47,721 research outputs found
Validation of a Temperate Fourth Planet in the K2-133 Multi-planet System
We present follow-up observations of the K2-133 multi-planet system.
Previously, we announced that K2-133 contained three super-Earths orbiting an
M1.5V host star - with tentative evidence of a fourth outer-planet orbiting at
the edge of the temperate zone. Here we report on the validation of the
presence of the fourth planet, determining a radius of
R. The four planets span the radius gap of the exoplanet population,
meaning further follow-up would be worthwhile to obtain masses and test
theories of the origin of the gap. In particular, the trend of increasing
planetary radius with decreasing incident flux in the K2-133 system supports
the claim that the gap is caused by photo-evaporation of exoplanet atmospheres.
Finally, we note that K2-133 e orbits on the edge of the stars temperate zone,
and that our radius measurement allows for the possibility that this is a rocky
world. Additional mass measurements are required to confirm or refute this
scenario.Comment: Accepted for publication in MNRA
Three small transiting planets around the M dwarf host star LP 358-499
We report on the detection of three transiting small planets around the
low-mass star LP 358-499 (K2-133), using photometric data from the Kepler-K2
mission. Using multiband photometry, we determine the host star to be an early
M dwarf with an age likely older than a Gigayear. The three detected planets
K2-133 b, c, and d have orbital periods of ca. 3, 4.9 and 11 days and transit
depths of ca. 700, 1000 and 2000 ppm, respectively. We also report a planetary
candidate in the system (EPIC 247887989.01) with a period of 26.6 days and a
depth of ca. 1000 ppm, which may be at the inner edge of the stellar habitable
zone, depending on the specific host star properties. Using the transit
parameters and the stellar properties, we estimate that the innermost planet
may be rocky. The system is suited for follow-up observations to measure
planetary masses and JWST transmission spectra of planetary atmospheres.Comment: Accepted for publication in MNRAS Letters. Replaced previous arXiv
version with final submitted versio
The extended hypergeometric class of L\'evy processes
With a view to computing fluctuation identities related to stable processes,
we review and extend the class of hypergeometric L\'evy processes explored in
Kuznetsov and Pardo (arXiv:1012.0817). We give the Wiener-Hopf factorisation of
a process in the extended class, and characterise its exponential functional.
Finally, we give three concrete examples arising from transformations of stable
processes.Comment: 22 page
Executive computer program for linking independent computer programs: ODINEX
Program controls sequence of execution of network of program elements and maintains data base of common information which forms communication link among them. Approach is applicable to any multiple-program task
Nitrogen transfer between clover and wheat in an intercropping experiment
A novel approach to the problem of improving nitrogen supply in organic farming is to use intercropping of cereals with a legume to provide nitrogen transfer within a season and/or to following crops. The affects of intercropping were studied in a column experiment using mixtures of winter wheat (Triticum aestivum cv. Claire), with white clover (w.c.) (Trifolium repens cv. Barblanca) and with red clover (r.c.) (Trifolium pratense cv. Britta). The effects of cutting and removal above ground clover material with and without additional soil disturbance were compared to leaving clover plants in situ and intercropped with wheat in a split root design. Wheat and clover plants, as monocultures, were used for the controls. 15N ammonium nitrate solution was applied. The wheat seeds were sown into the column without nitrogen. We found that the cutting treatment produced the highest yield of wheat. Available ammonium-N in the soil was greatest in the clover control treatment for the column with only red clover roots and in the cutting+soil disturbance treatment for the column with only white clover roots. Available nitrate-N was greatest in the soil disturbance treatment in the column with clover and wheat roots for both red and white clover. The cutting treatment produced the highest yield of wheat
Electric arc apparatus Patent
Electric arc heater with supersonic nozzle and fixed arc length for use in high temperature wind tunnel
Improving supply and phosphorous use efficiency in organic farming systems
Phosphorus (P) is an essential plant nutrient that needs to be managed carefully in organic systems so that crop yield and quality remain sustainable without contributing to environmental damage, particularly that associated with eutrophication. Under organic regulations, minimally processed rock phosphate (PR) can be used to amend low P fertility soils, although the solubility is extremely low at optimum soil pH for most crop growth (pH 6.5). This paper describes a project (PLINK) which aims to develop methods of improving P efficiency on organic farms, although the same approaches may also be applicable on conventional and low-input farms. The methodologies that the project is developing include the fermentation and composting of crop waste material with PR in order to solubilise P and make it more available to the crop. Some initial results are described here. In addition, the project will investigate the alteration of the rotation to include crops or varieties with high P uptake efficiency, or roots that possess acidifying properties which improve P availability for following crops
A new Viola (Violaceae) from the Argentinian Andes
Viola beati, a hitherto unknown species of V. sect. Andinium (Violaceae) is described and illustrated. It is an inconspicuous, diminutive, perennial forb currently known from only one locality in NW Argentina. We draw attention to its morphology, ecology, rarity and endemism. The differences between V. beati and its apparently only close relative, V. singularis J. M. Watson & A. R. Flores, are defined
Indicator systems - resource use in organic systems
A balanced use of resources within organic farming systems is required to maintain sustainable systems. Hence, it is essential to have tools that can assess the use of resources within the farming system and their impact on the environment. The range of tools that have been developed include those assessing local farm-scale issues together with those that assess impacts at the global scale. At the global scale assessments are usually made on the basis of a unit of product whereas at the local scale assessments can also be made on an area basis. In addition, the tools also assess a variety of issues, e.g. biodiversity, pollution potential, energy and water use. The level of detail required for the different assessment tools differs substantially; nevertheless it is essential that the indicator systems developed are based on sound knowledge, are acceptable to the farmers and can guide their future actions
Effect of Reynolds number on stability characteristics of a cruciform wing-body
An experimental investigation was conducted to determine the effect of Reynolds number on the stability characteristics of a body with cruciform wings at large angles of attack. Pressure distributions and force and moment data (axial force not measured) are presented for Mach 1.60 and 2.70, Reynolds numbers based on body diameter from approximately 130,000 to 2,800,000, and angles of attack from 0 deg to 50 deg. In general, the data show only small effects of Reynolds number throughout the range of test condition. Also discussed are force balance and pressure data that suggest a direct relationship between wind choking and the onset of a nonlinear stability variaton with angle of attack
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