Search Publications

Simulated imaging of the upper atmosphere of active stars

Donati, J. -F.; Catala, C.

We have applied the principles of indirect stellar surface imaging (Doppler imaging) for simulated mapping of active regions in the upper atmosphere of cool active stars. Our tests illustrate how synthetic distributions at the chromosphere or transition region level can be recovered from time series of high resolution profiles of UV lines, as sate…

X-Ray Ultraviolet and Far Infrared Emission of Seyfert Galaxies

Mas-Hesse, J. M.; Rodriguez-Pascual, P. M.; Mirabel, I. F. +3 more

We have compiled multiwavelength data (in the radio, FIR, optical, UV and X-ray ranges) for a sample of 126 galaxies, including QSO, Seyfert 1, Seyfert 2 and galaxies dominated by star-forming processes. We have tested the implications of "unified Seyfert models", which assume that Seyfert 1 and 2 galaxies are intrinsically the same kind of object…

IUE Observations of Highly Ionized Gas toward Distant Stars in the Milky Way

Sembach, Kenneth R.

Combined high-dispersion IUE spectra of interstellar Si IV, C, IV, and N V absorption along distnat lines toward early type stars in the Galactic disk and low halo are discussed. The highly ionized species have complex profiles and exhibit stronger absorption toward distant low latitude stars than toward high latitude stars. Absorption along low l…

The presence of fe VII and of low-ionization features in the UV spectra of central stars of planetary nebulae.

Tweedy, R. W.

The correlation between the presence of N I and Fe VII absorption lines in the spectra of central stars of planetary nebulae reported by Feibelman & Bruhweiler (1990) and Cheng et al. (1991) is refuted. Many spectra that they discuss are severely underexposed; moreover, 12 of them reveal no continuum whatsoever. These therefore cannot be used …

Evolution of SN 1987A in the ultraviolet.

Sanz Fernandez de Cordoba, L.

Two observational aspects of the evolution of SN 1987A in the UV are presented, based on IUE data. First, the spectral evolution of the NV, NIV], HeII, OIII], NIII] and CIII] emission lines in the period from March 13, 1987 to March 12, 1990. And secondly, the evolution of the SN 1987A continuum fluxes in various UV bands using SWP and LWP spectra…

An Evidence for Gaseous Envelope Surrounding the RS CVn System lambda And

Glebocki, R.; Sikorski, J.

MgII h and k profiles are analyzed in 62 high dispersion IUE spectra of a long-period RS CVn binary lambda And. We find strong evidence of the presence of circumstellar matter surrounding the binary system. Estimated lower mass limit of the envelope is 6.6 times 10^{-14} M_odot. We present evidence for the changes with time of the perias…

COMPTEL Observation of GRB 930131

Greiner, J.; Hanlon, L.; Schönfelder, V. +11 more

Ephemerides of the 48 HIPPARCOS minor planets for the year 1993

Bec-Borsenberger, A.

To be observed by Hipparcos, the position of each object has to be known with an accuracy of 1 arcsecond and its magnitude with an accuracy of 0.5 mag. Therefore, the orbital elements of the 48 selected minor planets of the Hipparcos mission, have been improved in order to extrapolate their ephemerides with the accuracy required. Updated ephemerid…

Silicon Abundances in Population I Giants

Bohm-Vitense, Erika

Silion to carbon abundance ratios for Population I giants were determined from emission lines originating in the transition layers between stellar chromospheres and coronae. For effective temperatures larger than 6200 K we find a group of stars for which the silicon to carbon abundance ratio appears to be increased. These stars are presumably desc…

Low Energy Ion and Electron Events at Ulysses Beyond 5 AU and at IMP8 near Earth

Simnett, G. M.; Lanzerotti, L. J.; Roelof, E. C. +1 more