Search Publications
Colliding Wind Binary Systems: Monte Carlo Simulations of Line-Profile Variability
Stevens, Ian R.
We investigate the line-profile variability observed in colliding wind binary systems. In these systems the ultraviolet P Cygni line profiles show marked orbital variability; the nature of which differs between individual lines and binaries. We present results of three-dimensional Monte Carlo simulations of the radiative transfer and line formatio…
30 Doradus: Ultraviolet and Optical Stellar Photometry
Cheng, Kwang-Ping; O'Connell, Robert W.; Bohlin, Ralph C. +7 more
Stellar photometry is presented for 314 stars in a 9.7' x 9.7' field in the 30 Dor nebula centered on R136. Magnitudes are computed from Ultraviolet Imaging Telescope images in up to 4 bands with effective wave-lengths from 1615 to 2558 A, and from a ground-based CCD image in the B band. Spectral types and extinctions are estimated using a least- …
The First Detection of a Collapsed Core Globular Cluster in M31
Cacciari, C.; Federici, L.; Ferraro, F. R. +6 more
We report on the observations of a globular cluster (designated G105 = Bo 343) in the nearby spiral galaxy M 31, using the Hubble Space Telescope (HST). Image deconvolutions using three different methods indicate that this cluster has a density profile with the morphology characteristic of stellar systems which have undergone core collapse, i.e., …
A Spectroscopic Search for Colliding Stellar Winds in O-Type Close Binary Systems. III. 29 UW Canis Majoris
Wiggs, Michael S.; Gies, Douglas R.
The orbital-phase variations in the optical emission lines and UV P Cygni lines of the massive O-type binary 29 UW Canis Majoris are investigated in a search for evidence of colliding winds. High SNR spectra of the H-alpha and He I 6678-A emission lines are presented, and radial velocity curves for several features associated with the photosphere …
A Search for Proton Beams during Flares on AU Microscopii
Carpenter, K. G.; Robinson, R. D.; Maran, S. P. +1 more
We report the results of a coordinated observing campaign on the active M dwarf star AU Mic. The purpose of the campaign was to search for evidence of proton beams during the impulsive phase of stellar flares and to determine whether the energy contained in these beams represented a significant fraction of the energy budget of the flare. During a …
Forbidden Velocity Gas Detected in Ultraviolet Interstellar Absorption toward Four Distant Inner Galaxy Stars
Tripp, Todd M.; Sembach, Kenneth R.; Savage, Blair D.
We analyze International Ultraviolet Explorer high-dispersion observations of interstellar absorption toward HD 167402, HD 168941, HD 172140, and HD 173502, four distant, inner Galaxy, lower halo/thick disk stars (2°.3 < 1 < 5°.8, 6°.3 < |b| < 12°.3). On the basis of ultraviolet stellar photospheric and wind lines, we classify HD 16740…
The Distant Future of Solar Activity: A Case Study of beta Hydri. III. Transition Region, Corona, and Stellar Wind
Linsky, J. L.; Simon, T.; Ayres, T. R. +4 more
The paper investigates the secular decay of solar-type activity through a detailed comparison of the present sun with the very old solar-type star, Beta Hyi, taken as a proxy of the future sun. Analyses of successive atmospheric layers are presented, with emphasis of the outermost parts. The FUV emission lines for the transition zone are among the…
Damped Lyman-Alpha Absorption in Q0957+561A, B
Turnshek, David A.; Bohlin, Ralph C.
A series of archival IUE low-dispersion spectral observations of the double quasar Q0957 + 561A, B are analyzed. The components of this gravitationally lensed quasar are separated by ~6". Damped Lyα absorption at redshift z_abs_ = 1.3911 with neutral hydrogen column density N(H I) ~ 7 x 10^19^ cm^-2^ is present in the spectra of both the A and B c…
Evidence for Precession of the R Aquarii Jet
Hollis, J. M.; Michalitsianos, A. G.
Several models of the R Aqr northeast jet have been proposed which attempt to explain the presence of shock excitation, resulting in a confusing picture of this nearest astrophysical jet. This paper compares observations of the jet in the R Aqr system with the HST's Faint Object Camera (FOC) and radio continuum images acquired with the VLA. The fo…
Faint Object Spectrograph Spectra of the UV Emission Lines in NGC 5548: Detection of Strong Narrow Components
Crenshaw, D. Michael; Wu, Chi-Chao; Boggess, Albert
Ultraviolet spectra of the Seyfert 1 galaxy NGC 5548 were obtained with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope on 1992 July 5, when the UV continuum and broad emission lines were at their lowest ever observed level. The high resolution of the spectra, relative to previous UV observations, and the low state of NGC 5548 al…