Search Publications
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…
Winds in Central Stars of Planetary Nebulae
Modigliani, A.; Patriarchi, P.; Perinotto, M.
We studied five central stars of planetary nebulae with IUE high-resolution spectra to determine the wind properties of their central stars. Using the best stellar and nebular parameters, and analyzing the P Cygni profiles seen in lines of the ions C IV, N V, N IV, O V, O IV, and Si IV with the SEI method, we have obtained the following values of …
The Hydrogen Lyman-Alpha Emission of Capella
Ayres, Thomas R.; Linsky, Jeffrey L.; Gayley, K. G. +1 more
We describe the hydrogen Ly-alpha emission of the spectroscopic binary Capella (G8 III + GO III) recorded at 0.1 A resolution by the International Ultraviolet Explorer. The overt changes in the composite line shape with orbital phase are controlled by the active GO III star and permit a dissection of the stellar components despite the obliteration…
X-Ray Light Curves of Active Galactic Nuclei Are Phase Incoherent
Done, Chris; Krolik, Julian; Madejski, Grzegorz
We compute the Fourier phase spectra for the light curves of five low- luminosity active galactic nuclei observed by EXOSAT. There is no statistically significant phase coherence in any of them. This statement is equivalent, subject to a technical caveat, to a demonstration that their fluctuation statistics are Gaussian. Models in which the X-ray …