Search Publications
Two patterns of correlated X-ray timing and spectral behaviour in low-mass X-ray binaries.
van der Klis, M.; Hasinger, G.
Exosat data are used to study the power spectra of 16 LMXBs as a function of their behavior in X-ray color-color diagrams. The study confirms the existence of a class of sources with three-branched Z-shaped colour-colour diagrams characterized by a temporal behavior that is strongly dependent on the position of the source on the Z. Evidence for an…
Accretion-powered X-ray pulsars.
Nagase, Fumiaki
This paper gives an overview of X-ray pulsars powered by the accretion of matter from a companion star in a close binary system. Recent advances in studies of X-ray pulsars are reviewed, with a special focus on the results of observations by the Hakucho and Tenma satellites. Some topics revealed by the Ginga satellite in the last one-and-a-half ye…
The EXOSAT spectral survey of AGN.
Turner, T. J.; Pounds, K. A.
Results are presented from EXOSAT Observations of 48 hard X-ray selected Seyfert type active galactic nuclei (AGN). These include all 30 of the emission line AGN in the Piccinotti sample. Combining EXOSAT LE and ME data has allowed us to obtain X-ray spectra over the broad energy range 0.1 - 10 keV spectra in the ~2-10 keV range are found to be we…
The Stellar Winds of 203 Galactic O Stars: A Quantitative Ultraviolet Survey
Howarth, Ian D.; Prinja, Raman K.
Measurements of the resonance lines of C IV, N V, and Si IV in a sample of 203 O stars observed using IUE in a high-resolution mode are presented. The data are discussed using a consistent set of radius, luminosity, and mass estimates. The ratio of the maximum observed velocity and the terminal (farfield) velocity is found to average at 3.0 for 13…
Fitting Improved Accretion Disk Models to the Multiwavelength Continua of Quasars and Active Galactic Nuclei
Malkan, Matthew A.; Sun, Wei-Hsin
We present fits to the ultraviolet-optical-infrared spectra of 60 quasars and active galactic nuclei (AGNs) using improved black hole accretion disk models. The disk is assumed geometrically thin and optically thick. We included the relativistic effects of disk inclination, including Doppler boosting, gravitational focusing, and gravitational reds…
Kinematic Evidence for a Relativistic Keplerian Disk: ARP 102B
Filippenko, Alexei V.; Halpern, Jules P.; Chen, Kaiyou
The broad emission lines of the elliptical galaxy Arp 102B have peaks which are significantly displaced in velocity with respect to the host galaxy of the active galactic nucleus (AGN). We calculated line profiles for a Keplerian disk, including relativistic effects which were not treated rigorously in previous papers. We found an excellent fit of…
Detection of H3+ on Jupiter
Atreya, S. K.; Drossart, P.; Clarke, J. T. +9 more
SINCE their detection in the high latitudes of Jupiter, first by the Voyager Ultraviolet Spectrometer (UVS) experiment1,2, then by the International Ultraviolet Explorer (IDE) satellite3, the auroral particle precipitations have been associated with various phenomena in the jovian environment. In the magnetosphere, the H…
Hot Dust on the Outskirts of the Broad-Line Region in Fairall 9
Glass, I. S.; Clavel, J.; Wamsteker, W.
Since 1978, the Seyfert 1 galaxy F9 has been observed 54 times in the far-ultraviolet and optical (FES) range with the IUE, and at 27 different epochs at J, H, K, and L. The UV continuum underwent dramatic variations, its intensity decreasing by a factor 33, from a maximum in 1978 to a deep minimum in mid-1984. The near-IR and optical fluxes chang…
Narrow Ultraviolet Emission Lines from SN 1987A: Evidence for CNO Processing in the Progenitor
Panagia, N.; Fransson, C.; Kirshner, R. P. +4 more
UV observations of SN 1987A with the IUE satellite are reported. Spectra after 1987 May 24 show emission lines of He II, C III, N III, N IV, N V, and O III, increasing in strength with time. High-resolution observations show that the widths of the lines are less than ~30 km s^-1^ (FWHM). The line strengths and widths indicate an origin in a photoi…
The Evolution of Chromospheric Activity of Cool Giant and Subgiant Stars
Drake, Stephen A.; Simon, Theodore
IUE spectra for a large sample of cool subgiant stars are examined, and evidence is found that subgiants in the mass range 1.2-1.6 solar masses undergo a sudden decline in UV transition region emission near B - V = 0.6, which corresponds to spectral type G0 IV. The decline in UV emission coincides with a sharp decrease in stellar rotation rates, a…