Libraries, 01 natural sciences, CHARA array, Planet, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, Science & Technology, protoplanetary disks, Astrophysics::Instrumentation and Methods for Astrophysics, MAGNETIC-FIELD, INNER RIM, Astronomy and Astrophysics, Scale height, Position angle, CATALOG, Physics::History of Physics, interferometric [techniques], MODEL, T Tauri star, Stars, radiative transfer, Space and Planetary Science, Physical Sciences, Astrophysics::Earth and Planetary Astrophysics, variables: T Tauri, Herbig Ae/Be [stars], T-TAURI, STARS
Abstract: Context. T Tauri stars are low-mass young stars whose disks provide the setting for planet formation. Despite this, their structure is poorly understood. We present new infrared interferometric observations of the SU Aurigae circumstellar environment that offer resolution that is three times higher and a better baseline position angle coverage than previous observations. Aims. We aim to investigate the characteristics of the circumstellar material around SU Aur, constrain the disk geometry, composition and inner dust rim structure. Methods. The CHARA array offers unique opportunities for long baseline observations, with baselines up to 331 m. Using the CLIMB three-telescope combiner in the K-band allows us to measure visibilities as well as closure phase. We undertook image reconstruction for model-independent analysis, and fitted geometric models such as Gaussian and ring distributions. Additionally, the fitting of radiative transfer models constrain the physical parameters of the disk. For the first time, a dusty disk wind is introduced to the radiative transfer code TORUS to model protoplanetary disks. Our implementation is motivated by theoretical models of dusty disk winds, where magnetic field lines drive dust above the disk plane close to the sublimation zone. Results. Image reconstruction reveals an inclined disk with slight asymmetry along its minor-axis, likely due to inclination effects obscuring the inner disk rim through absorption of incident star light on the near-side and thermal re-emission and scattering of the far-side. Geometric modelling of a skewed ring finds the inner rim at 0.17 ± 0.02 au with an inclination of 50.9 ± 1.0° and minor axis position angle 60.8 ± 1.2°. Radiative transfer modelling shows a flared disk with an inner radius at 0.18 au which implies a grain size of 0.4 μm assuming astronomical silicates and a scale height of 15.0 at 100 au. Among the tested radiative transfer models, only the dusty disk wind successfully accounts for the K-band excess by introducing dust above the mid-plane.
Published: 2019
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50. Revisiting the cation mass-valence sum approach to assigning infrared OH-bands in dioctahedral smectites in the light of new data from synthetic Ga-Fe3+ smectites

Author: Sabine Petit, Fabien Baron, Olivier Grauby, Alain Decarreau, Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), and Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Poitiers-Institut de Chimie du CNRS (INC)
Subjects: Ionic radius, Valence (chemistry), Infrared, Chemistry, Inorganic chemistry, Infrared spectroscopy, 020101 civil engineering, 02 engineering and technology, 010502 geochemistry & geophysics, 01 natural sciences, 0201 civil engineering, Crystallography, Octahedron, Absorption band, [CHIM]Chemical Sciences, Clay minerals, Spectroscopy, 0105 earth and related environmental sciences
Abstract: International audience; A series of pure Ga-Fe3+ smectites were synthesized at 180 degrees C in order to complete IR data in the Al-Ga-Fe3+ system. MIR and NIR data from natural and synthetic smectites in the Al-Fe3+, Al-Ga and Fe3+-Ga chemical series exemplified a case where some nu OH, delta OH and (nu + delta) OH band positions did not follow the relation: nu OH (cm(-1))=(1/2 pi c)*(k(OH)/mu(OH))(1/2). This relation is often used to approximate the position of the OH vibration bands from the reduced masses of octahedral cations linked to hydroxyls in clay minerals. In this study, better relations were established between the wavenumbers of the OH absorption band of smectites and the average ionic radius of neighboring octahedral cations. Similar trends were established previously for M-(OH)(2) hydroxides (G.W. Brindley, C. Kao, Phys. Chem.Miner. 10 (1984) 187-191) suggesting a possible generalization of a link between OH frequencies in IR spectra and the average ionic radii of neighboring octahedral cations for hydroxylated minerals. (C) 2016 Elsevier B.V. All rights reserved.
Published: 2016
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