Search Publications
Do First Results from SOHO UVCS Indicate That the Solar Wind Is Accelerated by Solitary Waves?
Davila, J. M.; Ofman, L.
The Ultraviolet Coronagraph Spectrometer (UVCS) on board the recently launched US-European Solar and Heliospheric Observatory (SOHO) satellite has found O VI and H I emission lines with a broad component that corresponds to ~300 km s-1 unresolved motions at about 0.7 solar radii above the photosphere. These motions appear to be independ…
The luminosity function of the globular cluster NGC 6752 with the Hubble Space Telescope: evidence of mass segregation
Bragaglia, A.; Carretta, E.; Ferraro, F. R. +2 more
We present the luminosity function (LF) for the lower main sequence of the Galactic globular cluster NGC6752, as obtained from Hubble Space Telescope (HST) observations centred 2 arcmin from the cluster centre. We present data in the F814W and F555W filters. Our LF reaches down to M_I=11 or, translated to a mass function, to M~=0.12 Msolar. The LF…
Detailed Lensing Properties of the MS 2137-2353 Core and Reconstruction of Sources from Hubble Space Telescope Imagery
Le Fèvre, O.; Hammer, F.; Luppino, G. A. +3 more
A deep HST image of the core of the cluster of galaxies MS 2137-2353 has revealed detailed morphological structures in two arc systems, which are modeled and well reproduced. An analysis of the lensing properties of the dark matter component indicates that the cluster could have a mass distribution almost as simple as a single elliptical mass dist…
The Nuclear Ionized Gas in the Radio Galaxy M84 (NGC 4374)
Heckman, Timothy M.; Bower, Gary A.; Wilson, Andrew S. +1 more
We present optical images of the nucleus of the nearby radio galaxy M84 (NGC 4374 = 3C 272.1) obtained with the Wide Field/Planetary Camera 2 aboard the Hubble Space Telescope. Our three images cover the Hα + [N II] emission lines as well as the V and I continuum bands. Analysis of these images confirms that the Hα + [N II] emission in the central…
Fractionated stellar wind - the example of σ Orionis E.
Groote, D.; Hunger, K.
In main-sequence stars, at effective temperatures below =~20000K, radiation ceases to be able to drive a stellar wind. In a rather narrow transition regime, elemental segregation seems possible due to the decoupling of He and, under special circumstances, also of H from the absorbing metal ions in the wind. This effect may even be more pronounced,…
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 …