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A spectral analysis of the hydrogen-deficient star HD 144941.
Jeffery, C. S.; Harrison, P. M.
HD144941 is a B type hydrogen-deficient star. Previous analysis has suggested that its effective temperature and surface gravity are similar to the nitrogen rich H-deficient star V652 Her. However, its H/He ratio puts it between the classifications of an extreme and an intermediate helium star, and its low C and N abundances make it unique amongst…
Observations of Structures in the Inner Coma of Chiron with the HST Planetary Camera
Samarasinha, Nalin H.; Buie, Marc W.; Mueller, Beatrice E. A. +2 more
We have obtained a series of images of 2060 Chiron with the HST Planetary Camera on 3 nights near its minimum geocentric distance in 1993 (Delta = 8.342 AU). Extended structure was visible within a radial distance of 0.3'' from the nucleus. We interpret the structure to be the bound ballistic atmosphere and exopause boundary (at R_e~ 1800 km) hypo…
Dust in the Small Magellanic Cloud: Interstellar Polarization and Extinction
Magalhães, A. M.; Rodrigues, C. V.; Coyne, G. V. +1 more
The typical extinction curve for the Small Magellanic Cloud (SMC), in contrast to that for the Galaxy, has no bump at 2175 Å and a steeper rise into the far-ultraviolet. For the Galaxy, the interpretation of the extinction, and therefore the dust content of the interstellar medium, has been greatly assisted by measurements of the wavelength depend…
Atomic Sulfur in Cometary Comae Based on UV Spectra of the S ITriplet near 1814 Å
A'Hearn, Michael F.; Meier, Roland
We present a detailed study of the S I triplet emissions near 1814 Å in a variety of comets. Even in a moderately dense cometary coma the ground-state component (1807 Å) of the triplet turns out to be more or less optically deep. Therefore, any straightforward interpretation of the measured S I flux in terms of a gfactor and a column density is in…
SATI: a spectral airglow temperature imager
Rodrigo, R.; Wiens, R. H.; Moise, A. +6 more
An empirical understanding of planetary scale perturbations in the upper atmosphere is most effectively gained by the complementary use of both satellite and ground-based instrumentation. Limb observations from space provide vertical information and broad global coverage, while ground-based observations provide detailed system development in both …
GHRS Observations of Cool Low-Gravity Stars. III. Plasma Flows and Turbulence in the Outer Atmosphere of α Orionis (M2 Iab)
Robinson, Richard D.; Carpenter, Kenneth G.
We present the results of a Goddard High Resolution Spectrograph (GHRS) study of flow and turbulent velocities in the outer atmosphere of the M2 Iab supergiant α Ori. Ions with observed chromospheric emission features include C I, C II, Si I, Si II, O I, Co II, Al II, Mg II, Cr II, Fe I, and Fe II, while the photospheric absorption spectrum is dom…
Latitudinal Distribution of O 2on Ganymede: Observations with the Hubble Space Telescope
Spencer, John R.; Calvin, Wendy M.
To help constrain the spatial variation of oxygen on Jupiter's satellite Ganymede, and hence have more clues to its mode of production and stability, we have obtained spectral data from the Faint Object Spectrograph (FOS) for a single pole-to-pole latitudinal strip, along with several Wide Field Planetary Camera 2 (WFPC2) images in three narrow ba…
Spectropolarimetry and nebular geometry of the symbiotic star HBV 475.
Schild, H.; Schmid, H. M.
We present and discuss spectropolarimetry of the Raman scattered emission features at λ6825 and λ7082 of the symbiotic nova HBV 475. Meaningful interpretation in relation to the orbital phase requires an improved ephemeris and we first review available photometry and deduce a new period of 956.5d and minimum epoch at JD 2444890. The flux of the λ6…
A New Luminous Blue Variable in the Giant Extragalactic H II Region NGC 2363
Drissen, Laurent; Robert, Carmelle; Roy, Jean-René
We report the discovery of an erupting luminous blue variable (LBV) star in the giant H II region NGC 2363, the most massive star-forming region in the Magellanic irregular galaxy NGC 2366. This LBV, presently the visually brightest star in the galaxy (MV ~ -10.2), was first noticed in Hubble Space Telescope Wide Field Planetary Camera …
The O-Type Binary 15 Monocerotis Nears Periastron
Gies, Douglas R.; Penny, Laura R.; Bagnuolo, William G., Jr. +6 more
We present new radial velocity measurements for the massive binary 15 Monocerotis which indicate that the system is now very close to periastron (1996.9) in its 24 yr orbit. The velocity separation in the coming year may be large enough to permit an accurate estimate of mass ratio. We also present our first astrometric measurement of 15 Mon made w…