Search Publications
The chemical composition and binarity of beta Crateris
Stickland, D. J.; Kellett, B. J.; Smalley, B. +1 more
A detailed abundance analysis of the bright A-type star betaCrt is presented. It is found that most of the abundances are essentially solar, indicating that the star is not a hot Am star. The only prominent anomalies are an underabundance of Al and overabundances of S, Sr and Ba. The barium overabundance is the most prominent and has important imp…
Spin and beat phenomena in time-resolved Hubble Space Telescope UV spectroscopy of PQ GEM
Watson, M. G.; Mason, K. O.; Howell, S. B. +2 more
Results of the first low-resolution (6 Angstroms), time-resolved Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) observation of the prototypical strong-field intermediate polar system, PQ Gem, are presented. The lambdalambda1150-2600 continuum light curve is dominated by the 13.9-min rotational signature of the white dwarf at all UV w…
Comments on the amplification bias in lens statistics
Hamana, Takashi; Futamase, Toshifumi; Futamase, Kayoko +1 more
Amplification bias selection effects play an important role in lens statistics. We carefully examine the effect of amplification bias on lens statistics taking the following points into account. First, because each lens model has its own amplification bias, it must be estimated self-consistently. Secondly, in general, because the bias depends not …
A survey of vacuum-ultraviolet extinction curves based on International Ultraviolet Explorer spectra
Patriarchi, P.; Megier, A.; Aiello, S. +1 more
This paper presents the interstellar extinction curves derived from the International Ultraviolet Explorer (IUE) spectra with the aid of the already published `artificial standards'. The variety of possible shapes of the curves, demonstrated earlier on spectra from the TD/1 satellite, is fully confirmed.
HST observations of IP Pegasi in quiescence: the pre-eclipse spectrum
Eracleous, Michael; Szkody, Paula; Horne, Keith +5 more
We present time-resolved HST ultraviolet (UV) spectroscopy and ground-based optical photometry of the dwarf nova IP Pegasi in a quiescent state. The observations were obtained prior to an eclipse, when the bright spot caused by the impact of the accretion stream with the edge of the disc dominates the light output. The optical light curve is fairl…
High-redshift galaxies in the Hubble Deep Field: colour selection and star formation history to z~4
Ferguson, Henry C.; Giavalisco, Mauro; Dickinson, Mark E. +3 more
The Lyman decrement associated with the cumulative effect of HI in QSO absorption systems along the line of sight provides a distinctive feature for identifying galaxies at z>~2.5. Colour criteria, which are sensitive to the presence of a Lyman continuum break superposed on an otherwise flat UV spectrum, have been shown, through Keck spectrosco…
Galaxy morphology to I=25 mag in the Hubble Deep Field
Santiago, B. X.; Glazebrook, K.; Abraham, R. G. +3 more
The morphological properties of galaxies in the range 21<<e1>I<</e1>25 mag in the Hubble Deep Field are investigated using a quantitative classification system based on measurements of the central concentration and asymmetry of galaxian light. The class distribution of objects in the Hubble Deep Field is strongly skewed towards h…
The life-cycle of star formation in distant clusters
Smail, I.; Barger, A. J.; Ellis, R. S. +3 more
We analyse the detailed distribution of star-forming and post-starburst members in three distant (z=0.31) galaxy clusters in terms of evolutionary sequences that incorporate secondary bursts of star formation on pre-existing stellar populations. Using the number density of spectroscopically confirmed members of the EW(Hdelta) versus B-R plane from…
Evolution of the aligned structures in z~1 radio galaxies
Best, P. N.; Rottgering, H. J. A.; Longair, M. S.
Hubble Space Telescope observations are presented of eight 3CR radio galaxies in the redshift interval 1<~<e1>z<~</e1>1.3. The optical morphologies of these galaxies change dramatically as the radio size increases. It is shown that this evolution is entirely consistent with large-scale star formation induced by the radio jet, and…
The average X-ray/gamma-ray spectrum of radio-quiet Seyfert 1s
Zdziarski, Andrzej A.; George, Ian M.; Gondek, Dorota +5 more
We have obtained the average 1-500 keV spectrum of radio-quiet Seyfert 1s using data from EXOSAT, Ginga, HEAO-1 and GRO OSSE. The spectral fit to the combined average EXOSAT and OSSE data is fully consistent with that for Ginga and OSSE, confirming results from an earlier Ginga/OSSE sample. The average spectrum is well fitted by a power-law X-ray …