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The Intermediate Stellar Mass Population in the M31 OB Association NGC 206
Lynds, Roger; O'Neil, Earl J., Jr.; Baum, William A. +1 more
As part of our effort to determine what affects the star formation process by looking at the products of that process, we have obtained broadband Hubble Space Telescope images of the large OB association NGC 206 in the nearby spiral galaxy M31. Our images cover approximately the southern half of the association. We have detected stars down to an F…
Ultraviolet Spectroscopy of the DBV White Dwarf Star GD 358
Provencal, J. L.; Shipman, H. L.; Thejll, P. +2 more
We report on analysis of UV spectra of the DBV GD 358 obtained with the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope (HST). We confirm the detection of He II (1640 Å) and C II (1335 Å) reported by Sion et al. in 1988. The He II feature indicates a temperature of 27000±1000 K, somewhat higher than previous estimates…
The beta Pictoris Phenomenon in A-Shell Stars: Detection of Accreting Gas
Talavera, A.; England, M. N.; McCollum, B. +4 more
We present the results of an expanded survey of A-shell stars using IUE high-dispersion spectra and find accreting, circumstellar gas in the line of sight to nine stars, in addition to the previously identified beta Pic, HR 10, and 131 Tau, which can be followed to between +70 and 100 km s-1 relative to the star. Two of the program stars, HD 88195…
Goddard High Resolution Spectrograph Observations of Variability in the RS Canum Venaticorum System V711 Tauri (HR 1099)
Brown, Alexander; Neff, James E.; Linsky, Jeffrey L. +4 more
Goddard High Resolution Spectrograph (GHRS) observations of the RS CVn-type binary V711 Tau (K1 IV + G5 IV) were obtained at several phases over two consecutive stellar orbital cycles in order to study ultraviolet emission-line profile and flux variability. Spectra cover the Mg II h and k lines, C IV doublet, and Si IV region, as well as the densi…
HST Imaging Polarimetry of the Seyfert 2 Galaxy NGC 5728
Boksenberg, A.; Capetti, A.; Sparks, W. B. +2 more
We present the results of HST imaging polarimetry of NGC 5728 taken with the COSTAR corrected Faint Object Camera in the ultraviolet (3000- 3700 A) and covering the region interior to its well-known nuclear ring. The total intensity image is dominated by a bright extended core, 1" x 0.7" in size, which is resolved into a large number of compact kn…
Relations between the Optical Fe II Emission and Ultraviolet Spectra in Active Galactic Nuclei
Wang, Ting-Gui; Zhou, You-Yuan; Gao, An-Song
Optical Fe II emission is a general characteristic of most active galactic nuclei, but the physical conditions in the Fe II-emitting region are not yet understood. The current photoionization models underpredict the total Fe II intensity as well as optical Fe II/Hβ ratio. In this paper, we report the results of a statistical analysis of the relati…
Pulsations and Line Profile Changes in the Ultraviolet Spectrum of Hercules X-1: Results from a Multiwavelength Campaign
Nagase, Fumiaki; Vrtilek, S. D.; McCray, Richard +2 more
We report simultaneous X-ray and ultraviolet observations of the X-ray binary pulsar Hercules X-1, obtained over nearly half of a 1.7 day binary orbit using the ASCA X-ray telescope and the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope. The GHRS resolved, for the first time, two moving emission components. One featu…
The Ultraviolet Spectrum of DQ Herculis: Detection of Line and Continuum Pulsation
Anderson, Scott F.; Margon, Bruce; Downes, Ronald A. +1 more
The old nova DQ Herculis was observed with the Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) in the 1150-2500 Å range. Spectra were taken with a time resolution of 4.08 s, allowing a search for pulsations of the UV light at the 71 s white dwarf spin period, analogous to those long known to be present in visible light. The integrated…
Anticorrelation of Variability Amplitude with X-Ray Luminosity for Active Galactic Nuclei
Abramowicz, Marek A.; Bao, Gang
The bright-spot model for the short-term X-ray variability of active galactic nuclei predicts that, statistically, sources with larger luminosities should have smaller variability amplitudes. This quantitatively agrees with the analysis of the observational data from 12 high-quality EXOSAT long looks performed by Lawrence & Papadakis.
Damped LY alpha Absorbers as Tracers of the Evolution of the Mass Spectrum of Interstellar Matter in the Galaxy Population
Turnshek, David A.; Khersonsky, Valery K.
A generally accepted approach to the interpretation of the damped Lyα absorption systems seen in QSO spectra is to attribute them to cases in which the observer's sight line passes through high column density gaseous disks of galaxies, i.e., spiral galaxies or the progenitors of spirals. Here we consider an alternative natural possibility, consist…