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A multiwavelength study of LS II+34 26: a hot post-AGB star in the process of becoming a planetary nebula.
Pottasch, S. R.; de Martino, D.; Parthasarathy, M. +4 more
We present the results from a multiwavelength analysis of LS II+34 26, recently identified as a low mass post-AGB star and not a massive population I B-type star, as previously thought. We confirm that the central star is a carbon-poor post-AGB star surrounded by a very low excitation and compact nebula. Spectroscopic monitoring carried out since …
Latitudinal Variation of Aerosol Sizes Inferred from Titan's Shadow
Karkoschka, Erich; Lorenz, Ralph D.
We measured the location, size, and shape of Titan's shadow in five images taken with the Hubble Space Telescope in 1995. We inferred the altitude of Titan's optical limb at wavelengths of 337-954 nm to an accuracy of 15 km. At each wavelength, altitudes are constant north of -5° and also constant but lower south of -50° latitude, with a linear tr…
Velocity Fields in the Solar Corona during Mass Ejections as Observed with UVCS-SOHO
Romoli, M.; Naletto, G.; Modigliani, A. +20 more
This Letter presents the observations of the first two coronal mass ejections (CMEs) obtained with the Ultraviolet Coronagraph Spectrometer of SOHO. Both CMEs were observed at high spectral resolution in the ultraviolet domain. The first event on 1996 June 6-7 was observed in H I Lyα λ1216 and Lyβ λ1026, O VI λλ1032 and 1037, Si XII λλ499 and 521 …
Accurate optical-to-radio registration of Seyfert galaxies with HST images. Absolute astrometry of HST images.
Macchetto, F. D.; Capetti, A.; Lattanzi, M. G.
We propose a method to obtain accurate absolute astrometry of Hubble Space Telescope images. Ground based images are used to link HST images to standard astrometric stars defining the optical frame of reference. The method has been used to register optical images of the Seyfert 2 galaxy NGC 5929 to the corresponding radio maps, allowing the explor…
NOTE: an HST Search for Magnesium in the Lunar Atmosphere
Parker, Joel Wm.; Stern, S. Alan; Mendillo, Michael +5 more
In October 1996 we used the Hubble Space Telescope's Faint Object Spectrograph to make the first-ever mid-ultraviolet spectroscopic search for emissions from the lunar atmosphere. This spectrum revealed no emission lines, despite the fact that strong resonance emission transitions from the Al, Si, and Mg neutrals and from Mg+occur in th…
The discovery of a new massive O-type close binary: tau CMa (HD 57061), based on HIPPARCOS and Walraven photometry
van Leeuwen, F.; van Genderen, A. M.
We present an interpretation of Hipparcos Hp and Walraven VBLUW photometry of the brightest star in the open cluster NGC 2362 (although not necessarily associated with this cluster), HD 57061 (30tau CMa, HR 2782, HIP 35415). In this multiple system the central component consist of a visual double star, two O-type stars separated by 0\farcs 151, wh…
Zero-metallicity very low mass stars as halo dark matter.
Kerins, E. J.
Hubble Space Telescope (HST) limits on the amount of halo dark matter (DM) in the form of very low-mass (VLM) stars close to the hydrogen-burning limit have been interpreted as excluding such stars as viable candidates. However, these limits assume that the stars are smoothly distributed and have at least the metallicity of Population II stars, wh…
Ultraviolet Spectral Morphology of the Stellar Core of eta Carinae
Walborn, Nolan R.; Ebbets, Dennis C.; Parker, Joel Wm.
We present high-quality spectra of eta Car between 1203 and 1765 A obtained with the Goddard High Resolution Spectrograph on board the Hubble Space Telescope. A square entrance slit 0."22 in diameter was used to isolate the brightest region of the core, "component A," from the nearby knots of ejecta and the nebulosity in which it is embedded. The …
Sounding the Sun's Chromosphere
Duvall, T. L., Jr.; Shibahashi, H.; Jefferies, S. M. +3 more
Time-distance analysis of solar acoustic waves with frequencies above the nominal atmospheric acoustic cutoff frequency (~5.3 mHz) shows partial reflection of the waves at both the Sun's photosphere and a layer located higher in the atmosphere. This result supports recent reports of chromospheric modes.
Atomic Data for the Re II UV 1 Multiplet and the Rhenium Abundance in the HgMn-type Star χ Lupi
Wahlgren, Glenn M.; Lawler, J. E.; Leckrone, David S. +5 more
We report new laboratory spectroscopic analyses that have been conducted to acquire wavelength and oscillator strength data for lines of the Re II UV 1 multiplet. Wavelengths were determined to a sub-milliangstrom accuracy for the hyperfine and isotopic structure components from laboratory spectra obtained with the Lund VUV Fourier Transform Spect…