Search Publications
Faint ultraviolet objects in the core of M13: optical counterparts of the low-luminosity X-ray source?
Ferraro, Francesco R.; Paltrinieri, Barbara; Fusi Pecci, Flavio +2 more
The core of the Galactic globular cluster M13 (NGC 6205) has been observed with WFPC2 on the Hubble Space Telescope through visual, blue, and mid- and far-UV filters in a programme devoted to studying the UV population in a sample of Galactic globular clusters. In the UV colour-magnitude diagrams derived from the HST images we have discovered thre…
The discovery of UV oscillations in WZ SGE
Sion, Edward M.; Wood, Janet H.; Cheng, F. H. +2 more
We report the discovery of ~28-s ultraviolet oscillations in the cataclysmic variable WZ Sge. The strength of the oscillations is strongly wavelength-dependent: the oscillation amplitude decreases rapidly from lambda~1500 to ~1250 A. We interpret this decrease as an indication that the spectrum of the oscillations contains a broad Lyalpha absorpti…
Models of optical/UV continuum in AGN: constraints from the NGC 5548 monitoring campaign
Czerny, B.; Loska, Z.
We analyse the data from the International Ultraviolet Explorer (IUE) observational campaign on the Seyfert galaxy NGC 5548 in the context of 10 phenomenological models. On the basis of the optical/UV data, as well as of constraints from the X-ray observations, we can favour one model of the nucleus: an accretion disc with an inner radius cut-off …
Hubble Space Telescope observations of M31 associations
Magnier, Eugene A.; Lewin, Walter H. G.; van Paradijs, Jan +2 more
We have used HST WFPC-2 observations of five fields along the eastern spiral arm regions of M31 to study the stellar populations. We use fits to stellar models to determine extinction individually for the stars in OB associations in these fields. The range of extinction within each cluster is the major constraint on our ability to determine accura…
On the interpretation of the extinction curves of R Coronae Borealis stars
Zubko, V. G.
The available extinction curves for some RCB stars (R CrB, RY Sgr, MV Sgr and V348 Sgr) have been analysed, making use of the method of regularization for solution of ill-posed problems. This approach allows an estimate of dust grain sizes responsible for fadings of RCB stars. A model involving graphite grains is shown to be preferable for the exp…
Timing the eclipse of HD185510
Simon, Theodore; Jeffery, C. Simon
HD185510 (=V1379 Aql) is an eclipsing double-lined RS CVn binary containing a K0 III/IV giant and a hot subluminous companion. An International Ultraviolet Explorer (IUE) ultraviolet light curve has been obtained through the eclipse of the companion with an average time resolution of one measurement every 19min. This was sufficient to resolve all …
3C 254: the alignment effect and unification schemes
Bremer, M. N.
3C 254 is a radio-loud quasar at z=0.734. Optical line and continuum emission from the underlying galaxy is clearly extended and aligned with the radio axis; the object shows the so-called `alignment effect' which is often seen in powerful radio galaxies. This is the clearest case yet of the continuum alignment effect in a radio-loud quasar. The o…
The vertical disc structure of U Geminorum in outburst
Naylor, T.; La Dous, C.
We have obtained phase-resolved UV spectroscopy from the International Ultraviolet Explorer, and V-band CCD photometry of U Gem in outburst. Our data show little or no orbital modulation outside eclipse, in contrast to the X-ray light curves during outburst, which show large dips. We find that a consistent model of the optical, UV and X-ray light …
A multiwavelength study of the starburst galaxy NGC7771
Alonso-Herrero, Almudena; Davies, Richard I.; Ward, Martin J.
We present a multiwavelength study of the interacting starburst galaxy NGC7771, including new optical and ultraviolet spectra and a previously unpublished soft X-ray ROSAT image and spectrum. The far-infrared, radio and X-ray fluxes suggest that a massive burst of star formation is currently in progress, but the small equivalent width of the Balme…
Redshifts of galaxies close to bright QSO lines of sight
Bowen, David V.; Blades, J. Chris; Osmer, Samantha J. +1 more
To expand the known number of low-redshift galaxies lying close to bright (V<17.2) QSO lines of sight, we have identified 24 galaxies within 11 arcmin of nine QSOs which have been observed with the Hubble Space Telescope (HST). Galaxies are found between redshifts of 0.0114 and 0.145 and lie between 39 and 749h^-1kpc from QSO sightlines. Knowin…