Thermal infrared observations of Mars (7.5-12.8 microns) during the 1990 opposition

Thirteen spectra of Mars, in the 7.5 to 12.8 micron wavelength were obtained on 7 Dec. 1990 from the Infrared Telescope Facility (IRTF). For these observations, a grating with an ultimate resolving power of 120 to 250 was used and wavelengths were calibrated for each grating setting by comparison with the absorption spectrum of polystyrene measured prior to each set of observations. By sampling the Nyquist limit at the shortest wavelengths, an effective resolving power of about 120 over the entire wavelength range was achieved. A total of four grating settings were required to cover the entire wavelength region. A typical observing sequence consisted of: (1) positioning the grating in one of the intervals; (2) calibrating the wavelength of positions; and (3) obtaining spectra for a number of spots on Mars. Several observations of the nearby stellar standard star, alpha Tauri, were also acquired throughout the night. Each Mars spectrum represents an average of 4 to 6 measurements of the individual Mars spots. As a result of this observing sequence, the viewing geometry for a given location or spot on Mars does not change, but the actual location of the spot on Mars's surface varies somewhat between the different grating settings. Other aspects of the study are presented

Can differences in the nickel abundance in Chandrasekhar mass models explain the relation between brightness and decline rate of normal Type Ia Supernovae?

The use of Type Ia supernovae as distance indicators relies on the determination of their brightness. This is not constant, but it can be calibrated using an observed relation between the brightness and the properties of the optical light curve (decline rate, width, shape), which indicates that brighter SNe have broader, slower light curves. However, the physical basis for this relation is not yet fully understood. Among possible causes are different masses of the progenitor white dwarfs or different opacities in Chandrasekhar-mass explosions. We parametrise the Chandrasekhar-mass models presented by Iwamoto et al (1999), which synthesize different amounts of Ni, and compute bolometric light curves and spectra at various epochs. Since opacity in SNe Ia is due mostly to spectral lines, it should depend on the mass of Fe-peak elements synthesized in the explosion, and on the temperature in the ejecta. Bolometric light curves computed using these prescriptions for the optical opacity reproduce the relation between brightness and decline rate. Furthermore, when spectra are calculated, the change in colour between maximum and two weeks later allows the observed relation between M_B(Max) and Dm_{15}(B) to be reproduced quite nicely. Spectra computed at various epochs compare well with corresponding spectra of spectroscopically normal SNeIa selected to cover a similar range of Dm_{15}(B) values.Comment: 25 pages, including 6 figures. Accepted for publication in Ap

Genetic-Algorithm-based Light Curve Optimization Applied to Observations of the W UMa star BH Cas

I have developed a procedure utilizing a Genetic-Algorithm-based optimization scheme to fit the observed light curves of an eclipsing binary star with a model produced by the Wilson-Devinney code. The principal advantages of this approach are the global search capability and the objectivity of the final result. Although this method can be more efficient than some other comparably global search techniques, the computational requirements of the code are still considerable. I have applied this fitting procedure to my observations of the W UMa type eclipsing binary BH Cassiopeiae. An analysis of V-band CCD data obtained in 1994/95 from Steward Observatory and U- and B-band photoelectric data obtained in 1996 from McDonald Observatory provided three complete light curves to constrain the fit. In addition, radial velocity curves obtained in 1997 from McDonald Observatory provided a direct measurement of the system mass ratio to restrict the search. The results of the GA-based fit are in excellent agreement with the final orbital solution obtained with the standard differential corrections procedure in the Wilson-Devinney code.Comment: 9 pages, 2 figures, 2 tables, uses emulateapj.st

The effect of exogenous glucose infusion on early embryonic development in lactating dairy cows

peer-reviewedThe objective of this study was to examine the effect of intravenous infusion of glucose on early embryonic development in lactating dairy cows. Nonpregnant, lactating dairy cows (n = 12) were enrolled in the study (276 ± 17 d in milk). On d 7 after a synchronized estrus, cows were randomly assigned to receive an intravenous infusion of either 750 g/d of exogenous glucose (GLUC; 78 mL/h of 40% glucose wt/vol) or saline (CTRL; 78 mL/h of 0.9% saline solution). The infusion period lasted 7 d and cows were confined to metabolism stalls for the duration of the study. Coincident with the commencement of the infusion on d 7 after estrus, 15 in vitro-produced grade 1 blastocysts were transferred into the uterine horn ipsilateral to the corpus luteum. All animals were slaughtered on d 14 to recover conceptuses, uterine fluid, and endometrial tissue. Glucose infusion increased circulating glucose concentrations (4.70 ± 0.12 vs. 4.15 ± 0.12 mmol/L) but did not affect milk production or dry matter intake. Circulating β-hydroxybutyrate concentrations were decreased (0.51 ± 0.01 vs. 0.70 ± 0.01 mmol/L for GLUC vs. CTRL, respectively) but plasma fatty acids, progesterone, and insulin concentrations were unaffected by treatment. Treatment did not affect either uterine lumen fluid glucose concentration or the mRNA abundance of specific glucose transporters in the endometrium. Mean conceptus length, width, and area on d 14 were reduced in the GLUC treatment compared with the CTRL treatment. A greater proportion of embryos in the CTRL group had elongated to all length cut-off measurements between 11 and 20 mm (measured in 1-mm increments) compared with the GLUC treatment. In conclusion, infusion of glucose into lactating dairy cows from d 7 to d 14 post-estrus during the critical period of conceptus elongation had an adverse impact on early embryonic development

Abundance stratification in Type Ia Supernovae - II: The rapidly declining, spectroscopically normal SN 2004eo

The variation of properties of Type Ia supernovae, the thermonuclear explosions of Chandrasekhar-mass carbon-oxygen white dwarfs, is caused by different nucleosynthetic outcomes of these explosions, which can be traced from the distribution of abundances in the ejecta. The composition stratification of the spectroscopically normal but rapidly declining SN2004eo is studied performing spectrum synthesis of a time-series of spectra obtained before and after maximum, and of one nebular spectrum obtained about eight months later. Early-time spectra indicate that the outer ejecta are dominated by oxygen and silicon, and contain other intermediate-mass elements (IME), implying that the outer part of the star was subject only to partial burning. In the inner part, nuclear statistical equilibrium (NSE) material dominates, but the production of 56Ni was limited to ~0.43 \pm 0.05 Msun. An innermost zone containing ~0.25 Msun of stable Fe-group material is also present. The relatively small amount of NSE material synthesised by SN2004eo explains both the dimness and the rapidly evolving light curve of this SN.Comment: 12 pages, 7 figures. Accepted for publication in MNRA

Dryland Clovers: A Phytochemical Resource

Recent developments in the utilisation of phytoestrogens of red clover (Wuttke et al., 2002) have encouraged us to investigate a wider range of Trifolium species for metabolites which could provide new product opportunities. The phytochemistry of the agronomically-important Trifolium species white (Trifolium repens) and red (T. pratense) clovers has been investigated in some detail (Foo et al., 2000; Sivakumaran et al., 2004). However numerous other clover species have been neglected in agriculture due to agronomic issues or the fact they are annuals and require more intensive management. While some of these clover species have been studied for their genetic diversity (Marshall et al., 2002), investigations of the chemical composition of these specific species has not been reported

Three-dimensional distribution of ejecta in Supernova 1987A at 10 000 days

Due to its proximity, SN 1987A offers a unique opportunity to directly observe the geometry of a stellar explosion as it unfolds. Here we present spectral and imaging observations of SN 1987A obtained ~10,000 days after the explosion with HST/STIS and VLT/SINFONI at optical and near-infrared wavelengths. These observations allow us to produce the most detailed 3D map of H-alpha to date, the first 3D maps for [Ca II] \lambda \lambda 7292, 7324, [O I] \lambda \lambda 6300, 6364 and Mg II \lambda \lambda 9218, 9244, as well as new maps for [Si I]+[Fe II] 1.644 \mu m and He I 2.058 \mu m. A comparison with previous observations shows that the [Si I]+[Fe II] flux and morphology have not changed significantly during the past ten years, providing evidence that it is powered by 44Ti. The time-evolution of H-alpha shows that it is predominantly powered by X-rays from the ring, in agreement with previous findings. All lines that have sufficient signal show a similar large-scale 3D structure, with a north-south asymmetry that resembles a broken dipole. This structure correlates with early observations of asymmetries, showing that there is a global asymmetry that extends from the inner core to the outer envelope. On smaller scales, the two brightest lines, H-alpha and [Si I]+[Fe II] 1.644 \mu m, show substructures at the level of ~ 200 - 1000 km/s and clear differences in their 3D geometries. We discuss these results in the context of explosion models and the properties of dust in the ejecta.Comment: Accepted for publication in Ap

Hydrodynamic Simulations of Propagating Warps and Bending Waves In Accretion Discs

We present the results of a study of propagating warp or bending waves in accretion discs. Three dimensional hydrodynamic simulations were performed using SPH, and the results of these are compared with calculations based on the linear theory of warped discs. We consider primarily the physical regime in which the dimensionless viscosity parameter `alpha' < H/r, the disc aspect ratio, so that bending waves are expected to propagate. We also present calculations in which `alpha' > H/r, where the warps are expected to behave diffusively. Small amplitude perturbations are studied in both Keplerian and slightly non Keplerian discs, and we find that the SPH results can be reasonably well fitted by those of the linear theory. The main results of these calculations are: (1) the warp in Keplerian discs when `alpha' < H/r propagates with little dispersion and damps at a rate expected from estimates of the code viscosity, (2) warps evolve diffusively when `alpha' > H/r, (3) the non Keplerian discs exhibit a substantially more dispersive behaviour of the warps. Initially imposed higher amplitude nonlinear warping disturbances were studied in Keplerian discs. The results indicate that nonlinear warps can lead to the formation of shocks, and that the evolution of the warp becomes less wave-like and more diffusive in character. This work is relevant to the study of the warped accretion discs that may occur around Kerr black holes or in misaligned binary systems. The results indicate that SPH can accurately model the hydrodynamics of warped discs, even when using rather modest numbers of particles.Comment: 14 pages, 9 figures, to appear in MNRA

Models for the Type Ic Hypernova SN 2003lw associated with GRB 031203

The Gamma-Ray Burst 031203 at a redshift z=0.1055 revealed a highly reddened Type Ic Supernova, SN 2003lw, in its afterglow light. This is the third well established case of a link between a long-duration GRB and a type Ic SN. The SN light curve is obtained subtracting the galaxy contribution and is modelled together with two spectra at near-maximum epochs. A red VLT grism 150I spectrum of the SN near peak is used to extend the spectral coverage, and in particular to constrain the uncertain reddening, the most likely value for which is E_{G+H}(B-V) about 1.07 +/- 0.05. Accounting for reddening, SN 2003lw is about 0.3 mag brighter than the prototypical GRB-SN 1998bw. Light curve models yield a 56Ni mass of about 0.55 solar mass. The optimal explosion model is somewhat more massive (ejecta mass about 13 solar mass) and energetic (kinetic energy about 6 times 10^52 erg) than the model for SN 1998bw, implying a massive progenitor (40 - 50 solar mass). The mass at high velocity is not very large (1.4 solar mass above 30000 km/s, but only 0.1 solar mass above 60000 km/s), but is sufficient to cause the observed broad lines. The similarity of SNe 2003lw and 1998bw and the weakness of their related GRBs, GRB031203 and GRB980425, suggest that both GRBs may be normal events viewed slightly off-axis or a weaker but possibly more frequent type of GRB.Comment: 19 pages, 8 figures, accepted for publication in Ap