Search Publications
Solar transition region line broadening: Limb to limb measurements
Doyle, J. G.; Teriaca, L.; Banerjee, D.
Full disk images from SUMER/SoHO taken in He I, C IV and Ne VIII are used to investigate whether there exists a center-to-limb variation in the line width. Both C IV and He I show such a variation but the higher temperature Ne VIII line is relatively constant. For C IV, this corresponds to ~ 3 km s-1 difference while He I is significant…
ISO observations of the BL Lacertae object PKS 2155-304
Maraschi, L.; Tagliaferri, G.; Ghisellini, G. +5 more
The BL Lacertae object PKS 2155-304 was observed by the Infrared Space Observatory in May and June 1996, during a multiwavelength campaign. These are the first observations in the mid- and far-infrared bands since IRAS. In the observing period, the source showed no detectable time variability at 4.0, 14.3, 60 and 90 mu m. The spectrum from 2.8 to …
First results of UVES at VLT: revisiting RR Tel
Bonifacio, P.; Selvelli, P. L.
We present here the first results of UVES observations of RR Tel. The exceptional performances of the instrument have allowed the detection of new spectral features and have led to an improvement in the identifications of several emission lines. A direct comparison with the IUE observations in the range 3045-3300 Åhas revealed the appearance of ma…
UV spectra of T Tauri stars from Hubble Space Telescope: RW Aur
Vittone, A. A.; Errico, L.; Lamzin, S. A.
Ultraviolet spectra of the classical T Tauri star RW Aur A observed with the Hubble Space Telescope were analysed. Absorption lines of neutral and singly ionized metals, blueshifted ~ 50 km s-1 relative to the star, were found. They originate in a dense (N>1010 cm-3) gas outflow, whose extension along the line o…
Chromospheric two-component NLTE modelling of the binary system V 711 Tau = HR 1099
Lanzafame, A. C.; Rodonò, M.; Busà, I.
In this paper we present the first two-component, semi-empirical chromospheric model of the RS CVn binary system V 711 Tau based on detailed fits of Hα and Mg II h line profiles. Synthetic Hα and Mg II h line profiles are computed by means of NLTE radiative transfer calculations. Using the observed Emission Measure distribution to constrain the tr…
FIP effect measurements in the off-limb corona observed by SUMER on SOHO
Dwivedi, B. N.; Mohan, A.; Landi, E.
Systematic differences between elemental abundances in the corona and in the photosphere have been long acknowledged in the Sun; these abundance anomalies are correlated with the first ionization potentials (FIPs) of the elements. This correlation is called FIP effect. Using spectra obtained from the SUMER (Solar Ultraviolet Measurements of Emitte…
A-shell stars in the Geneva system
Jaschek, C.; Hauck, B.
Among the various kinds of A stars having a peculiar spectrum, we find the A-shell stars. Many questions are still open concerning these stars, including their evolutionary status. In the present study we have used data from the Hipparcos catalogue to examine this point. We have found that the majority of A-shell stars are well above the main sequ…
The collision strength of the [Ne v] infrared fine-structure lines
Beintema, D. A.; Ferland, G. J.; van Hoof, P. A. M. +1 more
The calculation of accurate collision strengths for atomic transitions has been a long standing problem in quantitative spectroscopy. Most modern calculations are based on the R-matrix method and problems pertaining to the use of this method have led to a discussion of the accuracy of these results. More in particular, based on an analysis of the …
Star formation in distant starburst galaxies
Alloin, D.; Pastoriza, M. G.; Bonatto, C. +1 more
This paper discusses the stellar population content of distant (5 000 km s^{-1} <== V_R<=16 000 km s^{-1}) galaxies with enhanced star-formation activity. Distinction is made between isolated galaxies and galaxies morphologically disturbed, with clear signs of interaction such as mergers. In these galaxies the International Ultraviolet Explo…
Emerging flux as a driver for homologous flares
Culhane, J. L.; Harra, L. K.; Matthews, S. A. +1 more
We present multi-wavelength observations of 2 M-class solar flares observed by SoHO and Yohkoh, which appear to be homologous. By examination of the flare loop morphology and footpoints we propose a schematic reconnection scenario of a two loop interaction in a quadrupolar magnetic configuration, for both flares (Machado ?; Mandrini ?). After the …