Search Publications
The 1986FEB Solar Activity - a Comparison of Giotto VEGA-1 and IMP-8 Soalr Wind Measurements with Magnetohydrodynamic Simulations
Coates, A. J.; Dryer, M.; Johnstone, A. D. +1 more
Large disturbances in the interplanetary medium were observed by several spacecraft during a period of enhanced solar activity in early February 1986. The locations of six solar flares and the spacecraft considered here encompassed more than 100° of heliolongitude. These flares during the minimum of cycle 21 set the stage for an extensive multi-sp…
Photometric and spectroscopic studies of cool stars discovered in EXOSAT X-ray images. I. Time variability and spectral classification of eight southern stars.
Tagliaferri, G.; Pasquini, L.; Pallavicini, R. +4 more
As part of a larger program to study the optical properties of serendipitous Exosat sources, optical photometry and low-resolution spectroscopy are presented for eight southern stars which have been identified as optical counterparts of Exosat sources. X-ray flux variability has been detected for three of them. In all three cases the optical count…
The UV variability of the intermediate polars TW Pictoris (H 0534-581) and TX Columbae (1H 0542-407).
Bonnet-Bidaud, J. M.; Buckley, D. A. H.; Mouchet, M. +1 more
UV observations of two X-ray sources suggested to be nonsynchronous magnetic cataclysmic binaries (TW Pic and TX Col) are reported. Each source was observed at different epochs with simultaneous optical photometry in one case (TW Pic). The UV spectrum of both sources is typical of intermediate polars, showing a blue continuum with strong N V, C IV…
The SI II intercombination multiplet in late-type stars.
Dufton, P. L.; Keenan, F. P.; Byrne, P. B. +3 more
New atomic data are used to calculate the relative intensities of transitions within the Si II 3s(2)3p(2)P-3s3p(2) 4P intercombination multiplet for plasma parameters appropriate to late-type stellar atmospheres. These ratios are found to be significantly different from those of Dufton and Kingston, (1991), principally due to changes in the radiat…
A Study of the Young Massive Cluster N90 in the SMC
Thompson, I. B.; Hutchings, J. B.; Cartledge, S. +1 more
We present optical and UV spectra of O and B stars in the compact nebulous cluster Henize N90 in the SMC. The brightest stars are of type O and B, although our optical and UV classifications do not all agree closely. We discuss the spectra, effective temperatures, bolometric luminosities, extinction, stellar winds, and the evolutionary state of th…
Quasi-periodic oscillations in short type II bursts from the Rapid Burster.
Stella, L.; van Paradijs, J.; van der Klis, M. +4 more
The authors present and discuss new information on quasi-periodic oscillations (QPO) in type II bursts from the Rapid Burster, which are under 30 sec in duration.
EXOSAT observations of the X-ray burst source 4U 1702-42.
van Paradijs, J.; van der Klis, M.; Lewin, W. H. G. +2 more
The two Exosat observations of 4U 1702 - 42 are reported. In one of them three bursts are detected. The bursts and the spectral and fast-temporal behavior of the persistent emission are analyzed. It is concluded that 4U 1702 - 42 is an atoll source, which was in the banana state when the bursts were present. The characteristics of the burst are si…
The nature of the F STR lambda 4077 stars. IV. Search for white dwarfs around barium dwarfs.
Lanz, T.; North, P.
The energy distribution of three stars classified as F str 4077-A by Bidelman has been observed in the ultraviolet with the IUE satellite. Although the stars examined have the same kind of abundance anomalies as the Ba giants and Bond's CH subgiants (i.e. an overabundance of s-process elements), no UV excess related with the presence of the expect…
The Ultraviolet Spectrum of Scorpius X-1 as Observed by IUE: 1978--1988
Raymond, J. C.; Kallman, T. R.; Vrtilek, S. D.
The IUE observations of Sco X-1 taken prior to September 1988 are summarized. These data are tested for variability associated with orbital motion and for correlations between the various observables. The continuum spectra are fitted to simple models for accretion disk atmospheres which demonstrate that X-ray heating dominates the outer regions of…
Spectral transformation of the unusual variable star MWC560 to resemble a nova
Sonneborn, George; Maran, Stephen P.; Oliversen, Ronald J. +1 more
MWC560 is an emission-line star catalogued1in 1943 and later described2 as an 'extraordinary symbiotic-like variable'. It was recently found3 to be undergoing a photometric and spectroscopic outburst. A dramatic change has occurred in the ultraviolet spec-trum of MWC560, so that it now closely resembles the spectru…