Search Publications
Star formation and extinction in extragalactic H II regions.
Kunth, D.; Deharveng, J. M.; Lequeux, J. +1 more
Evolutionary models are presented of far UV luminosity, production of ionizing photons, effective temperature, and ejection of heavy elements for an ionizing star cluster. The way in which interstellar extinction in our Galaxy and inside and outside the H II region affects the UV and optical emission of the complex is discussed. Conclusions are de…
3C 273 revisited : confirmation by COS-B of high energy gamma-ray emission.
Caraveo, P. A.; Bignami, G. F.; Hermsen, W. +11 more
The results of a second observation in the Virgo region by the ESA COS-B satellite are presented. The presence of a high- energy (50-800 MeV) gamma-radiation source is confirmed, and its position is consistent with 3C273. The error box at the 90% confidence level containing the quasar is ∼2.5 square degrees, and the probability of a chance coincid…
A model of V1016 CYG based on the ultraviolet spectrum.
Nussbaumer, H.; Schild, H.
The ultraviolet spectrum of the suspected symbiotic star V 1016 Cygni is interpreted in terms of a single star model. Spectra were obtained at low and high resolutions in the range 1100 to 3200 A by the IUE. From analyses of spectral features including the forbidden Ne V lines, He II UV recombination lines and the continuum flux, an interstellar r…
IUE spectroscopy of cataclysmic variables.
Vogt, N.; Wolf, B.; Krautter, J. +4 more
The continuum flux distribution and line spectra of six cataclysmic variables detected by the IUE are studied. The spectrophotometry with intermediate spectral resolution around seven A allows derivation of extinction values, temperatures, and the sizes of the radiating areas. V603 Aql, RRpic, HRDel, and TT Ari, which have similar absolute dimensi…
Search for gamma-radiation from extragalactic objects using a likelihood method.
Bignami, G. F.; Hermsen, W.; Masnou, J. L. +5 more
A search through COS-B data for gamma-radiation from a number of extragalactic objects reveals no strong evidence for any positive identification except, as already reported, for the region around the quasar 3C273. Upper limits to the photon fluxes from active extragalactic objects are evaluated using a likelihood method. They reinforce the conclu…
A change in light curve asymmetry and the ephemeris of CYG X-3.
van der Klis, M.; Bonnet-Bidaud, J. M.
Cygnus X-3 was observed in the 2-12 keV range for 40 days in May-June 1980. The mean 4.8 h light curve was seen to change significantly in a way suggestive of the existence of an underlying binary with an eclipse duration of 40 percent of the period. The observed time of X-ray minimum was found to increase the level of confidence of a period deriv…
IUE and ground-based spectroscopic observations of the S Dor-type LMCvariable R 71 during minimum state.
Stahl, O.; Wolf, B.; Appenzeller, I.
Using the IUE satellite, high resolution UV spectrograms are obtained of the S Dor type variable R 71 in the LMC. The IUE observations are supplemented by coordinated ground-based high dispersion spectroscopy and photometric observations. For the expanding envelope, a surprisingly low temperature of only about 6000 K and an apparently decelerated …
Ultraviolet extinction in the Small Magellanic Cloud.
Ferlet, R.; Lequeux, J.; Prevot, L. +2 more
The considered investigation is concerned with the determination of the UV extinction curve in the Galaxy on the basis of the spectra of stars in the SMC obtained with the aid of the International Ultraviolet Explorer. The determination rests on the comparison of the observed spectral energy distribution of pairs of similar stars with different ex…
Mass loss from O subdwarfs.
Kudritzki, R. P.; Hamann, W. -R.; Gruschinske, J. +1 more
The P Cygni profiles are reproduced by comoving frame calculations, and a determination is made of the wind parameters. Lower limits of mass loss for these stars (HD 49798 and HD 128220 B) are derived, and upper limits for all four objects are estimated on the basis of general considerations. The empirical results are compared with the available t…
R 81 : P CYG of the LMC.
Stahl, O.; Sterken, C.; Wolf, B. +1 more
Photometric UBV observations and spectroscopic high dispersion coude observations of the very luminous B2.5 eq supergiant R 81 of the LMC carried out between 1970 and 1980 at ESO, La Silla, are discussed. It is noted that the most prominent features of the visual spectrum are P Cygni profiles of the Balmer lines, which are thought to indicate a sh…