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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…
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…
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…
Ultraviolet properties of early-type galaxies.
Alloin, D.; Pastoriza, M. G.; Bonatto, C. +1 more
We analyse the UV properties of early-type galaxies from their UV spectra in the IUE library, including both normal and active nuclei. We co-added the spectra, and hence the objects into groups of similar spectral properties in the UV, also taking into account their properties in the visible/near-infrared ranges. Although, owing to the presence of…
First Cycle 4 multiwavelength observations of the gamma-ray quasar PKS 0208-512.
Vestrand, W. T.; Sreekumar, P.; Kubo, H. +3 more
We present first results of CGRO Cycle 4 multiwavelength observations of the gamma-ray quasar PKS 0208-512. A bright, variable gamma-ray source, PKS 0208-512 has been detected numerous times by the EGRET experiment aboard the CGRO, possessing one of the hardest spectra observed to date. The recent COMPTEL observations of Blom et al. (1995A&A..…
Probable detection of high-energy gamma-ray emission from OJ 287 during a major optical flare.
Shrader, C. R.; Hartman, R. C.; Webb, J. R.
We observed the BL Lac object OJ 287 with the CGRO/EGRET instrument as a target of opportunity triggered by an outburst in its visual intensity. OJ 287 is well known as a high-amplitude variable in the optical and radio domain, and recurrent outburst behavior at nominal 11.6-year intervals have led to speculation that there may be some determinist…
A library of IUE white dwarf spectra for stellar population analyses.
Bonatto, C.; Bica, E.; Giovannini, O.
We present high Signal to Noise ratio IUE spectra of different classes of white dwarfs, to be used as templates for stellar population analyses in the ultraviolet region. We present average stellar parameters associated to each group. The library contains 6 groups for DA's, 2 for DO's and 5 for DB's. We also present equivalent widths of spectral f…