Search Publications
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…
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.
IUE observations of the quasar 3C263 constrain the ionizing photon luminosity of decaying dark matter.
Fabian, A. C.; Naylor, T.; Sciama, D. W.
Dark matter which produces hydrogen-ionizing photons on a time-scale of 2x1023s has been shown by Sciama to explain many problems in astronomy and cosmology. Clusters of galaxies composed of such dark matter will be luminous sources of ionizing photons. The authors report here the results of a search for an otherwise unidentified, exten…
Ultraviolet observations of the long-period dwarf nova DX And in outburst.
Woods, J. A.; Drew, J. E.; Hoare, M. G.
Ultraviolet observations of the little-studied dwarf nova, DX And, are presented. The observations were made with the International Ultraviolet Explorer satellite during the late stages of a rise to outburst maximum in November 1989. The spectra indicate a low orbital inclination angle and show clear signs of substantial interstellar reddening. Th…
Ultraviolet emission-line variability in 3C273.
Harries, T. J.; O'Brien, P. T.
Evidence is presented for correlated variability between the ultraviolet continuum and the Lyα emission line in the luminous quasar 3C273. Using IUE data covering a period of ~ 1000 d, Lyα varied by 15 per cent whilst the continuum varied by a factor of 2. A time series analysis gives a lag for Lyα relative to the ultraviolet continuum of 74 +/- 3…
On the magnetic energy density in the X-ray emission of active galactic nuclei.
Ghisellini, G.; Fabian, A. C.; Celotti, A.
We estimate upper limits on the magnetic energy density in the compact X-ray emission region of the Seyfert galaxies NGC 4051 and NGC 6814 and the quasars 3C273, 3C279 and H1821 + 643 using synchrotron self-Compton theory. The size of the emission region is obtained from the X-ray variability time-scale, and the electron density from the assumptio…
The variable broad emission line spectrum of 4C 37.43.
Gondhalekar, P. M.; O'Brien, P. T.
The results of a short campaign to monitor the quasar 4C37.43 using the International Ultraviolet Explorer (IUE) satellite are presented. Combining these data with archive data we find clear evidence for ultraviolet continuum and Ly α emission line variability. Most of the Ly α variability occurs in the wings of the line. The C IV λ1549 line may v…
The nearby interstellar material in the general direction towards M 22.
Bates, B.; Gilheany, S.; Wood, K. D.
High-resolution optical spectra of interstellar absorption lines are used to examine reddening variations across the globular cluster M22 which are produced by the nearby low-velocity gas. Fifteen cluster stars together with three stars within 1.3 deg of the cluster were observed in the Na D lines and in some case also the K I (7699 A) line. Optic…
Implications of the ionizing continuum of 3C 263.
Fabian, A. C.; Naylor, T.; George, I. M. +1 more
We present ultraviolet IUE and soft X-ray EXOSAT observations of the quasar 3C 263 which reveal the low-energy part of the ionizing continuum and allow the high-energy tail to be strongly constrained. The ionizing spectrum confirms that the pressure of the extra-nuclear emission-line gas discovered earlier by us around the quasar is greater than 1…
Time-resolved ultraviolet spectroscopy of the cataclysmic variable PG 1711+336.
Prinja, R. K.; Rosen, S. R.; Supelli, K.
Low-resolution IUE ultraviolet observations of the cataclysmic variable, PG 1711 + 336, are presented. The spectra reveal extensive variability in the wind-formed C IV 1550 A resonance line P Cygni profiles, on time-scales as short as several hours. The high-resolution IUE spectrum of the nova-like system V3885 Sgr, convolved with the IUE low-reso…