Search Publications
Ultraviolet Absorption Lines from High-Velocity Gas in the VELA Supernova Remnant: New Insights from Space Telescope Imaging Spectrograph Echelle Observations of HD 72089
Kaiser, Mary Elizabeth; Tripp, Todd M.; Jenkins, Edward B. +12 more
The star HD 72089 is located behind the Vela supernova remnant and shows a complex array of high- and low-velocity interstellar absorption features arising from shocked clouds. A spectrum of this star was recorded over the wavelength range 1196.4-1397.2 Å at a resolving power of λ/Δλ = 110,000 and a signal-to-noise ratio of 32 by the Space Telesco…
High-Temperature Lines in SUMER Spectra Recorded Above a Bright Solar Active Region
Wilhelm, K.; Curdt, W.; Schühle, U. +3 more
We identify spectral lines emitted by solar abundant elements due primarily to transitions within the 2s22pk and 3s23pk (where k = 1, 5) ground configurations of ions that are formed in ionization equilibrium between 2 × 106 and 8 × 106 K. The transitions were identified in spectra …
Atomic Carbon in ARP 220
Gerin, Maryvonne; Phillips, Thomas G.
We present detections of the 3P1-3P0 fine-structure line of neutral carbon and of the J=3-2 rotational line of carbon monoxide in the ultraluminous infrared galaxy Arp 220, obtained at the Caltech Submillimeter Observatory. C I emission in Arp 220 is found to be at the expected level in relation to the s…
Broad Emission Line Variability as a Constraint upon the Physical Conditions within the Broad Emission Line Region of NGC 5548
Goad, Mike; Koratkar, Anuradha
Using a Gaussian fitting procedure, we have constructed an accurate UV narrow emission line template spectrum for the Seyfert 1 galaxy NGC 5548, from the low-state Hubble Space Telescope/Faint Object Spectrograph UV spectrum taken on 1982 July 5 with the 1.0" circular aperture. This template spectrum is similar in form to that determined for the p…
The Si/Ne Abundance Ratio in Polar Coronal Hole and Quiet-Sun Coronal Regions
Wilhelm, K.; Schühle, U.; Lemaire, P. +4 more
Using spectra obtained from the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer flown on the Solar and Heliospheric Observatory (SOHO) spacecraft, we determine the Si/Ne abundance ratio in diffuse, interplume polar coronal hole regions, as well as the ratio relative to quiet-Sun coronal regions. Ne has the second highest f…
The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XII. The Discovery of Cepheids and a New Distance to NGC 2541
Illingworth, Garth D.; Madore, Barry F.; Freedman, Wendy L. +17 more
We report the detection of Cepheids and a new distance to the spiral galaxy NGC 2541, based on data obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope (HST). A total of 25 exposures (divided into 13 epochs) were obtained using the F555W filter (transformed to Johnson V), and nine exposures were obtained (divided in…
A Spherical Non-LTE Line-blanketed Stellar Atmosphere Model of the Early B Giant epsilon Canis Majoris
Hauschildt, P. H.; Baron, E.; Shore, S. N. +1 more
We use a spherical non-LTE fully line-blanketed model atmosphere to fit the full multiwavelength spectrum, including the extreme-ultraviolet (EUV) continuum observed by the Extreme Ultraviolet Explorer, of the B2 II star ɛ Canis Majoris (CMa). The available spectrophotometry of ɛ CMa from 350 Å to 25 µm is best fitted with model parameters T…
ORFEUS II Far-Ultraviolet Observations of 3C 273: Interstellar and Intergalactic Absorption Lines
Krautter, Joachim; Bowyer, Stuart; Hurwitz, Mark +7 more
We present the first intermediate-resolution (λ/Δλ = 3000) spectrum of the bright quasi-stellar object 3C 273 at wavelengths between 900 and 1200 Å. Observations were performed with the Berkeley spectrograph aboard the ORFEUS II mission. We detect Lyβ counterparts to intergalactic Lyα features identified by Morris and coworkers at cz = 19,900, 160…
Theoretical Oscillator Strengths for Sr II and Y III, with Application to Abundances in the HgMn-Type Star χ Lupi
Wahlgren, Glenn M.; Proffitt, Charles R.; Brage, Tomas +2 more
Oscillator strengths for selected transitions of Sr II and Y III have been determined using ab initio multiconfiguration Hartree-Fock techniques. The importance of including an accurate treatment of the core-valence correlation is emphasized. The results are used to determine the abundances of Sr and Y in the chemically peculiar star χ Lupi from H…
Broad Ne VIII λ774 Emission from Quasars
Hamann, Fred; Cohen, Ross D.; Shields, Joseph C. +3 more
Ne VIII λ774 is an important tracer of the high-ionization gas in QSOs. We examine the Ne VIII emission-line properties using new Hubble Space Telescope (HST)-FOS spectra of four sources, mean spectra derived from two QSO samples in the HST archives, and new photoionization calculations. The results support our previous claim that broad Ne VIII li…