TU Ophiuchi: Mira variable — Not dwarf nova

High-speed photometry, spectroscopy, and visual observations of TU Oph show it to be a Mira variable, not a dwarf nova as originally classified or a UV Cet star as tentatively classified.     

Strained co-ordinate methods in rotating stars

It was shown in a previous paper, Smith (1975), that the determination of the structure of rotating polytropes by expansion in the small rotational parameter constitutes asingular perturbation problem as arises also, for example, in large Reynolds' number approximations in fluid dynamics. The technique used by him — the method of matched asymptotic expansions — is, in fact, just an extension of the Prandtl boundary layer theory familiar in this latter context. In this paper — the first of two — we introduce an alternative procedure: the method of strained co-ordinates; and for comparison purposes again consider rotating polytropes. In Paper II we extend this approach to differentially rotating stars and present an illustrative example.     

THE LADDER CREEK,HORACE, AND TRIBUNE METEORITES (GREELEY COUNTY,KANSAS)

The Ladder Creek, Horace No. 1, Horace No. 2, and Tribune meteorites were found within a comparatively small area of Greeley County, Kansas, between 1937 and 1958. Microscopic examination and analyses of the principal minerals show that Ladder Creek, Horace No. 2, and Tribune are essentially identical in composition and structure; it seems reasonable to conclude they are fragments of a single meteorite, a hypersthene chondrite. Horace No. 1 is essentially different, being a bronzite chondrite, and is evidently a distinct fall. The name Ladder Creek should be used for specimens previously called Horace No. 2 and Tribune, and the name Horace should be used for specimens previously called Horace No. 1.     

On the general properties of the secondaries of cataclysmic variable stars

The mass-radius, mass-orbital period, spectral type-orbital period and absolute magnitude-orbital period relationships for the secondary star components of cataclysmic variable (CV) binary stars are discussed. By comparing these with those expected for systems containing Roche lobe-filling main sequence stars, using empirical data for low-mass main sequence stars, it is shown thatas a group the CV secondaries do not differ significantly from main sequence stars.     

Towards identifying sources of subsurface flow: A comparison of components identified by a physically based runoff model and those determined by chemical mixing techniques

A physically-based semidistributed model, TOPMODEL, is applied to a 340 hectare spruce forested catchment in mid-Wales. the model is calibrated to runoff and the subsurface flow is divided into components of flow identified by depth of origin. in addition, chemical mixing techniques are used to provide a hydrograph separation between acidic soil waters and well buffered deep waters. the short-term variations in the components of flow identified by these two approaches compare well.     

Nickel, Copper, Zinc and Cadmium Cycling with Manganese in Lake Vanda (Wright Valley, Antarctica)

Lake Vanda is a closed-basin, permanently ice-covered lake located in the Wright Valley of Antarctica. The lakes more important geochemical features include the fact that it is fed by a single glacial melt water stream for only 6–8weeks out of the year; that it has remained stratified for more than a millennium; and that, like other lakes in the region, it is remote from anthropogenic influence. These, together with the fact that it is among the least biologically productive lakes in the world, make it an ideal system for examining the transport, cycling and fate of trace metals in the aquatic environment. Like others before us, we view this lake as a natural geochemical laboratory, a flask in the desert. This paper presents the first set of closely spaced, vertical, profiles for dissolved and particulate Mn, Fe, Ni, Cu, Zn and Cd in the water column. Despite the absence of an outflow, metals in the fresh upper waters of the lake have extremely low concentrations, in the pico-molar to nano-molar range, and are partitioned largely into dissolved rather than particulate phases. Efficient metal scavenging by particles from these oxygen-rich waters is indicated. Significant increases in metal concentrations begin to appear at depth, between 57 and 60m, and these increases coincide with the onset of manganese oxide dissolution in oxic, but lower pH waters. Vertical profiles suggest that the entire suite of trace metals (Ni, Cu, Zn, and Cd) is being released from manganese oxide carrier phases. Thermodynamic analysis indicates that Mn3O4 (i.e., the mineral hausmannite) may be important in metal sequestration and recycling in the deeper waters of Lake Vanda. Manganese-reducing organisms reported by Bratina etal. (1998) are active in the zone of metal release and these could also contribute to the observed cycling.     

Determination of the properties of Mercury's magnetic field by the MESSENGER mission

The MESSENGER mission to Mercury, to be launched in 2004, will provide an opportunity to characterize Mercury's internal magnetic field during an orbital phase lasting one Earth year. To test the ability to determine the planetary dipole and higher-order moments from measurements by the spacecraft's fluxgate magnetometer, we simulate the observations along the spacecraft trajectory and recover the internal field characteristics from the simulated observations. The magnetic field inside Mercury's magnetosphere is assumed to consist of an intrinsic multipole component and an external contribution due to magnetospheric current systems described by a modified Tsyganenko 96 model. Under the axis-centered-dipole approximation without correction for the external field the moment strength is overestimated by ∼4% for a simulated dipole moment of , and the error depends strongly on the magnitude of the simulated moment, rising as the moment decreases. Correcting for the external field contributions can reduce the error in the dipole term to a lower limit of ∼1-2% without a solar wind monitor. Dipole and quadrupole terms, although highly correlated, are then distinguishable at the level equivalent to an error in the position of an offset dipole of a few tens of kilometers. Knowledge of the external magnetic field is therefore the primary limiting factor in extracting reliable knowledge of the structure of Mercury's magnetic field from the MESSENGER observations.