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V J S Bejar - One of the best experts on this subject based on the ideXlab platform.
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search for free floating planetary mass objects in the Pleiades
Astronomy and Astrophysics, 2014Co-Authors: M Zapatero R Osorio, G. Bihain, V J S Bejar, Th. Henning, M Galvez C Ortiz, C A L Bailerjones, R Rebolo, S BoudreaultAbstract:Aims. We aim at identifying the least massive population of the solar metallicity, young (120 Myr), nearby (133.5 pc) Pleiades star cluster with the ultimate goal of understanding the physical properties of intermediate-age, free-floating, low-mass brown dwarfs and giant planetary-mass objects, and deriving the cluster substellar mass function across the deuterium-burning mass limit at ≈0.012 M� . Methods. We performed a deep photometric and astrometric J -a ndH-band survey covering an area of ∼0.8 deg 2 in the Pleiades cluster. The images with completeness and limiting magnitudes of J,H ≈ 20. 2a nd≈21.5 mag were acquired ∼9 yr apart, allowing us to derive proper motions with a typical precision of ± 6m as yr −1 . For the cluster distance and age, the survey is sensitive to Pleiades members with masses in the interval ≈0.2−0.008 M� . J -a ndH-band data were complemented with Z, K, and mid-infrared magnitudes up to 4.6 μm coming from the UKIRT Infrared Deep Sky Survey (UKIDSS), the WISE catalog, and follow-up observations of our own. Pleiades member candidates were selected to have proper motions compatible with that of the cluster, and colors following the known Pleiades sequence in the interval J = 15.5−18. 8m ag, andZUKIDSS − J ≥ 2. 3m ag orZ nondetections for J > 18. 8m ag. Results. We found a neat sequence of astrometric and photometric Pleiades substellar member candidates with two or more proper motion measurements and with magnitudes and masses in the intervals J = 15.5−21.2 mag and ≈0.072−0.008 M� . The faintest objects show very red near- and mid-infrared colors exceeding those of field high-gravity dwarfs by ≥0.5 mag. This agrees with the reported properties of field young L-type dwarfs and giant planets orbiting stars of ages of ∼100 Myr. The Pleiades photometric sequence does not show any color turn-over because of the presence of photospheric methane absorption down to J = 20.3 mag, which is about 1 mag fainter than predicted by the combination of evolutionary models and colors computed from model atmospheres. The astrometric data suggest that Pleiades brown dwarfs have a proper motion dispersion of 6.4−7.5 mas yr −1 , and are dynamically relaxed at the age of the cluster. The Pleiades mass function extends down to the deuterium burning-mass threshold, with a slope fairly similar to that of other young star clusters and stellar associations. The new discoveries may become benchmark objects for interpreting the observations of the emerging young ultracool population and giant planets around stars in the solar neighborhood.
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search for free floating planetary mass objects in the Pleiades
arXiv: Solar and Stellar Astrophysics, 2014Co-Authors: M Zapatero R Osorio, G. Bihain, V J S Bejar, Th. Henning, M Galvez C Ortiz, C A L Bailerjones, R Rebolo, S BoudreaultAbstract:(Abridged) We aim at identifying the least massive population of the solar metallicity, young (120 Myr), nearby (133.5 pc) Pleiades star cluster with the ultimate goal of understanding the physical properties of intermediate-age, free-floating, low-mass brown dwarfs and giant planetary-mass objects, and deriving the cluster substellar mass function across the deuterium-burning mass limit at ~0.012 Msol. We performed a deep photometric and astrometric J- and H-band survey covering an area of ~0.8 deg^2. The images with completeness and limiting magnitudes of J,H ~ 20.2 and ~ 21.5 mag were acquired ~9 yr apart (proper motion precision of +/-6 mas/yr). J- and H-band data were complemented with Z, K, and mid-infrared magnitudes up to 4.6 micron coming from UKIDSS, WISE, and follow-up observations of our own. Pleiades member candidates were selected to have proper motions compatible with that of the cluster, and colors following the known Pleiades sequence in the interval J = 15.5-8.8 mag, and Z_UKIDSS - J > 2.3 mag or Z nondetections for J > 18.8 mag. We found a neat sequence of astrometric and photometric Pleiades substellar member candidates in the intervals J = 15.5-21.2 mag and ~0.072-0.008 Msol. The faintest objects show very red near- and mid-infrared colors exceeding those of field high-gravity dwarfs by >0.5 mag. The Pleiades photometric sequence does not show any color turn-over because of the presence of photospheric methane absorption down to J = 20.3 mag, which is about 1 mag fainter than predicted by the color-computed models. Pleiades brown dwarfs have a proper motion dispersion of 6.4-7.5 mas/yr and are dynamically relaxed at the age of the cluster. The Pleiades mass function extends down to the deuterium burning-mass threshold, with a slope fairly similar to that of other young star clusters and stellar associations.
R Rebolo - One of the best experts on this subject based on the ideXlab platform.
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search for free floating planetary mass objects in the Pleiades
Astronomy and Astrophysics, 2014Co-Authors: M Zapatero R Osorio, G. Bihain, V J S Bejar, Th. Henning, M Galvez C Ortiz, C A L Bailerjones, R Rebolo, S BoudreaultAbstract:Aims. We aim at identifying the least massive population of the solar metallicity, young (120 Myr), nearby (133.5 pc) Pleiades star cluster with the ultimate goal of understanding the physical properties of intermediate-age, free-floating, low-mass brown dwarfs and giant planetary-mass objects, and deriving the cluster substellar mass function across the deuterium-burning mass limit at ≈0.012 M� . Methods. We performed a deep photometric and astrometric J -a ndH-band survey covering an area of ∼0.8 deg 2 in the Pleiades cluster. The images with completeness and limiting magnitudes of J,H ≈ 20. 2a nd≈21.5 mag were acquired ∼9 yr apart, allowing us to derive proper motions with a typical precision of ± 6m as yr −1 . For the cluster distance and age, the survey is sensitive to Pleiades members with masses in the interval ≈0.2−0.008 M� . J -a ndH-band data were complemented with Z, K, and mid-infrared magnitudes up to 4.6 μm coming from the UKIRT Infrared Deep Sky Survey (UKIDSS), the WISE catalog, and follow-up observations of our own. Pleiades member candidates were selected to have proper motions compatible with that of the cluster, and colors following the known Pleiades sequence in the interval J = 15.5−18. 8m ag, andZUKIDSS − J ≥ 2. 3m ag orZ nondetections for J > 18. 8m ag. Results. We found a neat sequence of astrometric and photometric Pleiades substellar member candidates with two or more proper motion measurements and with magnitudes and masses in the intervals J = 15.5−21.2 mag and ≈0.072−0.008 M� . The faintest objects show very red near- and mid-infrared colors exceeding those of field high-gravity dwarfs by ≥0.5 mag. This agrees with the reported properties of field young L-type dwarfs and giant planets orbiting stars of ages of ∼100 Myr. The Pleiades photometric sequence does not show any color turn-over because of the presence of photospheric methane absorption down to J = 20.3 mag, which is about 1 mag fainter than predicted by the combination of evolutionary models and colors computed from model atmospheres. The astrometric data suggest that Pleiades brown dwarfs have a proper motion dispersion of 6.4−7.5 mas yr −1 , and are dynamically relaxed at the age of the cluster. The Pleiades mass function extends down to the deuterium burning-mass threshold, with a slope fairly similar to that of other young star clusters and stellar associations. The new discoveries may become benchmark objects for interpreting the observations of the emerging young ultracool population and giant planets around stars in the solar neighborhood.
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search for free floating planetary mass objects in the Pleiades
arXiv: Solar and Stellar Astrophysics, 2014Co-Authors: M Zapatero R Osorio, G. Bihain, V J S Bejar, Th. Henning, M Galvez C Ortiz, C A L Bailerjones, R Rebolo, S BoudreaultAbstract:(Abridged) We aim at identifying the least massive population of the solar metallicity, young (120 Myr), nearby (133.5 pc) Pleiades star cluster with the ultimate goal of understanding the physical properties of intermediate-age, free-floating, low-mass brown dwarfs and giant planetary-mass objects, and deriving the cluster substellar mass function across the deuterium-burning mass limit at ~0.012 Msol. We performed a deep photometric and astrometric J- and H-band survey covering an area of ~0.8 deg^2. The images with completeness and limiting magnitudes of J,H ~ 20.2 and ~ 21.5 mag were acquired ~9 yr apart (proper motion precision of +/-6 mas/yr). J- and H-band data were complemented with Z, K, and mid-infrared magnitudes up to 4.6 micron coming from UKIDSS, WISE, and follow-up observations of our own. Pleiades member candidates were selected to have proper motions compatible with that of the cluster, and colors following the known Pleiades sequence in the interval J = 15.5-8.8 mag, and Z_UKIDSS - J > 2.3 mag or Z nondetections for J > 18.8 mag. We found a neat sequence of astrometric and photometric Pleiades substellar member candidates in the intervals J = 15.5-21.2 mag and ~0.072-0.008 Msol. The faintest objects show very red near- and mid-infrared colors exceeding those of field high-gravity dwarfs by >0.5 mag. The Pleiades photometric sequence does not show any color turn-over because of the presence of photospheric methane absorption down to J = 20.3 mag, which is about 1 mag fainter than predicted by the color-computed models. Pleiades brown dwarfs have a proper motion dispersion of 6.4-7.5 mas/yr and are dynamically relaxed at the age of the cluster. The Pleiades mass function extends down to the deuterium burning-mass threshold, with a slope fairly similar to that of other young star clusters and stellar associations.
Shawn M Landry - One of the best experts on this subject based on the ideXlab platform.
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assessing the potential of multi seasonal high resolution Pleiades satellite imagery for mapping urban tree species
International Journal of Applied Earth Observation and Geoinformation, 2018Co-Authors: Shawn M LandryAbstract:Abstract This study evaluated the potential of five seasonal high resolution Pleiades satellite images for improving urban tree species classification in the City of Tampa, FL, USA. We assessed and compared the capabilities of individual and combined Pleiades images acquired during different seasons for classifying the urban tree species to understand the seasonal effect on tree species mapping accuracy. The seven species and groups included sand live oak (Quercus geminata), laurel oak (Q. laurifolia), live oak (Q. virginiana), pine (species group), palm (species group), camphor (Cinnamomum camphora), and magnolia (Magnolia grandiflora). A multi-level classification system was adopted to classify image objects of the tree species and groups. Species classification performance was compared between the five individual seasonal Pleiades images, between two combined dry-wet season images, and between the optimal single season and combined dry-wet season image data. Shade image objects were spectrally normalized to similar sunlit image objects. The tree species fraction features were extracted from the seasonal images using the Mixture Tuned Matching Filtering approach and used as additional features to a set of spectral and spatial/textural features. Random Forest, Support Vector Machine and Linear Discriminant Analysis classifiers were used to classify the seven tree species and groups with image objects features. The experimental results indicate significantly improved tree species mapping accuracies using late spring season (April) image compared to all other seasonal images (p
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assessing the potential of multi seasonal high resolution Pleiades satellite imagery for mapping urban tree species
International Workshop on Earth Observation and Remote Sensing Applications, 2018Co-Authors: Shawn M LandryAbstract:The multi-season Pleiades image data were compared and analyzed for their capabilities of classifying and mapping the seven urban forest tree species in the City of Tampa, FL, USA to understand the seasonal effect on tree species classification accuracy. The seven species and groups included sand live oak (Quercus geminata), laurel oak (Q. laurifolia), live oak (Q. virginiana), pine (species group), palm (species group), camphor (Cinnamomum camphora), and magnolia (Magnolia grandiflora). A multi-level classification system was adopted to classify image objects of the tree species. Shade image objects (IOs) were spectrally normalized to similar sunlit IOs, and the tree species fractions were extracted from the seasonal images using a spectral unmixing approach and used as additional features. Using selected features extracted from the five individual season and the two dry-wet season combined Pleiades images, tree species were identified and mapped using a random Forest, support vector machines and a linear discriminant analysis classifiers. The experimental results indicate significantly improved tree species mapping accuracies using late spring season (April) image compared to all other seasonal images (p<0.01), and combined dry-wet season images performed even better. Results suggest a significant seasonal effect on tree species classification. The novel significance of this study was to demonstrate the potential of multi-season Pleiades imagery in improving urban tree species mapping. Therefore, in practice, it is important to choose appropriate seasonal remote sensing data for mapping tree species.
M Zapatero R Osorio - One of the best experts on this subject based on the ideXlab platform.
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search for free floating planetary mass objects in the Pleiades
Astronomy and Astrophysics, 2014Co-Authors: M Zapatero R Osorio, G. Bihain, V J S Bejar, Th. Henning, M Galvez C Ortiz, C A L Bailerjones, R Rebolo, S BoudreaultAbstract:Aims. We aim at identifying the least massive population of the solar metallicity, young (120 Myr), nearby (133.5 pc) Pleiades star cluster with the ultimate goal of understanding the physical properties of intermediate-age, free-floating, low-mass brown dwarfs and giant planetary-mass objects, and deriving the cluster substellar mass function across the deuterium-burning mass limit at ≈0.012 M� . Methods. We performed a deep photometric and astrometric J -a ndH-band survey covering an area of ∼0.8 deg 2 in the Pleiades cluster. The images with completeness and limiting magnitudes of J,H ≈ 20. 2a nd≈21.5 mag were acquired ∼9 yr apart, allowing us to derive proper motions with a typical precision of ± 6m as yr −1 . For the cluster distance and age, the survey is sensitive to Pleiades members with masses in the interval ≈0.2−0.008 M� . J -a ndH-band data were complemented with Z, K, and mid-infrared magnitudes up to 4.6 μm coming from the UKIRT Infrared Deep Sky Survey (UKIDSS), the WISE catalog, and follow-up observations of our own. Pleiades member candidates were selected to have proper motions compatible with that of the cluster, and colors following the known Pleiades sequence in the interval J = 15.5−18. 8m ag, andZUKIDSS − J ≥ 2. 3m ag orZ nondetections for J > 18. 8m ag. Results. We found a neat sequence of astrometric and photometric Pleiades substellar member candidates with two or more proper motion measurements and with magnitudes and masses in the intervals J = 15.5−21.2 mag and ≈0.072−0.008 M� . The faintest objects show very red near- and mid-infrared colors exceeding those of field high-gravity dwarfs by ≥0.5 mag. This agrees with the reported properties of field young L-type dwarfs and giant planets orbiting stars of ages of ∼100 Myr. The Pleiades photometric sequence does not show any color turn-over because of the presence of photospheric methane absorption down to J = 20.3 mag, which is about 1 mag fainter than predicted by the combination of evolutionary models and colors computed from model atmospheres. The astrometric data suggest that Pleiades brown dwarfs have a proper motion dispersion of 6.4−7.5 mas yr −1 , and are dynamically relaxed at the age of the cluster. The Pleiades mass function extends down to the deuterium burning-mass threshold, with a slope fairly similar to that of other young star clusters and stellar associations. The new discoveries may become benchmark objects for interpreting the observations of the emerging young ultracool population and giant planets around stars in the solar neighborhood.
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search for free floating planetary mass objects in the Pleiades
arXiv: Solar and Stellar Astrophysics, 2014Co-Authors: M Zapatero R Osorio, G. Bihain, V J S Bejar, Th. Henning, M Galvez C Ortiz, C A L Bailerjones, R Rebolo, S BoudreaultAbstract:(Abridged) We aim at identifying the least massive population of the solar metallicity, young (120 Myr), nearby (133.5 pc) Pleiades star cluster with the ultimate goal of understanding the physical properties of intermediate-age, free-floating, low-mass brown dwarfs and giant planetary-mass objects, and deriving the cluster substellar mass function across the deuterium-burning mass limit at ~0.012 Msol. We performed a deep photometric and astrometric J- and H-band survey covering an area of ~0.8 deg^2. The images with completeness and limiting magnitudes of J,H ~ 20.2 and ~ 21.5 mag were acquired ~9 yr apart (proper motion precision of +/-6 mas/yr). J- and H-band data were complemented with Z, K, and mid-infrared magnitudes up to 4.6 micron coming from UKIDSS, WISE, and follow-up observations of our own. Pleiades member candidates were selected to have proper motions compatible with that of the cluster, and colors following the known Pleiades sequence in the interval J = 15.5-8.8 mag, and Z_UKIDSS - J > 2.3 mag or Z nondetections for J > 18.8 mag. We found a neat sequence of astrometric and photometric Pleiades substellar member candidates in the intervals J = 15.5-21.2 mag and ~0.072-0.008 Msol. The faintest objects show very red near- and mid-infrared colors exceeding those of field high-gravity dwarfs by >0.5 mag. The Pleiades photometric sequence does not show any color turn-over because of the presence of photospheric methane absorption down to J = 20.3 mag, which is about 1 mag fainter than predicted by the color-computed models. Pleiades brown dwarfs have a proper motion dispersion of 6.4-7.5 mas/yr and are dynamically relaxed at the age of the cluster. The Pleiades mass function extends down to the deuterium burning-mass threshold, with a slope fairly similar to that of other young star clusters and stellar associations.
Davy J Kirkpatrick - One of the best experts on this subject based on the ideXlab platform.
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keck spectra of Pleiades brown dwarf candidates and a precise determination of the lithium depletion edge in the Pleiades
The Astrophysical Journal, 1998Co-Authors: John R Stauffer, Greg Schultz, Davy J KirkpatrickAbstract:We have obtained intermediate resolution spectra of 11 candidate brown dwarf members of the Pleiades open cluster using the Keck II telescope and Low-Resolution Imaging Spectrograph. Our primary goal was to determine the location of the "lithium depletion edge" in the Pleiades and hence to derive a precise age for the cluster. All but one of our 11 program objects have radial velocities appropriate for Pleiades members, have moderately strong Hα emission, and have spectral types M6-M8.5 as expected from their (R - I)C colors. We have constructed a color-magnitude diagram for the faint end of the Pleiades main sequence, including only stars for which high signal-to-noise spectra in the region of the lithium 6708 A absorption line have been obtained. These data allow us to accurately determine the Pleiades single-star lithium depletion edge at IC0 = 17.80, (R - I)C0 = 2.20, spectral type M6.5. By reference to theoretical evolutionary models, this converts fairly directly into an age for the Pleiades of τ = 125 Myr. This is significantly older than the age that is normally quoted, but does agree with some other recent estimates.
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keck spectra of Pleiades brown dwarf candidates and a precise determination of the lithium depletion edge in the Pleiades
arXiv: Astrophysics, 1998Co-Authors: John R Stauffer, Greg Schultz, Davy J KirkpatrickAbstract:We have obtained intermediate resolution spectra of eleven candidate brown dwarf members of the Pleiades open cluster using the Keck II telescope and LRIS spectrograph. Our primary goal was to determine the location of the "lithium depletion edge" in the Pleiades and hence to derive a precise age for the cluster. All but one of our 11 program objects have radial velocities appropriate for Pleiades members, have moderately strong H alpha emission, and have spectral types M6 to M8.5, as expected for their (R-I) colors. We have constructed a color-magnitude diagram for the faint end of the Pleiades main sequence, including only stars for which high S/N spectra in the region of the lithium 6708 Angstrom absorption line have been obtained. These data allow us to accurately determine the Pleiades single-star lithium depletion edge at I(c0) = 17.80, R-I(c0) = 2.20, spectral type = M6.5. By reference to theoretical evolutionary models, this converts fairly directly into an age for the Pleiades of 125 Myr. This is significantly older than the age that is normally quoted, but does agree with some other recent estimates.
