A catalogue of RR Lyrae stars from the Northern Sky Variability Survey

A search for RR Lyrae stars has been conducted in the publicly available data of the Northern Sky Variability Survey. Candidates have been selected by the statistical properties of their variation; the standard deviation, skewness and kurtosis with appropriate limits determined from a sample 314 known RRab and RRc stars listed in the General Catalogue of Variable Stars. From the period analysis and light-curve shape of over 3000 candidates 785 RR Lyrae have been identified of which 188 are previously unknown. The light curves were examined for the Blazhko effect and several new stars showing this were found. Six double-mode RR Lyrae stars were also found of which two are new discoveries. Some previously known variables have been reclassified as RR Lyrae stars and similarly some RR Lyrae stars have been found to be other types of variable, or not variable at all.     

Pre-industrial-potential and Last Glacial Maximum global vegetation simulated with a coupled climate-biosphere model: diagnosis of bioclimatic relationships

The global climate–vegetation model HadSM3_TRIFFID has been used to estimate the equilibrium states of climate and vegetation with pre-industrial and last glacial boundary conditions. The present study focuses on the evaluation of the terrestrial biosphere component (TRIFFID) and its response to changes in climate and CO₂ concentration. We also show how, by means of a diagnosis of the distribution of plant functional types according to climate parameters (soil temperature, winter temperature, growing-degree days, precipitation), it is possible to get better insights into the strengths and weaknesses of the biosphere model by reference to field knowledge of ecosystems.The model exhibits profound changes between the vegetation distribution at the Last Glacial Maximum and today that are generally consistent with palaeoclimate data, such as the disappearance of the Siberian boreal forest (taiga), an increase in shrub cover in Europe and an increase of the subtropical desert area. The effective equatorial and sub-tropical tree area is reduced by 18%. There is also an increase in cover of wooded species in North-Western Africa and in Mexico. The analysis of bioclimatic relationships turns out to be an efficient method to infer the contributions of different climatic factors to vegetation changes, both at high latitudes, where the position of the boreal treeline appears in this model to be more directly constrained by the water stress than by summer temperature, and in semi-humid areas where the contributions of temperature and precipitation changes may partly compensate each other. Our study also confirms the major contribution of the decrease in CO₂ to environmental changes and carbon storage through its selective impact on gross primary productivity of C3 and C4 plants and a reduction by 25% of water-use efficiency. Specifically, the reduction in CO₂ concentration increases the amount of precipitation necessary to sustain at least 20% of grass fraction by 50 mm/year; the corresponding threshold for trees is increased by about 150 mm/year. As a consequence, a reduction in CO₂ concentration considerably widens the climatic range where grasses and shrubs dominate.     

Deep Impact photometry of Comet 9P/Tempel 1

The photometric properties of the nucleus of Comet 9P/Tempel 1 are studied from the disk-resolved color images obtained by Deep Impact (DI). Comet Tempel 1 has typical photometric properties for comets and dark asteroids. The disk-integrated spectrum of the nucleus of Tempel 1 between 309 and 950 nm is linear without any features at the spectral resolution of the filtered images. At V-band, the red slope of the nucleus is 12.5±1% per 100 nm at 63° phase angle, translating to B-V=0.84±0.01, V-R=0.50±0.01, and R-I=0.49±0.02. No phase reddening is confirmed. The phase function of the nucleus of Tempel 1 is constructed from DI images and earlier ground-based observations found from the literature. The phase coefficient is determined to be β=0.046±0.007 mag/deg between 4° and 117° phase angle. Hapke's theoretical scattering model was used to model the photometric properties of this comet. Assuming a single Henyey-Greenstein function for the single-particle phase function, the asymmetry factor of Tempel 1 was fitted to be g=−0.49±0.02, and the corresponding single-scattering albedo (SSA) was modeled to be 0.039±0.005 at 550 nm wavelength. The SSA spectrum shows a similar linear slope to that of the disk-integrated spectrum. The roughness parameter is found to be 16°±8°, and independent of wavelength. The Minnaert k parameter is modeled to be 0.680±0.014. The photometric variations on Tempel 1 are relatively small compared to other comets and asteroids, with a ∼20% full width at half maximum of albedo variation histogram, and ∼3% for color. Roughness variations are evident in one small area, with a roughness parameter about twice the average and appearing to correlate with the complex morphological texture seen in high-resolution images.     

Hydrologic characteristics of Appalachian loose‐dumped spoil in the Cumberland Plateau of eastern Kentucky

Heavily compacted lands, typical of traditional surface mine reclamation techniques, have been shown to hinder tree growth, increase levels of flooding, and produce suboptimal water quality. Utilizing loose‐dumped spoil, in accordance with the Forestry Reclamation Approach (FRA), has demonstrated success with regards to promoting tree growth and survival; however, additional information is needed to assess the potential of FRA to ameliorate other environmental concerns related to water quantity. To better understand the hydrologic characteristics of loose‐dumped spoil, key hydrograph parameters (discharge volume, peak discharge, discharge duration, lag time, and response time) were monitored for three common spoil types: (1) predominately brown weathered sandstone, (2) predominately gray weathered sandstone, and (3) a mixture of both sandstones and shale. Although spoil types were found to differ hydrologically, these differences were relatively minor. Measured discharge volumes were low (averaging 12% of rainfall for all events and treatments), peak discharge rates were small (between 2·5 × 10^?5 and 3 × 10^?3 m³/s), and the duration of discharge was long (6 days on average). From a hydrologic perspective, the results of this study indicate that mine spoils need not be segregated for reclamation as long as the spoil is placed in accordance with the loose‐dumped techniques as outlined in the FRA. Copyright © 2009 John Wiley & Sons, Ltd.     

A simple expression for vertical convective fluxes in planetary atmospheres

We explore the vertical convective flux F_c in a radiative-convective grey atmosphere. An expression of the form F_c=F_sτ_o/(C+Dτ_o) appears useful, where F_s is the shortwave flux absorbed at the base of an atmosphere with longwave optical depth τ_o and C and D are constants. We find excellent agreement with an idealized grey radiative-convective model with no shortwave absorption for D=1 and C=1∼2 depending on the surface-atmosphere temperature contrast and on the imposed critical lapse rate. Where shortwave absorption is correlated with longwave opacity, as in the atmospheres of Earth and Titan, C=2, D=2 provides an excellent fit, validated against the present terrestrial situation and the results of a nongrey model of Titan's strongly antigreenhouse atmosphere under a wide range of conditions. The expression may be useful for studying the energetics of planetary climates through time where there is insufficient data to constrain more elaborate models.     

Chemical enrichment by Wolf–Rayet stars: non-solar metallicities

Following on from our recent Paper I, we present theoretical models of Wolf–Rayet (WR) stars for non-solar metallicities from   Z = 0.03  to 0.0001 by mass fraction with different mass-loss rate assumptions. We find that some single WR stars may still form even at the lowest metallicities, but whether this occurs or not depends critically on the upper cut-off point of the initial mass function used. As at solar metallicity, a population of binaries is required to fully reproduce WR star observations. For most scenarios, these binaries dominate the low-metallicity WR population but probably not the enrichment. We find comparable carbon enrichment from single WR stars to that from asymptotic giant branch stars at all metallicities for which data are available, but which of them is the dominant source of carbon depends strongly on the set of asymptotic giant branch yields adopted and the assumed initial mass function. We find an increase in carbon enrichment with increasing metallicity but a decrease in oxygen enrichment, as confirmed by observation.     

Organic compounds in the Murchison and Allende carbonaceous chondrites studied by photoionization mass spectrometry

Abstract— Organic compounds in the Murchison (C2M) and Allende (CV3) carbonaceous chondrites were analyzed by photoionization time-of-flight mass spectrometry; thermal (25–850 °C) and stimulated (7 keV Ar⁺) desorption were combined with either nonresonant single-photon ionization using 118 nm light or resonantly enhanced multiphoton ionization (selective for aromatic compounds) using 266 nm light. Samples weighing only 1–10 mg were sufficient for sensitive quantitative analysis of aromatic compounds using thermal desorption. The detection limits for phenanthrene and pyrene using 118 nm light were determined to be 0.8 and 1.4 picomoles, respectively, and the concentrations of these compounds (including their isomers anthracene and fluoranthene) in the Murchison meteorite were determined to be 9 and 12 μg/g, respectively, in good agreement with previously published values. Thermal-desorption (–75–500 °C) field-ionization mass spectra (activated foil-type ionizing source and magnetic sector mass analyzer) of 20–40 mg of the same meteorite material were obtained to verify that the 118 nm photoionization mass spectra were not affected by photofragmentation or photodecomposition and were representative of the organic material extracted by thermal desorption. Photoionization mass spectrometry is a useful technique for studying small quantities (< 1 nanomole) of organic matter in terrestrial and extraterrestrial samples. The present study aims to provide the background and analytical methods necessary for application to new and unsolved cosmochemical problems. Some potential applications are discussed.