Search Publications
Is V426 Ophiuchi really an intermediate polar ?
Hellier, Coel; O'Donoghue, Darragh; Buckley, David +1 more
The dwarf nova V426 Oph has been proposed as an intermediate polar with a report of a 60-min period in the X-ray band. Optical photometry and spectroscopy show no evidence for such a period. Additionally, reanalysis of the X-ray data shows that the 60-min period is not significant and that the variability is consistent with flickering. Overall, no…
IUE observations of mass-loss spectral features in B5-B9 supergiants.
Bates, B.; Gilheany, S.
A survey of IUE spectra is presented for supergiants of spectral class B5-B9 illustrating the behavior of line profiles associated with mass-loss effects. The main purpose of this survey is to better identify the spectral mass-loss features which occur in such stars in order to present a clearer observational picture of the nature and the timescal…
Effective temperatures of RCB stars.
Evans, A.; Bode, M. F.; Albinson, J. S. +1 more
IUE observations and optical-IR photometry are reported for a number of R Coronae Borealis stars, including the LMC object W Men. Non-line-blanketed, hydrogen-deficient model atmospheres are normalized to the data in the IR to determine effective and color temperatures. By comparing stellar flux distributions with model atmosphere calculations, wa…
Self-consistent comptonized models for the spectra of low-mass X-ray binaries.
Ross, R. R.; Ponman, T. J.; Foster, A. J.
We have constructed Comptonized spectral models and fitted them to EXOSAT spectra of eleven bright low-mass X-ray binaries. The models are based on the premise that these systems contain circumstellar material which modifies the X-ray spectrum passing through it. We idealize this situation as a point source of X-rays, the neutron star, embedded in…
Fe - MG II K line fluorescence in K giant and bright giant stars.
Harper, G. M.
Emission lines of Fe I from the multiplet uv44 are observed at 2823.28A and 2843.98A in late-type giant and bright giant stars. It has been recognized for some time that these lines can be excited by Mg II k line radiation in the transition at 2795.54A. The first radiative transfer calculations to account for the strength of the Fe I lines Iota Au…
X-ray observations of the radio galaxy Pictor A.
Singh, K. P.; Rao, A. R.; Vahia, M. N.
strong X-ray emission is detected from the active nucleus of an emission- line radio galaxy Pictor A, during observations with the EXOSAT observatory. The nuclear X-ray emission is observed to be steady on time- scales of a few minutes to a few hours. The X-ray spectrum is adequately explained by a simple power law with the photon index {GAMMA} = …
An X-ray flare on the short-period, eclipsing binary UMa.
Jeffries, R. D.; Bedford, D. K.
An EXOSAT observation of a flare on the short-period, eclipsing RS CVn binary system XY UMa is reported. The light curve is interpreted within the framework of cooling plasma within loop-like magnetic structures, and limits on the flaring plasma and magnetic field parameters are derived using the light curve decay time and flare emission measure. …
The photospheric temperatures and composition of very hot He-rich white dwarfs.
Barstow, M. A.; Holberg, J. B.
Results are reported from a detailed analysis of Exosat observations of six hot He-rich white dwarfs belonging to, or related to, the spectroscopic subclass of PG1159 stars. These objects are thought to evolve directly from O VI type planetary nebulae nuclei and provide an important link in models of white dwarf evolution. When the Exosat data are…
The Changing Soft X-Ray Lightcurve of the Am-Herculis System Mr-Serpentis = PG:1550+191
Stella, L.; Osborne, J. P.; Angelini, L.
We report the first soft X-ray light curves of the AM Her system MR Ser, all obtained within a 4-month interval in 1984. The source was serendipitously detected on three occasions by the EXOSA T low-energy telescope, and one observation was made in which MR Ser was the target. MR Ser was probably in a high optical state throughout, although it was…
The long-period binary UU CANCRI as a system that has reversed its mass ratio.
Eaton, J. A.
UU Cnc is a 96-d binary system (K4 111+?) which has been interpreted as a contact binary, presumably representing the common-envelope stage of evolution. Since this is such a bizarre possibility, we have tested it by using the rotational velocity to determine the mass ratio and by obtaining lUE observations to search for the hot, accreting source …