Search Publications
Quasar H-beta profiles and discs.
Penston, M. V.; Perez, E.; Jackson, N.
We present high signal-to-noise spectra of the Hβ region of eight radio-loud quasars in an investigation seeking evidence for the emission of this line from a disc. Although we do not find the double-humped profile expected in simple versions of the disc hypothesis, we do find shoulders in the profile expected in a modified form of this idea. A mo…
Short-Term X-Ray Variability of the BL Lacertae Object PKS 2155-304: Power Spectrum and Cross-Correlation Analysis
Maraschi, L.; Tagliaferri, G.; Stella, L. +2 more
We present a detailed power spectrum and cross-correlation analysis of the X-ray light curves of the BL Lac object PKS 2155 - 304, obtained with EXOSAT. The power spectra show a marked red noise-type variability, with the power increasing steeply toward low frequency. The variability is more pronounced in the 1-6 keV band than in the 0.1-2 keV ban…
A study of the flaring and quiscent X-ray and UV emission from II Pegasi.
Tagliaferri, G.; White, N. E.; Doyle, J. G. +3 more
An investigation has been conducted of the rotational modulation of the transition-region UV and coronal X-ray emission for the RS CVn system II Pegasi. The X-ray light curve is dominated by a strong flare detected at orbital phase, where the minimum of the photometric wave occurred. The flare parameters derived show that the flare originates with…
First Results from the Faint Object Camera: Imaging the Core of R Aquarii
Boksenberg, A.; Barbieri, C.; Weigelt, G. +16 more
The Faint Object Camera on the HST was pointed toward the symbiotic long-period M7e Mira variable R Aquarii, and very high resolution images of the inner core, mainly in the ionized oxygen emission lines in the optical, are reported. Both images show bright arcs, knots, and filaments superposed on a fainter, diffuse nebulosity extending in a gener…
Inefficient Accretion by the DA2 White Dwarf in V471 Tauri
Mullan, D. J.; Sion, E. M.; Shipman, H. L. +1 more
The results are reported of an analysis of eight-high-resolution International Ultraviolet Explorer (IUE) short-wavelength primary spectra of V471 Tauri, an eclipsing-spectroscopic, precataclysmic binary in the Hyades. The coaddition in velocity space of regions surrounding principle high- and low-excitation ion species on a common velocity scale …
The current ability of HST to reveal morphological structure in medium-redshift galaxies.
Bershady, Matthew A.; Seitzer, Patrick; Keel, William C. +6 more
The capabilities of the Faint Object Camera (FOC) and the Wide Field Camera (WFC) are assessed on the basis of a brief program of single-orbit images of medium-faint galaxies. The FOC yielded a good resolved image of a compact galaxy at a blue magnitude J of 20.5 in a single-orbit exposure. WFC images have a survey capability that can include many…
High-Resolution IUE Spectra of the Nova-like Variable IX Velorum
Mauche, Christopher W.
The paper addresses two separate but related studies utilizing high-resolution ultraviolet spectra of the nova-like variable IX Velorum, obtained by the IUE satellite. The observations used in the studies are described, and the velocity offsets of the broad Si IV absorption features and the variability of the shapes of the P Cygni profiles of Si I…
Gas release from ice/dust mixtures
Krankowsky, D.; Mauersberger, K.; Hesselbarth, P. +4 more
Gas fluxes from insolated ice/dust mixtures were measured by pressure gauges and a mass spectrometer placed one meter in front of the sample. As soon as the insolation of about one solar constant was started a fast rise in H2O and CO2 emissions from the fresh surface was observed. Thereafter gas fluxes slowly decreased. When …
Life at the Edge: Emission From the H II Region/Photodissociation Region Interface
Hester, J. J.
Preliminary results of an imaging survey of Galactic H II regions are presented and discussed with respect to the character of low-ionization potential lines and the structure of the H II region/photodissociation region (PDR) interface. A model of (S II) emission is developed according to the preliminary results and the interpretation of the struc…
High resolution observations of chromospheric lines in late-type dwarfs.
Houdebine, E. R.; Byrne, P. B.; Panagi, P. M.
High resolution H-alpha absorption- and emission-line profiles are reported for 11 stars of spectral types ranging from K5V to M3V, and the profiles of NaI(D), HeI(5876A), and CaII(IR) are given for portions of the sample. The observations were taken with the Qubes spectrograph, and the data are reduced by comparing the spectral data with observat…