Search Publications
Non-LTE model atmosphere analysis of the early ultraviolet spectra of Nova OS Andromedae 1986
Sonneborn, G.; Baron, E.; Shore, Steven N. +4 more
We analyse the early, optically thick, ultraviolet spectra of Nova OS And 1986 using a grid of spherically symmetric, non-LTE, line- blanketed, expanding model atmospheres and synthetic spectra with the following set of parameters: 5000<=T_model<=60000K, solar abundan ces, rho ~r^-3, v_max=2000 km s^-1, L=6x10^4Lsolar, and a statistical or m…
The orbit of the supergiant component of VELA X-1 derived from IUE radial velocities
Lloyd, C.; Stickland, D.; Radziun-Woodham, A.
47 short-wavelength, high-resolution IUE spectra have been used to derive the orbital elements of HD 77581, the supergiant companion to the neutron star in the X-ray source Vela X-1; the velocity amplitude is at the lower end of the range found by previous workers using primarily optical spectra, but other elements (e, omega) are in fair agreement…
New, sub-0.1-arcsec radio maps of two young planetary nebulae
Pedlar, A.; Bryce, M.; Thomasson, P. +2 more
Sub-0.1-arcsec maps of the 5-GHz continuum emission from two young planetary nebulae (NGC7027 and BD+303639) have been obtained by combining MERLIN and VLA observations, resulting in the highest spatial resolution radio maps of these (or any) planetary nebulae to date. Small clumps of emission are resolved within the essentially ring-like structur…
A weak lensing survey in the fields of z~1 luminous radio sources
Smail, Ian; Bower, Richard G.
In this paper we present weak lensing observations of the fields around eight z~1 luminous radio sources. These data are used to search for the lensing signatures of mass structures that either are physically associated with the radio objects, or are foreground systems projected along the line of sight. The radio sources were all the subjects of d…
Abundance analysis of the slow nova PW Vulpeculae 1984
Shore, Steven N.; Hauschildt, Peter H.; Schwarz, Greg J. +1 more
We determine the elemental abundances for the ejecta of the slow nova PW Vul 1984. Our technique uses a minimization of the emission-line fits of a photoionization model to available ultraviolet, optical and infrared spectra. We find the following abundances (by number) with respect to solar: He/H=1.0+/-0.4, C/H=7.0^+7_-4, N/H=85^+59_-41 and O/H=6…
Testing the X-ray variability of active galactic nuclei with the non-linear prediction method
Czerny, Bozena; Lehto, Harry J.
The analysis of eight EXOSAT X-ray light curves of six active galactic nuclei by non-linear prediction methods indicates that the observed variability is truly stochastic and is not caused by deterministic chaos. This result favours X-ray emission models with multiple centres of production of hot, possibly relativistic, electrons.
Pre-eclipse dips in the ultraviolet light curves of two eclipsing nova-like cataclysmic variables
Knigge, C.; Mason, K. O.; Drew, J. E.
Observations of the eclipsing nova-like variables UX UMa and RW Tri with the Hubble Space Telescope reveal substantial orbital modulations in their UV light. These modulations have a minimum about a quarter of an orbital cycle before eclipse. The modulation is deeper in RW Tri, which has the higher orbital inclination of the two binaries. The resi…
Measurement of the ^12C/^13C ratio in planetary nebulae
Walsh, J. R.; Clegg, R. E. S.; Storey, P. J. +1 more
The ^12C/^13C isotopic ratio in the ionized gas in three planetary nebulae has been measured using a new method based on transitions caused by hyperfine effects. The C III] multiplet near 1908A has an F=1/2-1/2 transition at 1909.6A that is completely forbidden in ^12C, but allowed as a result of the non-zero nuclear spin of ^13C. The transition p…
The nature of the optical continuum in NGC5128 (CentaurusA)
Storchi-Bergmann, Thaisa; Kinney, Anne L.; Bica, Eduardo +1 more
We present long-slit observations of NGC5128 in the range lambdalambda3200-9800Angstroms, covering the nucleus and dust lane across the east-west direction, up to ~2.2kpc from the nucleus. The reddening-corrected continua and absorption features, when compared with those typical of a bulge stellar population, show that all locations within 1.8kpc …
Angular sizes of the faint blue galaxies
Im, M.; Griffiths, R. E.; Roche, N. +1 more
We investigate the angular sizes, morphologies and B-I colours of the 21≮I≮24 galaxies imaged on 10 Wide Field Planetary Camera fields. The number of galaxies with bluer colours (B-I<2.0) and moderately large angular sizes exceeds non-evolving predictions by a factor of ~2, but is consistent with pure L* evolution (PLE) models. There is also an…