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Nearby Young Dwarf Galaxies: Primordial Gas and Lyα Emission
Thuan, Trinh X.; Izotov, Yuri I.
We present Hubble Space Telescope UV spectrophotometry of three extremely metal-deficient blue compact dwarf (BCD) galaxies, SBS 0335-052 (Z ~ Z⊙/40), Tol 65 (Z ~ Z⊙/24), and T1214-277 (Z ~ Z⊙/23). Broad damped Lyα absorption is seen in the first two BCDs. For SBS 0335-052, the H I column density derived by fitting…
The Nuclear Stellar Core, the Hot Dust Source, and the Location of the Nucleus of NGC 1068
Genzel, R.; Maiolino, R.; Quirrenbach, A. +2 more
We present new near-infrared speckle and adaptive optics imaging and integral field spectroscopy of the nuclear region of NGC 1068. Ninety-four percent of the K-band light in the central 1" originates from a <=30 milliarcsecond diameter source whose position we determine to coincide within +/-0.15" with the apex of the cone structure seen in th…
Turbulent Velocities and Ion Temperatures in the Solar Corona Obtained from SUMER Line Widths
Wilhelm, K.; Curdt, W.; Schühle, U. +3 more
Turbulent plasma velocities and ion temperatures were determined from the line widths recorded by the Solar Ultraviolet Measurements of Emitted Radiation instrument on the Solar and Heliospheric Observatory spacecraft. From the widths of the lines of five light elements (Ne, Na, Mg, Si, and S) and a heavy element (Fe), it was possible to determine…
Local Interstellar Medium Properties and Deuterium Abundances for the Lines of Sight toward HR 1099, 31 Comae, β Ceti, and β Cassiopeiae
Wood, Brian E.; Linsky, Jeffrey L.; Dempsey, Robert C. +2 more
We analyze Goddard High-Resolution Spectrograph data to infer the properties of local interstellar gas and the deuterium/hydrogen (D/H) ratio for lines of sight toward four nearby late-type stars--HR 1099, 31 Comae, β Ceti, and β Cassiopeiae. The data consist of spectra of the hydrogen and deuterium Lyα lines, and echelle spectra of the Mg II h an…
Hubble Space Telescope Imaging of Compact Steep-Spectrum Radio Sources
Golombek, D.; Sparks, W. B.; Macchetto, F. +8 more
We present Hubble Space Telescope WFPC2 images taken through a broad red filter (F702W) of 30 Third Cambridge Catalog compact steep spectrum (CSS) radio sources. We have overlaid radio maps taken from the literature on the optical images to determine the radio-optical alignment and to study detailed correspondence. All CSS sources for which the re…
Peculiar Multimodality on the Horizontal Branch of the Globular Cluster NGC 2808
Rich, R. Michael; Renzini, Alvio; Piotto, Giampaolo +6 more
We present distributions of colors of stars along the horizontal branch (HB) of the globular cluster NGC 2808, from Hubble Space Telescope Wide Field Planetary Camera 2 imaging in B, V, and an ultraviolet filter (F218W). This cluster's HB is already known to be strongly bimodal, with approximately equal-sized HB populations widely separated in the…
Performance and Early Results from the GOLF Instrument Flown on the SOHO Mission
Baudin, F.; Christensen-Dalsgaard, J.; García, R. A. +21 more
GOLF in-flight commissioning and calibration was carried out during the first four months, most of which represented the cruise phase of SOHO towards its final L1 orbit. The initial performance of GOLF is shown to be within the design specification, for the entire instrument as well as for the separate sub-systems. Malfunctioning of the polarising…
Wind variability of B supergiants. III. Corotating spiral structures in the stellar wind of HD 64760.
Owocki, S. P.; Cranmer, S. R.; Prinja, R. K. +2 more
Fourier analysis of two spectroscopic time series obtained with the IUE observatory confirm that the ultraviolet stellar wind profiles of HD 64760 (B0.5 Ib) are periodically variable. The periodic component consists of modulations that extend over most of the P Cygni absorption trough, and can frequently be traced through the emission lobe. The mo…
First View of the Extended Green-Line Emission Corona At Solar Activity Minimum Using the Lasco-C1 Coronagraph on SOHO
Llebaria, A.; St. Cyr, O. C.; Plunkett, S. P. +21 more
The newly developed C1 coronagraph as part of the Large-Angle Spectroscopic Coronagraph (LASCO) on board the SOHO spacecraft has been operating since January 29, 1996. We present observations obtained in the first three months of operation. The green-line emission corona can be made visible throughout the instrument's full field of view, i.e., fro…
The Hubble Space Telescope Extragalactic Distance Scale Key Project. VII. The Discovery of Cepheids in the Leo I Group Galaxy NGC 3351
Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +20 more
We report of the discovery and properties of Cepheid variable stars in the barred spiral galaxy NGC 3351 which is a member of the Leo I group of galaxies. NGC 3351 is one of 18 galaxies being observed as part of the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale which aims to determine the Hubble constant to 10% accur…