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Automated classification of IUE low-dispersion spectra. I. Normal stars.
Ponz, J. D.; Vieira, E. F.
Along the life of the IUE project, a large archive with spectral data has been generated, requiring automated classification methods to be analyzed in an objective form. Previous automated classification methods used with IUE spectra were based on multivariate statistics. In this paper, we compare two classification methods that can be directly ap…
A study of emission lines variability of the active galaxy PKS 0521-365.
Pian, E.; Falomo, R.; Scarpa, R.
Optical spectrophotometry of the active galaxy PKS 0521-365 over a period of 7 years is reported, together with the analysis of IUE archival spectra. The Hα emission line intensity varied by more than a factor of 2 during the monitoring. Similar amplitude variations are observed in the optical and UV continuum, which however are not simply correla…
Radial and Meridional Trends in Solar Wind Thermal Electron Temperature and Anisotropy: ULYSSES
Forsyth, R. J.; Bame, S. J.; Scime, E. E. +3 more
Ulysses plasma measurement from 1.15 to 5.31 AU and from S6.4° to S48.3° solar latitude are used to assess the trends in the solar wind thermal electron temperature and anisotropy. Improved spacecraft potential corrections and data products have been incorporated. The radial temperature gradient is steeper than in previous determinations, but flat…
Large-Scale Interplanetary Magnetic Field Configuration Revealed by Solar Radio Bursts
Stone, R. G.; Fainberg, J.; Reiner, M. J.
An instantaneous view of the interplanetary extension of the solar magnetic field is provided here by measurements from a space platform at high ecliptic latitudes of the trajectories of individual type III solar radio bursts. The Ulysses spacecraft provides this unique vantage point with an orbit taking it far from the ecliptic plane. The Ulysses…
New Insights into Nonradiative Heating in Late A Star Chromospheres
Walter, Frederick M.; Linsky, Jeffrey L.; Matthews, Lynn D.
Using new and archival spectra from the Goddard High Resolution Spectrograph, we have searched for evidence of chromospheric and transition region emission in six stars of mid to late A spectral type. Two of the stars, α Aql (A7 IV-V) and alpha Cep (A7 IV-V), show emission in the C II 1335 Å doublet, confirming the presence of hot plasma with temp…
Hot HB stars in globular clusters: physical parameters and consequences for theory. II. NGC 6397 and its short blue horizontal branch.
de Boer, K. S.; Heber, U.; Schmidt, J. H. K.
New visual spectra of 14 blue horizontal-branch (BHB) stars in NGC 6397 and 2 spectra from the literature are used to derive atmospheric parameters (T_eff_, logg) for these stars. With the theoretical surface brightness for the derived stellar parameters and with the given distance of the cluster one then can calculate the radius, the luminosity, …
Astrometry of double stars with HIPPARCOS
Badiali, M.; Cardini, D.; Emanuele, A. +13 more
After the processing of 30 months of the observations carried out by HIPPARCOS it is possible to provide reliable statistics on the number of double and multiple stars to be detected at the mission completion and on the quality of the astrometric and photometric results on these objects. About 21000 stars have been recognized as non-single, includ…
Latitudinal structure of a coronal mass ejection inferred from Ulysses and Geotail observations
Balogh, A.; Phillips, J. L.; Gosling, J. T. +7 more
We present the first observations of a CME by two spacecraft separated substantially in heliographic latitude. Ulysses and Geotail both see similar features in the plasma and magnetic field parameters during an interval in which Geotail is located in the deep magnetosheath (>150 RE) and Ulysses is located in the solar wind at 5 AU, ∼…
Diffuse interstellar bands and UV extinction curves. The missing link.
Desert, F. -X.; Jenniskens, P.; Dennefeld, M.
The connection between diffuse interstellar bands and components of the interstellar ultraviolet extinction curve, decomposed according to the Fitzpatrick & Massa scheme, is analysed from new observations of several DIBs in the line of sight to 28 stars measured by IUE. We find that the strength of the 217.5nm bump positively correlates with D…
The Structure of Wolf-Rayet Winds. I. Observation of Ionization Stratification in WR 6 and WR 111
Schulte-Ladbeck, Regina E.; Eenens, Philippe R. J.; Davis, Kevin
Although it is widely believed that the winds of Wolf-Rayet stars are driven by radiation pressure, a major problem has been to explain theoretically the observation of very efficient conversion of radiative momentum to the gas. Known as the "momentum problem," this has led to alternative models in which the radiation force is only one of the forc…