Search Publications
A spectrophotometric study of the emission lines in the quiescent dwarf nova Z Chamaeleontis.
Horne, Keith; Marsh, T. R.; Shipman, H. L.
The main goal of the present time-resolved spectrophotometric study of Z Cha is to examine the behaviour of the emission lines during the eclipse of the disc by the secondary star. The observations and data reduction techniques are presented first. Then, the white dwarf spectrum is examined, which produces broad absorption wings around the Balmer …
Nova Aquilae 1982.
Snijders, M. A. J.; Seaton, M. J.; Blades, J. C. +4 more
Observations of Nova Aquilae obtained from the IUE, the Anglo-Australian Telescope, and the Westerbork Synthesis Radio Telescope are discussed. Light curves for B, V, and continuum fluxes at 2800 and 1300 A are presented. Velocities obtained from line profiles indicate the presence of three main gaseous components: a high velocity gas (HVG) compon…
X-ray observations of the Ophiuchus, PKS 0745-191 and Cygnus-A clusters of galaxies.
Fabian, A. C.; Mushotzky, R. F.; Nulsen, P. E. J. +4 more
The authors report observations of the X-ray emission from three bright clusters of galaxies at low Galactic latitudes; the Ophiuchus, PKS 0745-191 and Cygnus-A clusters. Temperatures and iron abundances are determined from EXOSAT spectral data. Images of the Ophiuchus cluster show it to have a high central density and a cooling flow. The authors …
Discovery of a strong soft X-ray excess in MKN 335 - evidence for an accretion disc ?
Turner, T. J.; King, A. R.; Pounds, K. A. +2 more
Exosat observations of Mkn 335 reveal a hard power-law spectrum above about 1 keV, typical for Seyfert 1 galaxies, but with unusually strong variability on time-scales of about 1-2 hr. In addition, an intense soft X-ray component is found to dominate the overall spectrum of Mkn 335 below about 0.6 keV. Both soft and hard components increased in st…
Multiwavelength monitoring of the dwarf nova VW Hydri. I. Overview.
van Paradijs, J.; Heise, J.; Verbunt, F. +7 more
Observations from different wavelength regions are used to investigate outburst mechanisms in VW Hydri. Previous observational data on VW Hydri and the present theoretical understanding of dwarf novae are first reviewed. Observational data from the current data set on ordinary outbursts are found to be self-consistently interpreted both by assumin…
Multiwavelength monitoring of the dwarf nova VW Hydri. III. IUE observations.
Verbunt, F.; Pringle, J. E.; Hassall, B. J. M. +2 more
IUE observations of VW Hyi were obtained between September and November 1984 during three ordinary outbursts, one superoutburst, and quiescence. Progressive fall in UV fluxes is noted during quiescence, and the UV flux lags behind the optical flux during the rise to outburst peak. Initially in the superoutburst, the fluxes rise to the level of an …
Multiwavelength monitoring of the dwarf nova VW Hydri. V. EXOSAT observations.
Heise, J.; van der Woerd, H.
Exosat X-ray observations of VW Hyi during three normal outbursts and one superoutburst were obtained in 1984. The decrease in X-ray flux by a factor of 1.2-1.6 during the quiescent periods between outbursts implies that the accretion rate onto the white dwarf decreases by about the same factor, consistent with emission from an optically thin hot …
The carbon-poor halo planetary nebula DDDM-1.
Clegg, R. E. S.; Torres-Peimbert, S.; Peimbert, M.
The authors have analysed ultraviolet and optical spectra of DDDM-1, a planetary nebula in the galactic halo. Abundances of N, O, S, Ne and Ar are all about a factor 6 lower than solar, while Fe and Mg are deficient by a further factor of 3. No carbon lines were seen in any spectra, and the authors obtain the upper limit C/H < 1.4×10-5
High-frequency oscillations from CIR X-1.
Tennant, A. F.
The author reports results from an EXOSAT observation of Cir X-1 during which strong, low-frequency (5-20 Hz) quasi-periodic oscillations (QPO) were detected. QPO were also detected at much higher frequencies (100-200 Hz). These high frequencies are consistent with rotation periods in the inner accretion disc region. High-frequency QPO lend weight…
Constraints on the mass-radius relation of the neutron star in 4U 1746-37/NGC 6441.
van Paradijs, J.; Lewin, W. H. G.; Vacca, W. D. +4 more
An analysis of 12 hours of continuous EXOSAT observations of 4U 1746-37 in NGC 6441, obtained between September 9 and 10, 1985, puts constraints on its mass-radius relation. The spectral shape of the persistent X-ray flux is well fitted by a thermal bremsstrahlung spectrum, with a kT temperature varying between 7.5 and 9.8 keV, and an interstellar…