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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…
The spectrum of the planetary nebula IC 351
Feibelman, Walter A.; Hyung, Siek; Aller, Lawrence H.
International Ultraviolet Explorer (IUE) and optical region spectroscopic observations are presented for the moderately high-excitation planetary nebula IC 351. Most of the atoms are distributed over a narrow range of ionization. Thus [NII] and [SII] are weak; [NeIV] is prominent, but [NeV] is missing. It appears that the metal/hydrogen ratio is s…
The ultraviolet polarization of the Crab pulsar
Lyne, A. G.; Dolan, J. F.; Boyd, P. T. +3 more
The linear polarization of the Crab pulsar has been observed in the ultraviolet using the High Speed Photometer on the Hubble Space Telescope. The polarization as a function of pulse phase is strikingly similar to that observed in the visible, with the same values of fractional polarization and the same swing of position angle occurring through th…
The extreme-ultraviolet spectrum of the central star of the planetary nebula NGC 1360
Dreizler, Stefan; Drake, Jeremy J.; Werner, Klaus +1 more
We have used the Extreme Ultraviolet Explorer (EUVE) to obtain the first EUV spectrum of the central star of a planetary nebula, that of NGC 1360. The photospheric spectrum shows continuum absorption edges due to O^4+ as well as absorption-line features. NLTE model atmospheres including line blanketing by iron-group elements can match the general …
The variable mass loss of the peculiar supergiant P Cygni.
Sterken, C.; Israelian, G.; Parker, J. W. +1 more
The study of iron lines from 49 high-resolution IUE spectra observed in the period of 1985-1991 allowed us to find a repetition time between two successive shells of the order of six months. We found that absorption lines of Fe III often have two components while Fe II lines can have three. P Cygni is the only luminous blue variable that does not …
Non-LTE model chromospheres of zeta Aurigae stars
Marshall, K. P.
Plane-parallel, one-component, non-local thermodynamic equilibrium (LTE), semi-empirical model chromospheres have been constructed for the primary stars in the zeta Aurigae systems HR 6902 and 22 Vul. This has been accomplished by means of radiative transfer calculations undertaken with a non-LTE multilevel radiative transfer code, MULTI, and curv…