Search Publications
The radial brightness dependence in the dust coma of comet P/Grigg-Skjellerup.
Fulle, M.; Mennella, V.; Colangeli, L. +2 more
In a previous paper (Fulle et al. 1993a) we have obtained a three-dimensional coma model of the short period comet P/Grigg-Skjellerup, by fitting ground-based images taken in coincidence with the fly-by of the GIOTTO spacecraft (GEM mission). Concerning the cometary dust environment, we confirmed the excess of large grains measured by the in-situ …
The helium-to-hydrogen ratio of the UV-bright star Barnard 29 of Messier 13.
Adelman, S. J.; Sweigart, A. V.; Aikman, G. C. L. +2 more
Barnard 29 is the most luminous UV-bright star of the globular cluster Messier 13. Comparison of its reddening corrected optical region spectrophotometry and IUE low dispersion fluxes and its H-gamma profile with the predictions of metal-poor model atmospheres having the metallicity of M 13 indicated Teff = 20250 K, log g = 3.15. Observ…
Hot stars near the position of X0512-401 in the globular cluster NGC 1851.
Bonnet-Bidaud, J. M.; Koch-Miramond, L.; Auriere, M.
We have conducted an investigation of the error box of the X-ray source in NGC 1851 in the optical (ESO, La Silla) and ultraviolet (IUE) ranges. The central field of NGC 1851 was observed in UBV CCD photometry. Two IUE observations, with different slit orientations were used (one from archives, one obtained for this study). The optical photometry …
Particle acceleration by an interplanetary shock-pair seen at ULYSSES at 3.15 AU.
Tappin, S. J.; Lanzerotti, L. J.; Roelof, E. C.
Observations from the HI-SCALE instrument on Ulysses of the ions and electrons associated with an interplanetary shock-pair at about 3.15 AU are presented. An empirical model is used to derive the evolution of the particle distribution in the solar wind frame. The forward shock is shown to be the primary source of ion acceleration, while the weake…
Multiwavelength observations of RV Tauri stars II. U Monocerotis
Evans, A.; Marang, F.; Shenton, M. +3 more
We present ultraviolet spectroscopy, and optical and infrared photometry, of the RV variable U Mon. The MgII emission in this object seems to be chromospheric, with small variations in profile accompanying pulsational variations. The wavelengths of narrow absorption features associated with the MgII emission are essentially constant in time, and s…
Observations and analyses of the S VI λ1975, λ1993A lines in the IUE ultraviolet spectra of WN stars.
Willis, A. J.; Nugis, T.
From a detailed study of high resolution IUE ultraviolet spectra we identify strong emission lines near ~λ1990A as the S VI (4p^2^P^0^-4d^2^D) transitions at λ1975.21A, λ1992.56, 1993.24A in HD 187282 (WN4), HD 50896 (WN5), HD 191765 (WN6) and HD 192163 (WN6). These S VI emissions may also be weakly present in HD 151932 (WN7). Additional S VI (4s …
β1 Monocerotis: oscillations and chromospheric structure
Ringuelet, A. E.; Colombo, E.; Maranon di Leo, C.
β1 Monocerotis is a Be star with a V/R cycle of 12.5 years. We observed the star from CTIO (Chile) and with the IUE satellite and found that the star undergoes photospheric oscillations of 1.7 hours and presents a chromospheric structure in the extended atmosphere. Infall velocities and ejection of material are discussed.
The exciting star of the small bubble N 120A in the Large Magellanic Cloud
Gry, C.; Rosado, M.; Marcelin, M. +2 more
UV characteristics of the star BI 141 show that it is the exciting star of the nebula N 120A of the LMC. We determine its UV spectral classification as O_9.5_I and we derive the terminal velocity and mass-loss rate of its stellar wind, in agreement with the usual values found for galactic supergiants of the same spectral type. The energetic balanc…
The Chemical Evolution of the Galactic Disk - Part One - Analysis and Results
Gustafsson, B.; Andersen, J.; Lambert, D. L. +3 more
The ultraviolet to soft X-ray bump of Seyfert 1 type active galactic nuclei.
Walter, R.; Fink, H. H.
The soft X-ray (0.1 - 2.4 keV) emission of 58 Seyfert type active galactic nuclei have been studied using the spectra obtained during the ROSAT all sky survey. These spectra are well represented by power law models with photon indices ranging between 1.6 and 3.4. The spectra usually do not show intrinsic absorption. A notable exception is Mrk 766 …