Search Publications
The Evolution of Ultraviolet Emission Lines From Circumstellar Material Surrounding SN 1987A
Cassatella, Angelo; Gilmozzi, Roberto; Fransson, Claes +5 more
The presence of narrow high-temperature emission lines from nitrogen-rich gas close to SN 1987A has been a principal observational constraint on the evolutionary status of the supernova's progenitor. A new analysis of the complete 5 year set of low- and high-resolution IUE ultraviolet spectra of SN 1987A (1987.2-1992.3) provides fluxes for the N V…
Observations and Theoretical Implications of GRB 970228
Reichart, Daniel E.
GRB 970228 is the first gamma-ray burst (GRB) for which prolonged postburst transient X-ray, optical, and infrared emission has been detected. Recent Hubble Space Telescope (HST) observations show that the transient consists of two components: a point source, which is known to be fading, and an extended source, which is possibly fading. I fit stan…
Electron Density Diagnostics for the Solar Upper Atmosphere from Spectra Obtained by SUMER/SOHO
Wilhelm, K.; Curdt, W.; Schühle, U. +3 more
We evaluate the electron density in various solar regions above the limb observed by the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) instrument on SOHO. We find in general good agreement among line ratios from Be-, B-, N-, and Mg-like ions, giving densities of order 108 cm-3.
Optical Spectroscopy of EZ Canis Majoris: Indication for Large-Scale Structures in a Wolf-Rayet Wind
St-Louis, Nicole; Morel, Thierry; Marchenko, Sergey V.
We have carried out optical spectroscopy of the Wolf-Rayet star EZ CMa during 20 consecutive nights in 1995 January in support of the IUE Mega-project. In parallel with this optical spectroscopy, we also monitored EZ CMa using narrowband photometry. The light curve was found to be remarkably stable when folded with the \Pscr=3.77 day period, and i…
A Massive Cluster of Galaxies at Z = 0.996
Dickinson, M.; Le Fèvre, O.; Crampton, David +1 more
We report the identification of a cluster of galaxies around the high-redshift radio galaxy 3CR 184 at z = 0.996. The identification is supported by an excess of galaxies observed in projection in I-band images (both in ground-based and Hubble Space Telescope [HST] data), a peak in the redshift distribution comprising 11 galaxies (out of 56 with m…
O Stars in Transition. II. Fundamental Properties and Evolutionary Status of Ofpe/WN9 Stars from HST Ultraviolet Observations
Moffat, Anthony F. J.; Leitherer, Claus; Schmutz, Werner +4 more
We present new HST/FOS ultraviolet spectroscopic observations of seven LMC Ofpe/WN9 stars. We find that Ofpe/WN9 stars have slow winds with terminal velocities of about 400 km s-1 and high mass-loss rates of the order of 2-5 × 10-5 M⊙ yr-1. Ofpe/WN9 stellar temperatures and radii are in the range 30,000-…
The Green Line Corona and Its Relation to the Photospheric Magnetic Field
Michels, D. J.; Schwenn, R.; Howard, R. A. +8 more
Images of the green line corona made with the LASCO C1 coronagraph on SOHO are analyzed by applying current-free extrapolations to the observed photospheric field. The Fe XIV λ5303 emission is shown to be closely related to the underlying photospheric field strength. By modeling the observed intensity patterns as a function of latitude and height …
Hubble Space Telescope Observations of the Dwarf Nova WZ Sagittae: A Very Rapidly Rotating White Dwarf
Szkody, Paula; Sion, Edward M.; Cheng, F. H. +1 more
We present Hubble Space Telescope Goddard High-Resolution Spectrograph G140L spectra of the white dwarf in WZ Sge, exposed during quiescence. Our best-fitting synthetic spectra yield a rapidly rotating white dwarf with velocity Vrot sin i = 1200+300-400 km s-1, white dwarf effective temperature Twd<…
Ultraviolet Emission-line Ratios of Cataclysmic Variables
Kallman, Timothy R.; Mauche, Christopher W.; Lee, Y. Paul
We present a statistical analysis of the ultraviolet emission lines of cataclysmic variables (CVs) based on ~430 ultraviolet spectra of 20 sources extracted from the International Ultraviolet Explorer Uniform Low Dispersion Archive. These spectra are used to measure the emission-line fluxes of N V, Si IV, C IV, and He II and to construct diagnosti…
Adaptive Optics Infrared Imaging Polarimetry and Optical HST Imaging of Hubble's Variable Nebula (R Monocerotis/NGC 2261): A Close Look at a Very Young Active Herbig Ae/Be Star
Fazio, G. G.; Hora, J. L.; Close, L. M. +7 more
We present high-resolution (FWHM = 0.2") near-IR (J, H, and K') adaptive optics images of the Herbig Ae/Be star R Monocerotis. Optical Hubble Space Telescope (HST) WFPC2 PC camera archival images are also presented. For the first time, adaptive optics was utilized to make high-resolution (FWHM = 0.2") IR-imaging polarimetry maps of R Mon. In addit…