Search Publications
Quasar Lyman Edge Regions in Polarized Light
Antonucci, R. R. J.; Kinney, A. L.; Bushouse, H. +2 more
The standard paradigm of energy production in quasi-stellar objects (QSOs) includes an accretion disk surrounding a supermassive black hole. Two important consequences of such a disk are a feature, probably in absorption, at the Lyman edge, and significant polarization parallel to the disk plane at most viewing angles. The polarization signature c…
The IUE MEGA Campaign: Wind Structure and Variability of HD 50896 (WN5)
Willis, A. J.; Moffat, A. F. J.; Marchenko, S. V. +2 more
We present preliminary results from an extensive study of UV line and continuum variability in the WN5 star HD 50896 = EZ CMa, monitored over 16 consecutive days in 1995 January, as part of the IUE "MEGA" campaign. Although variations are seen in all the major emission lines, the clearest occur in the unsaturated, subordinate N IV lambda 1718 line…
A Test of Galaxy Evolutionary Models via Angular Sizes
Casertano, Stefano; Im, Myungshin; Tyson, J. Anthony +2 more
The relationship between angular size, magnitude, and redshift of faint galaxies is explored as a potential tool to distinguish between different galaxy evolutionary models. Different models, based on merging, mild luminosity evolution, and no evolution, lead to different predictions of the angular size distribution, redshift-size relation, and ma…
Atomic Physics with the Goddard High-Resolution Spectrograph on the Hubble Space Telescope. II. Oscillator Strengths for Singly Ionized Iron
Savage, Blair D.; Cardelli, Jason A.
Moderate-to-high signal-to-noise interstellar absorption line data, obtained with the Goddard High-Resolution Spectrograph aboard the Hubble Space Telescope toward β1 Sco, HD 18100, and µ Col, are used to derive absolute oscillator strengths (f-values) for a number of weak and strong ultraviolet resonance transitions of Fe II span…
A Hubble Space Telescope Study of the Underlying White Dwarf in the Dwarf Nova VW Hydri during Quiescence
Szkody, Paula; Sion, Edward M.; Cheng, Fu-Hua +1 more
We have analyzed a far-ultraviolet spectrum of the dwarf nova VW Hyi obtained during quiescence with the Hubble Space Telescope Faint Object Spectrograph (HST FOS). The observation occurred 10 days after the return to optical quiescence from a superoutburst of VW Hyi. The spectrum reveals a very strong Stark-broadened Ly-alpha absorption with narr…
PKS 2349-014: A Luminous Quasar with Thin Wisps, a Large Off-Center Nebulosity, and a Close Companion Galaxy
Schneider, Donald P.; Bahcall, John N.; Kirhakos, Sofia
Hubble Space Telescope (HST) images (WFC2) of PKS 2349-014 show that this luminous nearby quasar is interacting with diffuse (presumably galactic) material. Two thin wisps that have a total extent of about 20 kpc (for H0 = 100 km s-1 Mpc-1 and Omega 0 = 1.0) are observed to approximately surround the quasar. One of the wisps appears to pass throug…
High-Velocity, High-Excitation Neutral Carbon in a Cloud in the VELA Supernova Remnant
Jenkins, Edward B.; Wallerstein, George
HD 72089 is situated behind the Vela supernova remnant, and the interstellar absorption lines in the spectrum of this star are remarkable for two reasons. First, there are six distinct velocity components that span the (heliocentric) velocity range -60 to +121 km/s in the lines of Na I and Ca II. Second, two of the components at high velocity, one…
Structural Parameters of Faint Galaxies from Prerefurbishment Hubble Space Telescope Medium Deep Survey Observations
Im, M.; Griffiths, R. E.; Casertano, S. +4 more
We present a statistical study of the properties of faint galaxies from a large catalog of about 13,500 objects found in 112 random fields observed with the Hubble Space Telescope Wide Field Camera before refurbishment. The majority of the objects are faint galaxies with 18 < I < 25 mag. For each object we determine half-light radius, magnit…
Energy Release and Dissipation during Giant Solar Flares
Hurley, K.; Sommer, M.; Boer, M. +3 more
The Solar X-Ray/Cosmic Gamma-Ray Burst Experiment aboard Ulysses has observed 11 solar hard X-ray flares with effective peak counting rates greater than 4 × 105 counts s-1. We have estimated the energy dissipated during these "giant" flares (GOES class > X12). The flare on 1991 June 1, probably the largest flare of the pre…
Ultraviolet Spectropolarimetry of High-Redshift Quasars with the Hubble Space Telescope
Impey, C. D.; Malkan, Matthew A.; Webb, Wayne +1 more
Ultraviolet spectropolarimetry of three bright high-redshift low- polarization quasars (LPQs) was obtained with the Faint Object Spectrograph of the Hubble Space Telescope. Two of the quasars, PG 1634+706 and PG 2302+029, had polarizations p ~ 0.5%-1.0% throughout the ultraviolet, and showed no significant variation of polarization amplitude or po…