Search Publications
The globular clusters in M87: a bimodal colour distribution
Elson, Rebecca A. W.; Santiago, Basilio X.
We present V and I photometry for ~150 globular clusters with 20<<e1>V<</e1>27 about 2.5 arcmin from the centre of M87, the cD galaxy in the Virgo cluster. The data were acquired with the Hubble Space Telescope which, with an effective resolution of 0.1 arcsec, allows us for the first time to distinguish between globular clusters…
HST photometry of 47 TUC and analysis of the stellar luminosity function in Milky Way clusters
Elson, Rebecca A. W.; Gilmore, Gerard F.; Santiago, Basilio X.
We present V and I photometry for over 1000 stars in a region 5 arcmin from the centre of the globular cluster 47 Tuc. The field was imaged with the Wide Field and Planetary Camera 2 (WFPC-2) as part of the Hubble Space Telescope's Medium Deep Survey key project. The luminosity function (LF) continually rises in the domain 5<~<e1>M_I<~…
Solving the mystery of the heavy-element opacity in the DA white dwarf GD 394.
Barstow, M. A.; Bruhweiler, F. C.; Holberg, J. B. +3 more
The white dwarf GD 394 is one of a very small number of bright hot DAs which have detectable quantities of highly ionized heavy elements in their spectra. Whether this material resides in the photosphere of GD 394 or is in the form of a circumstellar shell has been the subject of much debate, with the large discrepancy between the published radial…
Superhumps and ultraviolet superdips: HST observations of OY Car.
Marsh, T. R.; Horne, K.; Cheng, F. H. +5 more
HST observations of the cataclysmic variable OY Car in superoutburst show dips in its ultraviolet light curve coincident with the optical superhump. By analogy with the light curves of X-ray dippers, the authors believe this to be due to obscuration of the hottest regions of the disc by the vertical structure flaring up at the edge of the disc. Th…
Multifrequency observations of the eclipsing symbiotic triple system CH Cyg during the 1992-94 active phase.
Ivison, R. J.; Davis, R. J.; Chochol, D. +14 more
The authors present UBV photoelectric photometry, plus optical and ultraviolet low- and high-resolution spectroscopy and MERLIN, VLA and JCMT radio/mm-wave observations of the symbiotic star CH Cyg during the period 1989.7-1995.5 which covers the 1992 outburst. On 1990 July 22 the spectrum displayed only absorption features characterized by broad …
Candidate primeval galaxies in the Hubble Deep Field.
Clements, D. L.; Couch, W. J.
The authors present the results of colour selection of candidate high-redshift (2.6 < z < 3.9) galaxies within the Hubble Deep Field based on the Lyman break at 912 Å. The authors find eight such objects in the region, giving a comoving number density comparable to that of nearby bright galaxies (for a flat q0 = 0.5, H0…
Angular sizes and luminosity evolution of faint galaxies
Im, M.; Griffiths, R. E.; Roche, N. +2 more
We investigate the number counts and the V-I colour, angular size and axis ratio distributions of 5384 faint galaxies detected with the refurbished Hubble Space Telescope (HST) Wide Field Planetary Camera, to limits of I~=25 on a 27-field strip and I~=26 on a single deeper field. These results are compared with non-evolving and pure luminosity evo…
Ultraviolet spectroscopy of the hotspot in the classical T Tauri star DI Cep: observational indications of magnetically channelled accretion.
Fernández, M.; Gómez de Castro, A. I.
T Tauri stars (TTS) are low-mass pre-main-sequence stars that are accreting mass from the surrounding disc. The hotspots detected in some of them are probably heated by the release of gravitational energy in the accretion of the disc material on to the star. In this work we study the UV spectrum of the hotspot detected in DI Cep to constrain the p…
Compact radio structure in the Seyfert nucleus of NGC 5929.
Muxlow, T. W. B.; Steffen, W.; Kukula, M. J. +4 more
The authors present MERLIN and VLA radio measurements of the Seyfert galaxy NGC 5929 at 15, 8, 5, 1.6 and 0.4 GHz. All measurements have subarcsecond angular resolution ranging from 0.6 arcsec at 0.4 GHz to 50 mas at 5 GHz. The authors confirm the triple structure reported in earlier studies. The weak central source of the triplet is almost certai…
Nova V351 Puppis 1991: a multiwavelength study of the nebular phase
Sonneborn, G.; Saizar, P.; Shore, S. N. +4 more
We combine ground-based optical and IUE spectrophotometry to study the physical conditions in the shell of Nova V351 Puppis 1991. The structure and the evolution of the shell during the early nebular (i.e. optically thin) phase are discussed in this paper. The reddening, derived from recombination lines, is E(B-V)=0.72+/-0.10. The optical/UV light…