Search Publications
Detection by ISO of the far-infrared OH maser pumping lines in IRC+10420
Barlow, M. J.; Liu, X. -W.; Cox, P. +8 more
The population inversions which lead to circumstellar hydroxyl (OH) maser emission from cool stars have long been thought to be radiatively pumped. However, the proposed pumping mechanism has not been directly observed before now, because the spectral lines that correspond to the rotational transitions of the pumping cycle lie in the far-infrared,…
The neon abundance in WC stars - I. ISO SWS spectroscopy of WR146 (WC6+O)
Crowther, P. A.; Willis, A. J.; Morris, P. W. +4 more
We present infrared spectroscopy in the wavelength range 2.6-20mum of the WC6+O binary system WR146 (MR112) obtained with the Short Wavelength Spectrometer (SWS) on the Infrared Space Observatory (ISO). These data are combined with ground-based optical (INT) and near-IR (UKIRT) spectroscopy and theoretical continuum distributions revealing E(B-V) …
The mass, temperature and distance of the white dwarf in V471 Tauri
Barstow, M. A.; Holberg, J. B.; Cruise, A. M. +1 more
We present an analysis of far-UV observations of V471 Tauri made during the first ORFEUS mission. Combining this spectrum with archival data from IUE allows a first unambiguous measurement of the effective temperature and surface gravity of the white dwarf by matching the observed Lyman line profiles to the predictions of stellar model atmosphere …
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…