Search Publications
A month in the life of NGC 4151: velocity-delay maps of the broad-line region
Horne, Keith; Ulrich, Marie-Helene
We analyse continuum and emission-line variability in NGC 4151 based on IUE spectra taken with nearly complete 1-d sampling over a 35-d interval during 1991 November-December. The 1320-Angstroms continuum undertook a bumpy exponential decline by a factor ~3 over 25 d, and then made a dramatic recovery in ~2d near the end of the campaign. The same …
Optical and ultraviolet spectrophotometry of the ONeMg Nova V838 Herculis 1991
Shore, Steven N.; Sonneborn, George; Wagner, R. Mark +2 more
We present an analysis of optical and UV spectra of the fast nova V838 Herculis 1991. IUE observations began on 1991 March 25 and continued through 1991 August 20, while optical observations began on 1991 March 29 and continued through 1991 August 20. We determine a value for the reddening of E(B-V)~0.5+/-0.1 and a distance of ~3+/-1 kpc based bot…
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…
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 …
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…
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 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…