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  • Other Sources  (3)
  • Astronomy  (2)
  • 551,9  (1)
  • 42.75
  • 2010-2014  (3)
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  • 1
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    Arsenic release from a natural rock under near-natural oxidizing conditions (2010)
    Details
    Publication Date: 2021-03-29
    Description: The solubilization of arsenic (As) from an ore material (native Arsenic [As, trig.] with Lollingite [FeAs2, rh.]) was characterized in leaching tests lasting for ≤ 99 days. The experiments were performed with materials of different particle sizes (≤ 2 mm), in different waters and under test conditions relevant to As mobilization at near surface contaminated sites. The impact of dolomite [CaMg(CO3)2], metallic iron (Fe0), and pyrite (FeS2) on As release was accessed. Two different types of batch experiments were conducted with a constant amount of the base material and different types of water (deionised, mineral, spring, and tap water). For comparison parallel experiments were conducted with 0.1M EDTA, 0.1M Na2CO3 and 0.1M H2SO4. The results indicated no significant effect of carbonate addition on As solubilization. Fe0 and FeS2 addition essentially slowed the initial As solubilization. H2SO4 was the sole leaching agent significantly influencing As solubilization from the base material. The general trend assuming that the smaller the particle size the quicker the As release was not strictly verified because in samples of smaller particle sizes (d 〈 0.063) As was partly oxidized to more stable species.
    Description: research
    Keywords: 551,9 ; VJF 000 ; Umweltgeochemie insgesamt
    Language: English
    Type: article , publishedVersion
    Format: 23 S.
    Format: application/pdf
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    CITATION GEO-LEO
  • 2
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    A Resolved Debris Disk Around the Candidate Planet-hosting Star HD 95086 (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Recently, a new planet candidate was discovered on direct images around the young (10-17 Myr) A-type star HD 95086. The strong infrared excess of the system indicates that, similar to HR8799, Beta Pic, and Fomalhaut, the star harbors a circumstellar disk. Aiming to study the structure and gas content of the HD 95086 disk, and to investigate its possible interaction with the newly discovered planet, here we present new optical, infrared, and millimeter observations. We detected no CO emission, excluding the possibility of an evolved gaseous primordial disk. Simple blackbody modeling of the spectral energy distribution suggests the presence of two spatially separate dust belts at radial distances of 6 and 64 AU. Our resolved images obtained with the Herschel Space Observatory reveal a characteristic disk size of approx. 6.0 5.4 (540 490 AU) and disk inclination of approx 25 deg. Assuming the same inclination for the planet candidate's orbit, its reprojected radial distance from the star is 62 AU, very close to the blackbody radius of the outer cold dust ring. The structure of the planetary system at HD 95086 resembles the one around HR8799. Both systems harbor a warm inner dust belt and a broad colder outer disk and giant planet(s) between the two dusty regions. Modeling implies that the candidate planet can dynamically excite the motion of planetesimals even out to 270 AU via their secular perturbation if its orbital eccentricity is larger than about 0.4. Our analysis adds a new example to the three known systems where directly imaged planet(s) and debris disks coexist.
    Keywords: Astronomy
    Type: GSFC-E-DAA-TN12417 , The Astrophysical Journal Letters; 51; 2; L51
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    NASA TECHNICAL REPORTS
  • 3
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    Spiral Arms in the Asymmetrically Illuminated Disk of MWC 758 and Constraints on Giant Planets (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We present the first near-IR scattered light detection of the transitional disk associated with the Herbig Ae star MWC 758 using data obtained as part of the Strategic Exploration of Exoplanets and Disks with Subaru, and 1.1 micrometer Hubble Space Telescope/NICMOS data. While submillimeter studies suggested there is a dust-depleted cavity with r = 0".35, we find scattered light as close as 0".1 (20-28 AU) from the star, with no visible cavity at H, K', or Ks . We find two small-scaled spiral structures that asymmetrically shadow the outer disk. We model one of the spirals using spiral density wave theory, and derive a disk aspect ratio of h approximately 0.18, indicating a dynamically warm disk. If the spiral pattern is excited by a perturber, we estimate its mass to be 5(exp +3)(sub -4) M(sub J), in the range where planet filtration models predict accretion continuing onto the star. Using a combination of non-redundant aperture masking data at L' and angular differential imaging with Locally Optimized Combination of Images at K' and Ks , we exclude stellar or massive brown dwarf companions within 300 mas of the Herbig Ae star, and all but planetary mass companions exterior to 0".5. We reach 5 sigma contrasts limiting companions to planetary masses, 3-4 M(sub J) at 1".0 and 2 M(sub J) at 1".55, using the COND models. Collectively, these data strengthen the case for MWC 758 already being a young planetary system.
    Keywords: Astronomy
    Type: GSFC-E-DAA-TN7227 , The Astorhysical Journal; 762; 1; 48
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    NASA TECHNICAL REPORTS
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