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P M Visser - One of the best experts on this subject based on the ideXlab platform.
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fourier spectra from exoPlanets with polar caps and ocean glint
2015Co-Authors: P M Visser, F J Van De BultAbstract:The weak orbital-phase dependent reflection signal of an exoPlanet contains information on the Planet Surface, such as the distribution of continents and oceans on terrestrial Planets. This light curve is usually studied in the time domain, but because the signal from a stationary Surface is (quasi)periodic, analysis of the Fourier series may provide an alternative, complementary approach. We study Fourier spectra from reflected light curves for geometrically simple configurations. Depending on its atmospheric properties, a rotating Planet in the habitable zone could have circular polar ice caps. Tidally locked Planets, on the other hand, may have symmetric circular oceans facing the star. These cases are interesting because the high-albedo contrast at the sharp edges of the ice-sheets and the glint from the host star in the ocean may produce recognizable light curves with orbital periodicity, which could also be interpreted in the Fourier domain. We derive a simple general expression for the Fourier coefficients of a quasiperiodic light curve in terms of the albedo map of a Lambertian Planet Surface. Analytic expressions for light curves and their spectra are calculated for idealized situations, and dependence of spectral peaks on the key parameters inclination, obliquity, and cap size is studied.
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fourier spectra from exoPlanets with polar caps and ocean glint
2015Co-Authors: P M Visser, F J Van De BultAbstract:Context. The weak orbital-phase dependent reflection signal of an exoPlanet contains information on the Planet Surface, such as the distribution of continents and oceans on terrestrial Planets. This light curve is usually studied in the time domain, but because the signal from a stationary Surface is (quasi)periodic, analysis of the Fourier series may provide an alternative, complementary approach. Aims. We study Fourier spectra from reflected light curves for geometrically simple configurations. Depending on its atmospheric properties, a rotating Planet in the habitable zone could have circular polar ice caps. Tidally locked Planets, on the other hand, may have symmetric circular oceans facing the star. These cases are interesting because the high-albedo contrast at the sharp edges of the ice-sheets and the glint from the host star in the ocean may produce recognizable light curves with orbital periodicity, which could also be interpreted in the Fourier domain. Methods. We derive a simple general expression for the Fourier coefficients of a quasiperiodic light curve in terms of the albedo map of a Lambertian Planet Surface. Analytic expressions for light curves and their spectra are calculated for idealized situations, and dependence of the spectral peaks on the key parameters inclination, obliquity, and cap size is studied. Results. The ice-scattering and ocean glint contributions can be separated out, because the coefficients for glint are all positive, whereas ice sheets lead to even-numbered, higher harmonics. An in-view polar cap on a Planet without axial tilt only produces a single peak. The special situation of edge-on observation, which is important for Planets in transit, leads to the most pronounced spectral behavior. Then the respective spectra from Planets with a circumventing ocean, a circular ocean (eyeball world), polar caps, and rings, have characteristic power-law tails n−2, n−7/2, n−4, and (−1)n+1n−2. Conclusions. Promising recently discovered Planetary systems may be selected as candidates for long-term (multiyear) observation: their Fourier spectra could separate the different Planets and reveal or identify a water-covered Planet with polar caps.
F J Van De Bult - One of the best experts on this subject based on the ideXlab platform.
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fourier spectra from exoPlanets with polar caps and ocean glint
2015Co-Authors: P M Visser, F J Van De BultAbstract:Context. The weak orbital-phase dependent reflection signal of an exoPlanet contains information on the Planet Surface, such as the distribution of continents and oceans on terrestrial Planets. This light curve is usually studied in the time domain, but because the signal from a stationary Surface is (quasi)periodic, analysis of the Fourier series may provide an alternative, complementary approach. Aims. We study Fourier spectra from reflected light curves for geometrically simple configurations. Depending on its atmospheric properties, a rotating Planet in the habitable zone could have circular polar ice caps. Tidally locked Planets, on the other hand, may have symmetric circular oceans facing the star. These cases are interesting because the high-albedo contrast at the sharp edges of the ice-sheets and the glint from the host star in the ocean may produce recognizable light curves with orbital periodicity, which could also be interpreted in the Fourier domain. Methods. We derive a simple general expression for the Fourier coefficients of a quasiperiodic light curve in terms of the albedo map of a Lambertian Planet Surface. Analytic expressions for light curves and their spectra are calculated for idealized situations, and dependence of the spectral peaks on the key parameters inclination, obliquity, and cap size is studied. Results. The ice-scattering and ocean glint contributions can be separated out, because the coefficients for glint are all positive, whereas ice sheets lead to even-numbered, higher harmonics. An in-view polar cap on a Planet without axial tilt only produces a single peak. The special situation of edge-on observation, which is important for Planets in transit, leads to the most pronounced spectral behavior. Then the respective spectra from Planets with a circumventing ocean, a circular ocean (eyeball world), polar caps, and rings, have characteristic power-law tails n−2, n−7/2, n−4, and (−1)n+1n−2. Conclusions. Promising recently discovered Planetary systems may be selected as candidates for long-term (multiyear) observation: their Fourier spectra could separate the different Planets and reveal or identify a water-covered Planet with polar caps.
F J Van De Bult - One of the best experts on this subject based on the ideXlab platform.
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fourier spectra from exoPlanets with polar caps and ocean glint
2015Co-Authors: P M Visser, F J Van De BultAbstract:The weak orbital-phase dependent reflection signal of an exoPlanet contains information on the Planet Surface, such as the distribution of continents and oceans on terrestrial Planets. This light curve is usually studied in the time domain, but because the signal from a stationary Surface is (quasi)periodic, analysis of the Fourier series may provide an alternative, complementary approach. We study Fourier spectra from reflected light curves for geometrically simple configurations. Depending on its atmospheric properties, a rotating Planet in the habitable zone could have circular polar ice caps. Tidally locked Planets, on the other hand, may have symmetric circular oceans facing the star. These cases are interesting because the high-albedo contrast at the sharp edges of the ice-sheets and the glint from the host star in the ocean may produce recognizable light curves with orbital periodicity, which could also be interpreted in the Fourier domain. We derive a simple general expression for the Fourier coefficients of a quasiperiodic light curve in terms of the albedo map of a Lambertian Planet Surface. Analytic expressions for light curves and their spectra are calculated for idealized situations, and dependence of spectral peaks on the key parameters inclination, obliquity, and cap size is studied.
Mihkel Pajusalu - One of the best experts on this subject based on the ideXlab platform.
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low albedo Surfaces of lava worlds
2020Co-Authors: Zahra Essack, Sara Seager, Mihkel PajusaluAbstract:Hot super Earths are exoPlanets with short orbital periods ($ $ 0.4) in the Kepler band (420-900 nm). We are motivated to determine whether reflection from molten lava and quenched glasses (a product of rapidly cooled lava) on the Surfaces of hot super Earths contributes to the observationally inferred high geometric albedos. We experimentally measure reflection from rough and smooth textured quenched glasses of both basalt and feldspar melts. For lava reflectance values, we use specular reflectance values of molten silicates from non-crystalline solids literature. Integrating the empirical glass reflectance function and non-crystalline solids reflectance values over the dayside Surface of the exoPlanet at secondary eclipse yields an upper limit for the albedo of a lava-quenched glass Planet Surface of $\sim $0.1. We conclude that lava Planets with solid (quenched glass) or liquid (lava) Surfaces have low albedos. The high albedos of some hot super Earths are most likely explained by atmospheres with reflective clouds (or, for a narrow range of parameter space, possibly Ca/Al oxide melt Surfaces). Lava Planet candidates in TESS data can be identified for follow-up observations and future characterization.
Laurent Dufossé - One of the best experts on this subject based on the ideXlab platform.
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Biodiversity of Pigmented Fungi Isolated from Marine Environment in La Réunion Island, Indian Ocean: New Resources for Colored Metabolites
2017Co-Authors: Mireille Fouillaud, Mekala Venkatachalam, Melissa Llorente, Hélène Magalon, Pascale Cuet, Laurent DufosséAbstract:Marine ecosystems cover about 70% of the Planet Surface and are still an underexploited source of useful metabolites. Among microbes, filamentous fungi are captivating organisms used for the production of many chemical classes of secondary metabolites bound to be used in various fields of industrial application. The present study was focused on the collection, isolation, screening and genotyping of pigmented filamentous fungi isolated from tropical marine environments around La Réunion Island, Indian Ocean. About 150 micromycetes were revived and isolated from 14 marine samples (sediments, living corals, coral rubble, sea water and hard substrates) collected in four different locations. Forty-two colored fungal isolates belonging to 16 families, 25 genera and 31 species were further studied depending on their ability to produce pigments and thus subjected to molecular identification. From gene sequence analysis, the most frequently identified colored fungi belong to the widespread Penicillium, Talaromyces and Aspergillus genera in the family Trichocomaceae (11 species), then followed by the family Hypocreaceae (three species). This study demonstrates that marine biotopes in La Réunion Island, Indian Ocean, from coral reefs to underwater slopes of this volcanic island, shelter numerous species of micromycetes, from common or uncommon genera. This unstudied biodiversity comes along with the ability for some fungal marine inhabitants, to produce a range of pigments and hues.