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Ultraviolet variability of NGC 4151 : a study using principal component analysis.
Penston, M. V.; Snijders, M. A. J.; Mittaz, J. P. D.
In an attempt at a decomposition of the different sources of variation in the spectra of NGC 4151, we have carried out a principal component analysis of spectra, seeking the number and form of the significant linearly independent spectra that are needed to reconstruct the data within the errors. Methods are outlined with particular emphasis on the…
Ultraviolet Interstellar Absorption toward HD 163522, a Halo Star at 9 Kiloparsecs in the Direction L = 350 and B = -9
Savage, Blair D.; Sembach, Kenneth; Massa, Derck
UV interstellar absorption line measurements obtained by the IUE satellite toward HD 163522 in the direction l = 349.6 deg and b = -9 deg are analyzed. The UV stellar spectrum of HD 163522 places the star beyond the Galactic center at a distance away from the Galactic plane of z = -1.5 kpc. An absorption-line spectrum with S/N approximately equal …
The mass ratio of nu SGR from ultraviolet radial velocities.
Jeffery, C. S.; Dudley, R. E.
The first positive determination of the secondary orbit of the hydrogen-deficient binary υ Sgr has been achieved by the application of cross-correlation methods to high-resolution ultraviolet (UV) spectra obtained with IUE. The mass ratio thus obtained (q = 0.63±0.01) and the consequent minimum mass for the primary (Mp sin3i/…
Ultraviolet spectra of a large sample of quasars - II. Variability ofLy-alpha and C IV emission lines.
Gondhalekar, P. M.
The analysis of spectra of 34 quasars observed more than once with IUE is presented. The Lyα + N V and C IV emission lines in the spectra of some quasars in this sample change in intensity over a short time-scale. This time-scale is comparable to the time-scale for change observed in the intensity of emission lines in the spectra of low-luminosity…
A Multiwavelength Study of the Carlson-Henize Sample of Early-Type Galactic Extreme Emission-Line Stars
Feldman, P. D.; Shore, Steven N.; Brown, Douglas N. +3 more
A UV, optical, and radio study of nine early spectral type extreme emission-line Galactic stars from the Carlson and Henize (1979) sample is presented. He 3-407 and He 3-1482 appear to be analogs of the massive evolved B(e) and luminous blue variable stars of the Magellanic Clouds. The sample appears to be confined to a narrow range in spectral ty…
The Mass of the Classical Cepheid SU Cygni
Bolton, C. T.; Evans, Nancy Remage
Velocities of the companion of the classical Cepheid SU Cyg have been measured from 13 IUE high-dispersion spectra. Because the companion is itself a member of a short-period binary system, its short-period orbit and the orbital amplitude of the center of mass in the long-period system are determined from a triple system solution. The velocity amp…
Ionization in Nearby Interstellar Gas
Frisch, P. C.; York, D. G.; Fowler, J. R. +1 more
Due to dielectric recombination, neutral magnesium represents an important tracer for the warm low-density gas around the solar system. New Mg I 2852 absorption-line data from IUE are presented, including detections in a few stars within 40 pc of the sun. The absence of detectable Mg I in Alpha CMa and other stars sets limits on the combined size …
On the Spectrum and Field Strength of the Magnetic White Dwarf GD 229
Foltz, Craig B.; Schmidt, Gary D.; Latter, William B.
The broad-coverage optical spectrum obtained for the strongly polarized magnetic white dwarf GD 229 reveals additional as well as apparent changes in the locations of known absorption features; the latter are ostensibly due to star rotation in the decade since the last published spectrum. Since (1) the spectrum of magnetized hydrogen is not consis…
Ultraviolet and Optical Spectroscopy of NGC 5548 and the Nature of the Broad-Line Region
Peterson, Bradley M.; Reichert, Gail A.; Korista, Kirk T. +1 more
The structure of the broad-line region in NGC 5548 is investigated by analysis of the integrated flux and profile variations observed in optical and ultraviolet emission lines. It is shown that the observations do not appear to be consistent with models which identify the variable part of the emission lines with a simple rotating disk structure. T…
The Fe V/Fe VI ionization structure in WNE Wolf-Rayet winds.
Koenigsberger, G.
An analysis of the phase-dependent intensity variations of the Fe IV, V, and VI pseudocontinua in four WNE binary systems having different orbital separations is used to obtain information regarding the ionization and velocity structures of the wind of the WR component. The ratio of Fe VI/Fe V decreases in strength as a function of distance from t…