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- Crossfield, Ian J. M., et al.
(author)
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197 CANDIDATES AND 104 VALIDATED PLANETS IN K2's FIRST FIVE FIELDS
- 2016
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In: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 226:1
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Journal article (peer-reviewed)abstract
- We present 197 planet candidates discovered using data from the first year of the NASA K2 mission (Campaigns 0-4), along with the results of an intensive program of photometric analyses, stellar spectroscopy, high-resolution imaging, and statistical validation. We distill these candidates into sets of 104 validated planets (57 in multi-planet systems), 30 false positives, and 63 remaining candidates. Our validated systems span a range of properties, with median values of R-P = 2.3 R-circle plus, P = 8.6 days, T-eff = 5300 K, and Kp = 12.7 mag. Stellar spectroscopy provides precise stellar and planetary parameters for most of these systems. We show that K2 has increased by 30% the number of small planets known to orbit moderately bright stars (1-4 R-circle plus, Kp = 9-13. mag). Of particular interest are 76 planets smaller than 2 R-circle plus, 15 orbiting stars brighter than Kp = 11.5. mag, 5 receiving Earth-like irradiation levels, and several multi-planet systems-including 4 planets orbiting the M dwarf K2-72 near mean-motion resonances. By quantifying the likelihood that each candidate is a planet we demonstrate that our candidate sample has an overall false positive rate of 15%-30%, with rates substantially lower for small candidates (<2 R-circle plus) and larger for candidates with radii >8 R-circle plus and/or with P < 3 days. Extrapolation of the current planetary yield suggests that K2 will discover between 500 and 1000 planets in its planned four-year mission, assuming sufficient follow-up resources are available. Efficient observing and analysis, together with an organized and coherent follow-up strategy, are essential for maximizing the efficacy of planet-validation efforts for K2, TESS, and future large-scale surveys.
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| 2. |
- Gilbert, F., et al.
(author)
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Redox oscillation and benthic nitrogen mineralization within burrowed sediments: An experimental simulation at low frequency
- 2016
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In: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 482, s. 75-84
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Journal article (peer-reviewed)abstract
- Possible effects of sediment ventilation by benthic organisms on the nitrogen cycle were investigated using an experimental setup that mimicked stable or relatively low frequency oscillating redox conditions potentially found in bioturbated deposits. Three different conditions inside burrowed sediments were simulated using 2 mm thick sediment layers: 1) continuously oxic sediment exposed to oxygenated overlying bottom water (e.g., burrow walls, surface sediment), 2) continuously anoxic sediment out of reach from either O-2 or NO3- diffusion and 3) the lining/boundary of burrow structures or sediment pockets (e.g., excavated during feeding) subject to intermittent irrigation and redox fluctuations over several day timescales. Results demonstrated that intermittent redox fluctuations allowed sustained denitrification and episodic nitrification, whereas significant denitrification and both nitrification and denitrification were absent after similar to 5-10 days from continuously oxidized and anoxic zones respectively. Intermittent redox oscillations enhance metabolic diversity, magnify loss of dissolved inorganic N to solution, and permit sustained coupling between ammonification, nitrification, and denitrification despite lack of a stable stratified oxic-anoxic redox structure. Even relatively low frequency redox oscillations induce greater N loss compared to sediment that is continuously exposed to oxic and anoxic conditions.
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