An analysis of the shapes of interstellar extinction curves. VII Milky Way spectrophotometric optical-through-ultraviolet extinction and its R-dependence

We produce a set of 72 NIR-through-UV extinction curves by combining new Hubble Space Telescope/STIS optical spectrophotometry with existing International Ultraviolet Explorer spectrophotometry (yielding gapless coverage from 1150 to 10000 ?) and NIR photometry. These curves are used to determine a new, internally consistent NIR-through-UV Milky Way mean curve and to characterize how the shapes of the extinction curves depend on R(V). We emphasize that while this dependence captures much of the curve variability, considerable variation remains that is independent of R(V). We use the optical spectrophotometry to verify the presence of structure at intermediate wavelength scales in the curves. The fact that the optical-through-UV portions of the curves are sampled at relatively high resolution makes them very useful for determining how extinction affects different broadband systems, and we provide several examples. Finally, we compare our results to previous investigations

Review of the African genera Arantia Stål and Goetia Karsch (Orthoptera. Tettigoniidae: Phaneropterinae).

The genus Arantia is reviewed, the distribution and distinguishing characters given. The three species of Goetia are assigned as subgenus to Arantia. Arantia gestri Griffini is transferred to this new subgenus and synonymized with G. dimidiata Bolívar. Other species synonymized are: A. accrana Karsch with A. rectifolia Brunner von Wattenwyl; A. gabunensis Brunner von Wattenwyl with A. regina Karsch; A. mammisignum Karsch and A. tigrina Bolívar with A. excelsior Karsch; A. ugandana Rehn is synonymized with A. fasciata (Walker). 6 species from Tropical Africa are newly described: A. (Arantia) quinquemaculata n. sp., A. (Arantia) ivoriana n. sp., A. (Euarantia) tanzanica n. sp., A. (Euarantia) tibiaspinosa n. sp., A. (Euarantia) bispinosa n. sp. and A. (Euarantia) griffinii n. sp. A key to the subgenera and species of Arantia is provided. The tribe Arantiini is synonymized with Holochlorini

Semi-Teleparallel Theories of Gravitation

A class of theories of gravitation that naturally incorporates preferred frames of reference is presented. The underlying space-time geometry consists of a partial parallelization of space-time and has properties of Riemann-Cartan as well as teleparallel geometry. Within this geometry, the kinematic quantities of preferred frames are associated with torsion fields. Using a variational method, it is shown in which way action functionals for this geometry can be constructed. For a special action the field equations are derived and the coupling to spinor fields is discussed.Comment: 14 pages, LaTe

Detection of a Hot Binary Companion of η\eta Carinae

We report the detection of a hot companion of $\eta$ Carinae using high resolution spectra (905 - 1180 \AA) obtained with the Far Ultraviolet Spectroscopic Explorer (\fuse) satellite. Observations were obtained at two epochs of the 2024-day orbit: 2003 June during ingress to the 2003.5 X-ray eclipse and 2004 April several months after egress. These data show that essentially all the far-UV flux from \etacar shortward of \lya disappeared at least two days before the start of the X-ray eclipse (2003 June 29), implying that the hot companion, \etaB, was also eclipsed by the dense wind or extended atmosphere of \etaA. Analysis of the far-UV spectrum shows that \etaB is a luminous hot star. The \nii \wll1084-1086 emission feature suggests that it may be nitrogen-rich. The observed far-UV flux levels and spectral features, combined with the timing of their disappearance, is consistent with \etacar\ being a massive binary system

New Ultraviolet Extinction Curves for Interstellar Dust in M31

New low-resolution UV spectra of a sample of reddened OB stars in M31 were obtained with HST/STIS to study the wavelength dependence of interstellar extinction and the nature of the underlying dust grain populations. Extinction curves were constructed for four reddened sightlines in M31 paired with closely matching stellar atmosphere models. The new curves have a much higher S/N than previous studies. Direct measurements of N(H I) were made using the Ly$\alpha$ absorption lines enabling gas-to-dust ratios to be calculated. The sightlines have a range in galactocentric distance of 5 to 14 kpc and represent dust from regions of different metallicities and gas-to-dust ratios. The metallicities sampled range from Solar to 1.5 Solar. The measured curves show similarity to those seen in the Milky Way and the Large Magellanic Cloud. The Maximum Entropy Method was used to investigate the dust composition and size distribution for the sightlines observed in this program finding that the extinction curves can be produced with the available carbon and silicon abundances if the metallicity is super-Solar.Comment: ApJ, in press, 9 pages, 5 figure

Sensory Aids Research

Contains a report on a research project