Search Publications
Searching for the Physical Drivers of the Eigenvector 1 Correlation Space
Marziani, P.; Zwitter, T.; Sulentic, J. W. +2 more
We recently discussed an Eigenvector 1 (E1) parameter space that provides optimal discrimination between the principal classes of broad-line active galactic nuclei (AGNs). In this paper we begin a search for the most important physical parameters that are likely to govern correlations and data point distribution in E1 space. We focus on the princi…
High-Resolution X-Ray and Ultraviolet Spectroscopy of the Complex Intrinsic Absorption in NGC 4051 with Chandra and the Hubble Space Telescope
Brandt, W. N.; Kaspi, Shai; Elvis, Martin +6 more
We present the results from simultaneous observations of the narrow-line Seyfert 1 galaxy NGC 4051 with the Chandra High Energy Transmission Grating Spectrometer and the Hubble Space Telescope Space Telescope Imaging Spectrograph. The X-ray grating spectrum reveals absorption and emission lines from hydrogen-like and helium-like ions of O, Ne, Mg,…
A Possible Massive Asteroid Belt around ζ Leporis
Jura, M.; Chen, C. H.
We have used the Keck I telescope to image at 11.7 and 17.9 µm the dust emission around ζ Leporis, a main-sequence A-type star at 21.5 pc from the Sun with an infrared excess. The excess is at most marginally resolved at 17.9 µm. The dust distance from the star is probably <=6 AU, although some dust may extend to 9 AU. The mass of o…
Tailored Analyses of the WN 8 Stars WR 40 and WR 16
Hillier, D. J.; Herald, J. E.; Schulte-Ladbeck, R. E.
We present the results of tailored spectral analyses of two WN 8 Wolf-Rayet stars: WR 40 (HD 96548) and WR 16 (HD 86161). These analyses were carried out utilizing line-blanketed non-LTE model atmospheres with provisions for a clumped wind. For the first time in WN analyses, stellar parameters are derived by attempting to match the entire observed…
Multiwavelength Monitoring of the Narrow-Line Seyfert 1 Galaxy Arakelian 564. II. Ultraviolet Continuum and Emission-Line Variability
Brandt, W. N.; Clavel, J.; Kriss, G. A. +15 more
We present results of an intensive 2 month campaign of approximately daily spectrophotometric monitoring of the narrow-line Seyfert 1 galaxy (NLS1) Ark 564 with the Hubble Space Telescope. The fractional variability amplitude of the continuum variations between 1365 and 3000 Å is ~6%, about a factor of 3 less than that found in typical Seyfert 1 g…
FUSE and Hubble Space Telescope/STIS Observations of Hot and Cold Gas in the AB Aurigae System
Deleuil, M.; Bouret, J. -C.; Roberge, A. +9 more
We present the first observations of a Herbig Ae star with a circumstellar disk by the Far-Ultraviolet Spectroscopic Explorer (FUSE) as well as a simultaneous observation of the star obtained with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (STIS). The spectra of AB Aurigae show emission and absorption features arising from gas…
Far Ultraviolet Spectroscopic Explorer Observations of Molecular Hydrogen in Translucent Interstellar Clouds. II. The Line of Sight toward HD 110432
York, Donald G.; Roueff, E.; Shull, J. Michael +7 more
We report the second study from the FUSE survey of molecular hydrogen in translucent clouds for the line of sight toward HD 110432. This star lies beyond the Coalsack dark nebula, and, with E(B-V)=0.40 and AV=1.32, this line of sight bridges the gap between less-extinguished diffuse-cloud lines of sight with AV~1, such as ζ O…
Boron Abundances in Early B Stars: Results from the B III Resonance Line in IUE Data
Proffitt, Charles R.; Quigley, Mark F.
We have used archival International Ultraviolet Explorer high-dispersion SWP spectra to study the B III resonance line at 2065.8 Å in 44 early B stars. We find a median boron abundance about half that of solar system meteoritic material, consistent with the values found from previous studies of boron in early B stars. About one-third of the stars …
New Constraints on Protostellar Jet Collimation from High-Density Gas UV Tracers
Gómez de Castro, Ana I.; Verdugo, Eva
The analysis of high-resolution profiles of the semiforbidden UV lines of C III]1908 and Si III]1892 in the spectra of T Tauri stars (TTSs) shows the following: (1) There is C III]1908 and Si III]1892 emission at velocities that are similar to those observed in the optical forbidden lines formed in the T…
On the Nature of Intrinsic Absorption in Reddened Seyfert 1 Galaxies
Kraemer, S. B.; Crenshaw, D. M.
We discuss the origin of the ``dusty lukewarm absorber,'' which we previously identified in the reddened Seyfert 1 galaxies NGC 3227 and Akn 564. This absorber is characterized by saturated UV absorption lines (C IV, N V) near the systemic velocity of the host galaxy and is likely responsible for reddening both the continuum and emission lines (in…