Search Publications
The ionization of the winds from cataclysmic variables without classical boundary layers.
Drew, Janet E.; Hoare, Melvin G.
We have calculated a grid of detailed photoionization models for the stellar winds in non-magnetic cataclysmic variables. In the light of evidence which questions the existence of a classical hot, luminous boundary layer we investigate (i) models with cool, luminous boundary layers or (ii) models with no boundary layer at all, but with a moderatel…
Cosmic-abundance absorption dips in X1755-33.
Church, M. J.; Balucinska-Church, M.
Results of spectral analysis for the source X1755-33 using the 1984 EXOSAT/ME data are presented, with spectral fitting made to the complete 18-h observation by dividing it into 314 consecutive 400-s timebins. It is found that spectral changes take place on time scales of this order and that analysis of longer sections of data can lead to errors. …
The broad-band X-ray spectral variability of MRK 841.
Nandra, K.; Turner, T. J.; Done, C. +3 more
The results of a detailed spectral analysis of four X-ray observations of the luminous Seyfert 1.5 galaxy Mrk 841, performed using the EXOSAT and Ginga satellites over the period 1984 June to 1990 July, are reported. Preliminary results from a short ROSAT PSPC observation of Mrk 841 in 1990 July are also presented. Variability is apparent in both …
AGN X-ray light curves - shot noise or low-dimensional attractor ?
McHardy, Ian M.; Czerny, Bozena; Lehto, Harry J.
We use correlation integrals to determine whether the X-ray variability of AGN, as seen in EXOSAT observations, arises from chaotic systems. We distinguish three characteristic types of behaviour. We also analyse a number of simulated light curves, to investigate the poorly understood limitations to the correlation integral method caused by noise …
The extended nebulosity in the radio galaxy 3C 227.
Walsh, J. R.; Prieto, M. A.; di Serego Alighieri, S. +1 more
3C 227 (z = 0.085) exhibits one of the more spectacular extended nebulosities to be found among active galaxies at moderate redshifts. The gas can be traced to radial distances of about 100 kpc (H_0_ = 50 km s^-1^ Mpc^-1^). The total [O III] 5007-A luminosity is 2.7 X 10^42^ erg s^-1^, of which at least 50 per cent is radiated from the extended re…
Improved effective temperatures for hydrogen-deficient binary stars.
Jeffery, C. S.; Dudley, R. E.
Effective temperatures are obtained for all four known hydrogen-deficient binary stars, using published and archival photometry and new line-blanketed model atmospheres. These model atmospheres largely resolve the well-known mismatch between the theoretical and observed flux distribution for Upsilon Sgr, although a discrepancy persists at short wa…
ROSAT/IUE discovery of a white dwarf companion to HD 33959C.
Barstow, M. A.; Hodgkin, S. T.; Pye, J. P. +2 more
We report the discovery, from the ROSAT EUV and X-ray all-sky surveys, and from IUE spectra, of a white dwarf (WD) companion to HD 33959C. RE 0515 + 324 is among the 10 brightest EUV sources in the sky in the 100-200 A band. It is also a strong soft X-ray source. IUE observations of candidate objects have revealed a previously uncataloged hot DA W…
The chemical compositions of Algol systems - V. Confirmation of carbon deficiencies in the primaries of eight systems.
Lambert, D. L.; Lemke, M.; Tomkin, J.
We use low-noise CCD spectra of 4267-Å C II line in the spectra of eight Algol-type eclipsing binaries to measure the C abundances of their primaries. A differential LTE analysis of the Algol binaries with respect to single standard stars of the same spectral type shows marginal to moderate deficiencies of C in the primaries of the binaries. We fi…
Optical and ultraviolet observations of the star LkHα 264.
Collier Cameron, A.; Gameiro, J. F.; Lagor, M. T. V. +1 more
We present new ultraviolet and optical data for the classical T Tauri star LkH-alpha 264. The most important features in the UV spectrum are identified and their fluxes are measured. These fluxes are then compared to the corresponding values in the sun and in other T Tauri stars. Our time series of high-resolution spectra for the regions of the H-…
High-velocity spectra features in V854 Centauri : evidence for dust formation ?
Lawson, W. A.; Whitney, B. A.; Clayton, G. C. +1 more
Low-dispersion lUE spectra of V854 Cen show apparent shifts or splitting in the λ2325 C II], λ2800 Mg II, λ2851 Mg I and λ2965 C I lines which, if kinematic, indicate velocities in excess of 1000 km s-1. The variations are seen in all the UV emission lines simultaneously. The line splitting seems to occur at times near phase 0.0 (maximu…