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Fundamental parameters of Wolf-Rayet stars. I. Ofpe/WN9 stars.
Hillier, D. J.; Crowther, P. A.; Smith, L. J.
A detailed study has been carried out for 4 LMC Ofpe/WN9 (`slash') stars, and the sole Galactic WN9 star WR108 (HDE 313846), using new high S/N spectroscopy and archive UV and near-IR spectroscopy. Our observations reveal that photospheric Of features such as HeIIλ4542 are absent from the optical spectra of our sampled stars. All observed optical …
Detection of massive forming galaxies at redshifts z>l
Cowie, Lennox L.; Hu, Esther M.; Songaila, Antoinette
THE complex problem of when and how galaxies formed has only recently become susceptible to direct attack. It has been known for some time that the excess of blue galaxies counted at faint magnitudes1á¤-5 implies that a considerable fraction of the massive-star formation in the Universe occurred at redshift z < 3 (refs 6, 7); but sur…
The Massive Stars of I ZW 18 as Seen in Hubble Space Telescope Images
Hunter, Deidre A.; Thronson, Harley A., Jr.
Blue compact dwarf galaxies are tiny galaxies that are dominated by intense star-forming regions. Thus, they have been thought to represent a different and extreme environment for star formation compared to the Milky Way and many other nearby galaxies. In this paper we use images obtained with the Hubble Space Telescope to resolve the main body of…
The Hubble Space Telescope Quasar Absorption Line Key Project. V. Redshift Evolution of Lyman Limit Absorption in the Spectra of a Large Sample of Quasars
Turnshek, David A.; Schneider, Donald P.; Steidel, Charles C. +10 more
Using a sample of 119 QSOs, containing objects we have selected having previously available high quality ground-based and IUE spectral observations, together with Hubble Space Telescope (HST) observations of 26 QSOs from Bahcall et al. (1993, 1995) and Impey et al. (1995) and new optical observations of 41 objects by Steidel & Sargent (1995), …
The white dwarf in AM Herculis.
Gänsicke, B. T.; Beuermann, K.; de Martino, D.
We present orbital phase-resolved UV spectroscopy of AM Herculis in its high and low state obtained with the IUE satellite. We derive the effective temperatures and sizes of the accretion-heated polecap in both states. We also estimate the effective temperature and radius of the white dwarf. The spot is hotter in the high state, but always covers …
The IUE MEGA Campaign: Wind Variability and Rotation in Early-Type Stars
Koenigsberger, G.; Howarth, I. D.; Owocki, S. P. +30 more
Wind variability in OB stars may be ubiquitous, and a connection between projected stellar rotation velocity and wind activity is well established. However, the origin of this connection is unknown. To probe the nature of the rotation connection, several of the attendees at the workshop on Instability and Variability of Hot-Star Winds drafted an I…
Kinetic Properties of Heavy Ions in the Solar Wind From SWICS/Ulysses
Geiss, J.; Galvin, A. B.; Gloeckler, G. +1 more
The kinetic properties of heavy ions in the solar wind are known to behave in a well organized way under most solar wind flow conditions: Their speeds are all equal and faster than that of hydrogen by about the local Alfvén speed, and their kinetic temperatures are proportional to their mass. The simplicity of these properties points to a straight…
The RIASS Coronathon: Joint X-Ray and Ultraviolet Observations of Normal F--K Stars
Schmitt, J. H. M. M.; Ayres, Thomas R.; Mas-Hesse, J. M. +21 more
Between 1990 August and 1991 January the ROSAT/IUE All Sky Survey (RIASS) coordinated pointings by the International Ultraviolet Explorer (IUE) with the continuous X-ray/EUV mapping by the Roentgensatellit (ROSAT). The campaign provided an unprecedented multiwavelength view of a wide variety of cosmic sources. We report findings for F-K stars, a l…
The Local LY alpha Forest: Association of Clouds with Superclusters and Voids
Carilli, Chris; Donahue, Megan; Shull, J. Michael +2 more
The Goddard High Resolution Spectrograph aboard the Hubble Space Telescope was used with the G160M grating to obtain high-resolution (0.2 Å) spectra of three very bright active galactic nuclei located behind voids in the nearby distribution of bright galaxies (i.e., CfA and Arecibo redshift survey regions). A total of eight definite (≥ 4 σ) Lyα ab…
Very Low Mass Stars and White Dwarfs in NGC 6397
Paresce, Francesco; de Marchi, Guido; Romaniello, Martino
Deep Wide Field/Planetary Camera 2 (WFPC2) images in wide bands centered at 606 and 802 nm were taken with the Hubble Space Telescope (HST) 4.6 min from the center of the galactic globular cluster NGC 6397. The images were used to accurately position approximately 2120 stars detected in the field on a color magnitude diagram down to a limiting mag…