Search Publications
Magnetic structure in cool stars. XVI. Emissions from the outer atmospheres of M-type dwarfs.
Mewe, R.; Rutten, R. G. M.; Schrijver, C. J. +2 more
Consideration is given to emission from the outer atmospheres of M-type dwarfs in several spectral lines originating from the chromosphere, the transition-region, and the soft X-ray emission from the corona. It is shown that M-type dwarfs systematically deviate from relations between flux densities in soft X-rays and chromospheric and transition-r…
The circumstellar gas around beta Pictoris. VIII. Evidence for a clumpy structure of the infalling gas.
Ferlet, R.; Vidal-Madjar, A.; Beust, H. +1 more
In a recent paper, the variable and redshifted circumstellar lines of ionized elements in the UV spectrum of Beta Pictoris were studied. The Al III doublet has been investigated, using both archival and recent IUE spectra of Beta Pic. This larger set of data is used to derive some general characteristics of the variable Al III lines. In particular…
Rotational modulation and flares on RS Canum Venaticorum and BY Draconis.stars. X. The 1981 October 3 flare on V711 Tauri (= HR 1099).
Linsky, J. L.; Simon, T.; Neff, J. E. +5 more
We present a unique set of high resolution spectra of V71 1 Tauri = HR 1099 (G5 V + K1 IV) obtained with both the SWP and LWR cameras of lUE, together with simultaneous 6.4 GHz microwave emission and optical photometry, during a bright flare on 3 October 1981. The electron density of the flaring plasma at 6 104K was about 11011
Ultraviolet flares on II Pegasi.
Doyle, J. G.; Byrne, P. B.; van den Oord, G. H. J.
UV spectroscopic observations of the RS CVn star, II Peg, were obtained in February 1983. The observations show evidence for flare activity in greatly enhanced chromospheric and transition region emission lines. The flare radiation is isolated and the electron pressures of the mean quiescent atmosphere and the two flares are derived from the inter…
EXOSAT observations of five luminous globular cluster X-ray sources.
Stella, L.; Parmar, A. N.; Giommi, P.
Exosat observations are used to search for orbital modulations in the X-ray light curves of five luminous globular cluster X-ray sources in NGC 1851, NGC 6441, NGC 6712, Terzan 1, and Terzan 2. Upper limits to possible short-period orbital modulation are presented. Two or three intensity dips are observed in the light curve of NGC 6441. The result…
The UV silicon spectra of early B stars.
Massa, D.
Equivalent widths of UV silicon lines obtained from high dispersion IUE SWP spectra for a sample of 37 mid- to early B stars are presented. These are compared to other atmospheric diagnostics and to model atmosphere calculations. It is found that some of the UV silicon lines are extremely sensitive to stellar temperature and luminosity over the ra…
Long- and short-term variability of the T Tauri star RY Lupi.
Liseau, R.; Gahm, G. F.; Fischerstrom, C. +1 more
Data are presented on spectroscopic and photometric observations of the T Tauri star RY Lupi carried out since 1981 from the FUV to the IR spectral region. These data show a remarkable kind of variability of the RY Lupi. Namely, the FUV and the IR fluxes, as well as the fluxes in H-alpha and H-beta are relatively constant, while the range in V mag…
The colour of Comet P/Halley's nucleus and dust
Keller, H. U.; Thomas, N.
Results are presented on the absolute calibration of the Halley Multicolor Camera (HMC), showing that HMC is 24 less sensitive than previously thought. The results are used to determine the reflectivity of the nuclear surface of the P/Halley comet, its color, and the color of the dust within 300 km of the nucleus. Results showed that the nucleus o…
Active phenomena in the pre-main sequence Herbig AE star HD 163296.
Talavera, A.; Catala, C.; Simon, T. +3 more
Observations by IUE of the short-term variability of the Mg II and Ca II resonance lines in the Herbig Ae star HD 163296 are presented. Evidence that these lines show a phenomenon of rotational modulation, similar to the one observed in AB Aur, another Herbig Ae star is found. The variations in the spectrum of HD 163296 are even more conspicuous t…
Effective temperatures of AP stars.
Stepien, K.; Dominiczak, R.
A new method of determination of the effective temperatures of Ap stars is suggested in which at first the temperature of a model best reproducing the observed visual energy distribution is determined and then a correction to this temperature resulting from the UV flux deficit is added. The method is calibrated on a sample of stars with energy dis…