288 research outputs found

    Potato Production near Glyphosate-resistant Crops — Injury Potential

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    The herbicide glyphosate is used in many countries because of low cost and effective weed control, but low levels of glyphosate on potato can reduce yield, marketability, and seed quality. Glyphosate is a phloem-mobile herbicide that can translocate to tubers, causing malformations that reduce the quality of current-season production. Potato plants are most susceptible to glyphosate at the hooking or tuber initiation stage. Tubers exposed at these stages often will become malformed and yield loss can occur. Seed production can be affected because glyphosate degradation is slow and it translocates to tubers. Seed potato exposed to glyphosate can store glyphosate residues until they are planted the next season. Tubers planted with glyphosate residues will have an erratic and slow emergence pattern, bending and twisting of leaves, multiple shoots from eyes, “candelabra” or “cauliflower” formation of shoots, or completely inhibited shoot growth, depending on the rate and cultivar. Glyphosate-affected seed tubers produce less tuber set and tubers with reduced weight. Tubers suspected to have glyphosate injury should be tested at a reputable laboratory to confirm glyphosate residues are present. Good management practices can help prevent potato from being exposed to glyphosate

    Alpha Enhancement and the Metallicity Distribution Function of Plaut's Window

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    We present Fe, Si, and Ca abundances for 61 giants in Plaut's Window (l=-1,b=-8.5) and Fe abundances for an additional 31 giants in a second, nearby field (l=0,b=-8) derived from high resolution (R~25,000) spectra obtained with the Blanco 4m telescope and Hydra multifiber spectrograph. The median metallicity of red giant branch (RGB) stars in the Plaut field is ~0.4 dex lower than those in Baade's Window, and confirms the presence of an iron abundance gradient along the bulge minor axis. The full metallicity range of our (biased) RGB sample spans -1.5<[Fe/H]<+0.3, which is similar to that found in other bulge fields. We also derive a photometric metallicity distribution function for RGB stars in the (l=-1,b=-8.5) field and find very good agreement with the spectroscopic metallicity distribution. The radial velocity and dispersion data for the bulge RGB stars are in agreement with previous results of the BRAVA survey, and we find evidence for a decreasing velocity dispersion with increasing [Fe/H]. The [alpha/Fe] enhancement in Plaut field stars is nearly identical to that observed in Baade's window, and suggests that an [alpha/Fe] gradient does not exist between b=-4 and -8. Additionally, a subset of our sample (23 stars) appear to be foreground red clump stars that are very metal--rich, exhibit small metallicity and radial velocity dispersions, and are enhanced in alpha elements. While these stars likely belong to the Galactic inner disk population, they exhibit [alpha/Fe] ratios that are enhanced above the thin and thick disk.Comment: Accepted for publication in ApJ. 38 pages, 11 figures, and 2 tables. Requests for higher resolution figures and electronic versions of tables 1 and/or 2 in advance of publication may be sent to cijohnson[at]astro.ucla.ed

    Retired A Stars and Their Companions VI. A Pair of Interacting Exoplanet Pairs Around the Subgiants 24 Sextanis and HD200964

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    We report radial velocity measurements of the G-type subgiants 24 Sextanis (=HD90043) and HD200964. Both are massive, evolved stars that exhibit periodic variations due to the presence of a pair of Jovian planets. Photometric monitoring with the T12 0.80m APT at Fairborn Observatory demonstrates both stars to be constant in brightness to <= 0.002 mag, thus strengthening the planetary interpretation of the radial velocity variations. 24 Sex b,c have orbital periods of 453.8 days and 883~days, corresponding to semimajor axes 1.333 AU and 2.08 AU, and minimum masses (Msini) 1.99 Mjup and 0.86 Mjup, assuming a stellar mass 1.54 Msun. HD200964 b,c have orbital periods of 613.8 days and 825 days, corresponding to semimajor axes 1.601 AU and 1.95 AU, and minimum masses 1.85 Mjup and 0.90 Mjup, assuming M* = 1.44 Msun. We also carry out dynamical simulations to properly account for gravitational interactions between the planets. Most, if not all, of the dynamically stable solutions include crossing orbits, suggesting that each system is locked in a mean motion resonance that prevents close encounters and provides long-term stability. The planets in the 24 Sex system likely have a period ratio near 2:1, while the HD200964 system is even more tightly packed with a period ratio close to 4:3. However, we caution that further radial velocity observations and more detailed dynamical modelling will be required to provide definitive and unique orbital solutions for both cases, and to determine whether the two systems are truly resonant.Comment: AJ accepte

    M2K: II. A Triple-Planet System Orbiting HIP 57274

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    Doppler observations from Keck Observatory have revealed a triple planet system orbiting the nearby mid-type K dwarf, HIP 57274. The inner planet, HIP 57274b, is a super-Earth with \msini\ = 11.6 \mearth (0.036 \mjup), an orbital period of 8.135 ±\pm 0.004 d, and slightly eccentric orbit e=0.19±0.1e=0.19 \pm 0.1. We calculate a transit probability of 6.5% for the inner planet. The second planet has \msini\ = 0.4 \mjup\ with an orbital period of 32.0 ±0.02\pm 0.02 d in a nearly circular orbit, and e=0.05±0.03e = 0.05 \pm 0.03. The third planet has \msini\ = 0.53 \mjup\ with an orbital period of 432 ±8\pm 8 d (1.18 years) and an eccentricity e=0.23±0.03e = 0.23 \pm 0.03. This discovery adds to the number of super Earth mass planets with \msini < 12 \mearth\ that have been detected with Doppler surveys. We find that 56 ±18\pm 18% super-Earths are members of multi-planet systems. This is certainly a lower limit because of observational detectability limits, yet significantly higher than the fraction of Jupiter mass exoplanets, 20±820 \pm 8%, that are members of Doppler-detected, multi-planet systems.Comment: 11 figures, submitte to ApJ on Sept 10, 201

    The First Extrasolar Planet Discovered with a New Generation High Throughput Doppler Instrument

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    We report the detection of the first extrasolar planet, ET-1 (HD 102195b), using the Exoplanet Tracker (ET), a new generation Doppler instrument. The planet orbits HD 102195, a young star with solar metallicity that may be part of the local association. The planet imparts radial velocity variability to the star with a semiamplitude of 63.4±2.063.4\pm2.0 m s1^{-1} and a period of 4.11 days. The planetary minimum mass (msinim \sin i) is 0.488±0.0150.488\pm0.015 MJM_J.Comment: 42 pages, 11 figures and 5 tables, Accepted for publication in Ap

    Discovery and Follow-up Observations of the Young Type Ia Supernova 2016coj

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    The Type~Ia supernova (SN~Ia) 2016coj in NGC 4125 (redshift z=0.004523z=0.004523) was discovered by the Lick Observatory Supernova Search 4.9 days after the fitted first-light time (FFLT; 11.1 days before BB-band maximum). Our first detection (pre-discovery) is merely 0.6±0.50.6\pm0.5 day after the FFLT, making SN 2016coj one of the earliest known detections of a SN Ia. A spectrum was taken only 3.7 hr after discovery (5.0 days after the FFLT) and classified as a normal SN Ia. We performed high-quality photometry, low- and high-resolution spectroscopy, and spectropolarimetry, finding that SN 2016coj is a spectroscopically normal SN Ia, but with a high velocity of \ion{Si}{2} λ\lambda6355 (12,600\sim 12,600\,\kms\ around peak brightness). The \ion{Si}{2} λ\lambda6355 velocity evolution can be well fit by a broken-power-law function for up to a month after the FFLT. SN 2016coj has a normal peak luminosity (MB18.9±0.2M_B \approx -18.9 \pm 0.2 mag), and it reaches a BB-band maximum \about16.0~d after the FFLT. We estimate there to be low host-galaxy extinction based on the absence of Na~I~D absorption lines in our low- and high-resolution spectra. The spectropolarimetric data exhibit weak polarization in the continuum, but the \ion{Si}{2} line polarization is quite strong (0.9%±0.1%\sim 0.9\% \pm 0.1\%) at peak brightness.Comment: Submitte
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