Search Publications
Long- and short-term variability in O-star winds. I. Time series of UV spectra for 10 bright O stars.
Kaper, L.; Henrichs, H. F.; Nichols, J. S. +3 more
An atlas of time series of ultraviolet spectra is presented for 10 bright O stars. The spectra were obtained with the International Ultraviolet Explorer during seven observing campaigns lasting several days over a period of 6years. The UV P Cygni lines in 9 out of the 10 studied stars exhibit a characteristic pattern of variability in the form of …
The β Pictoris phenomenon among Herbig Ae/Be stars. UV and optical high dispersion spectra.
Talavera, A.; McCollum, B.; Sitko, M. L. +10 more
We present a survey of high dispersion UV and optical spectra of Herbig Ae/Be (HAeBe) and related stars. We find accreting, circumstellar gas over the velocity range +100 to +400km/s, and absorption profiles similar to those seen toward β Pic, in 36% of the 33 HAeBe stars with IUE data as well as in 3 non-emission B stars. We also find evidence of…
Planetary nebulae in the Magellanic Clouds. I. Carbon abundances and TypeI PNe.
Dennefeld, M.; Leisy, P.
We present optical and ultraviolet spectroscopic observations of planetary nebulae (PNe) in the Large (LMC) and the Small Magellanic Clouds (SMC). For the visible spectra with highest S/N, line intensities have been measured to a few tenths of a percent of Hbeta_. UV spectra are used for the determination of carbon abundances. This pape…
A new maximum likelihood method for luminosity calibrations.
Luri, X.; Figueras, F.; Torra, J. +1 more
A new statistical parallax method using the Maximum Likelihood principle is presented, allowing the simultaneous determination of a luminosity calibration, kinematic characteristics and spatial distribution of a given sample. This method has been developed for the exploitation of the Hipparcos data and presents several improvements with respect to…
Photometric and spectroscopic studies of cool stars discovered in EXOSAT X-ray images. III. Photometric properties.
Tagliaferri, G.; Pasquini, L.; Pallavicini, R. +2 more
We present high-precision UBV(RI)_c_ photometry for a sample of active stars detected serendipitously by the EXOSAT satellite. Fourteen objects, out of 47 likely optical counterparts, turned out to be clearly variable, with periods in the range 1-8 days, including a newly discovered eclipsing binary. For most of them the optical variability is con…
The canonical X-ray/gamma-ray spectrum of Seyfert 1s and low-state Galactic black hole candidates.
Zdziarski, A. A.; Magdziarz, P.; Gierlinski, M. +1 more
We review broad-band X-ray/γ-ray spectra of radio-quiet Seyfert 1s as well as of Galactic black hole candidates in the low state. The spectra share their basic components: an underlying power law, a Compton-reflection component with an Fe Kα line, low-energy absorption by cold matter, and a high-energy cutoff above ~200keV. The X-ray energy spectr…
Azimuthal structures in the wind and chromosphere of the Herbig AE star AB Aurigae. Results from the MUSICOS 1992 campaign.
Talavera, A.; Donati, J. -F.; Semel, M. +19 more
The observations of the MUSICOS 1992 campaign concerned three scientific programs, among which was the study of azimuthal structures in the wind and chromosphere of the pre-main sequence Herbig Ae star AB Aur. The He I 5876A line of AB Aur, which is formed in the expanding chromosphere of this star, most probably in the innermost parts of its wind…
Radial velocities and axial rotation for a sample of chemically peculiar stars.
Morrell, N.; Levato, H.; Grosso, M. +2 more
As part of a systematic project we have determined radial velocities and projected rotational velocities for a sample of 186 chemically peculiar stars which have been observed by the Hipparcos' satellite. The purpose is to provide necessary data to study the space velocities of peculiar stars.
Determination of interstellar helium parameters from the ULYSSES-NEUTRAL GAS experiment: Method of data analysis.
Rosenbauer, H.; Witte, M.; Banaszkiewicz, M.
The GAS instrument on board the ULYSSES spacecraft has, for the first time, measured directly the interstellar flux of helium atoms in the inner solar system. From the locally measured angular distribution of the flux, the task is to derive the five parameters of the Maxwellian distribution function: density, bulk velocity vector, and temperature …
Multi-colour photometric and spectroscopic monitoring of the WN5 star EZ Canis Majoris.
van der Hucht, K. A.; van Genderen, A. M.; Duijsens, M. F. J. +3 more
We present and analyse photometric and spectroscopic observations of the WN5 star EZ Canis Majoris obtained over a period of 7years. We discuss the changing light curve, the shift in phase of the maxima and point to flare type variability seen in one night. Small amplitude variations are reported in another night. We have investigated the change o…