Search Publications
The beta Pictoris circumstellar disk. VI. Evidence for material falling on to the star.
Ferlet, R.; Vidal-Madjar, A.; Lagrange-Henri, A. M.
New archive observations with International Ultraviolet Explorer are used to study the temporal variations of the circumstellar absorption towards β Pictoris. The authors first show that strong variations occur in the redshifted part of the resonance lines of Al III, Mg II, and Fe II, and also of metastable lines of Fe II. These variations are the…
Relative C, N, O abundances in red giants, planetary nebulae, novae and symbiotic stars.
Vogel, M.; Nussbaumer, H.; Schild, H. +1 more
C/N and O/N abundance ratios deduced from UV data are presented for 24 symbiotic stars. There is little scatter in these ratios, indicating that the symbiotic phenomenon only occurs in a well defined evolutionary stage. Comparison with related objects such as red giants, novae, and planetary nebulae reveals that symbiotic objects best fit the CNO …
A non-LTE stellar atmosphere study of nitrogen-rich early-type stars.
Butler, K.; Kudritzki, R. P.; Herrero, A. +4 more
Spectrograms of a sample of nitrogen-rich early type stars (OBN stars) are analyzed differentially to normal stars of similar spectral types by means of NLTE methods. Effective temperatures, gravities and atmospheric helium contents are derived by fitting theoretical profiles of hydrogen and helium lines to the observations. The abundance analysis…
Ultraviolet observations of AM Her.
Heise, J.; Verbunt, F.
Observations of AM Her at different flux levels obtained with IUE are presented. From the observations obtained at the lowest flux level, an upper limit to the white dwarf temperature of about 20,000 K, is derived, confirming an earlier temperature determination by Schmidt et al. (1981) from optical spectrophotometry. The increased flux levels at …
The chemical composition of the lambda Bootis stars.
Baschek, B.; Slettebak, A.
Measurements of the equivalent widhts of 24 UV lines from IUE spectra of 10 λ Bootis or suspected λ Bootis stars and 19 normal standard stars of spectral types B8-A7 are compared with line strengths calculated from model atmospheres. The light elements (C, N, and O) in the λ Boo stars are in the range slightly overabundant relative to the standard…
Rotational modulation and flares on RS CVn and BY DRA stars. IX. IUE spectroscopy and photometry of II Peg and V711 Tau during February 1983.
Linsky, J. L.; Catalano, S.; Rodono, M. +11 more
Evidence is presented for spots, plages, and flares on the noneclipsing RS CVn system II Peg and V 711 Tau. The large spot originally found on II Peg in 1981.8 could still be identified in 1983. Two spectroscopic flares of II Peg were detected. For the larger flare the fluxes in the strongest transition-region lines reached about six times their q…
IUE low resolution observations of the symbiotic star CH Cygni in 1979-1986.
Hack, M.; Mikolajewska, J.; Selvelli, P. L.
Data from IUE observations of the semiregular variable CH Cyg are presented compiled in extensive tables and graphs and analyzed with reference to theoretical models. The UV/optical continuum emission is accounted for by combining a Kurucz (1979) low-gravity A-type model atmosphere at Te = 8500-9000 K with hydrogen bound-free + free-free emission …
The optical and UV spectrum of the Seyfert type 2 galaxy NGC 3393.
Prieto, M. A.; Wamsteker, W.; Diaz, A. I.
The combined UV and optical spectrum of the Seyfert type 2 galaxy NGC 3393 is presented and analyzed together with published IR and IRAS data. The conditions in the narrow line gas strongly suggest that the high ionization material is in a zone of higher density (N_e_=10^5^ cm^-3^) while the low ionization material is at N_e_=10^3^ cm^-3^. No evid…
4 Draconis : a unique triple system containing an M3 giant and a cataclysmic binary.
Reimers, D.; Brown, A.; Griffin, R. F.
The M3 III giant 4 Dra has a UV bright companion discovered with IUE as a probable cataclysmic variable (CV). The authors determine the orbit of the M giant around the centre of gravity of the system that it forms with the cataclysmic binary and find P = 1703 d, e = 0.30, a1msin i = 82 Gm, and f(m) = 0.0076 M_sun;. They find that 4 Dra …
High-resolution spectroscopy of central stars of planetary nebulae : LSS 1362.
Werner, K.; Heber, U.; Drilling, J. S.
High resolution spectra of the hot sdO star LSS 1362, a central star of a planetary nebula, are analyzed by means of model atmosphere techniques. Improved NLTE model atmospheres based on the newly developed 'accelerated lambda iteration' method are used. The very high effective temperature (100000 K) derived previously from the UV energy distribut…