Search Publications
Ultraviolet DIB at 1369 A Arising in Molecular Clouds
Gnacinski, P.; Sikorski, J.; Kaczmarczyk, G.
Hubble Space Telescope (HST) and IUE observations of the weak unidentified interstellar line 1369 A in nine early type stars are discussed. This absorption feature might be a diffuse interstellar band (DIB). We have found good correlation between the equivalent widths of the 1369 A line and the interstellar CO A1Pi-X1Sigma (6…
Ultraviolet Ionization Stratification in Wolf-Rayet Winds
Rochowicz, Krzysztof
Ionization stratification can be used to study the structure of WR winds. In an accelerated outflow the stratification is observable through the Doppler effect as an inverse correlation of ionization potential (IP) with line width (FWHM). However, not only the average line widths of different ions, but also the line widths of one series of HeII sh…
Starspot and Chromospheric Activity of lambda And in 1978--1995
Glebocki, R.; Sikorski, J.
UBV photometry and UV spectra from the IUE satellite are analyzed for search of relation between photospheric and chromospheric activity in lambda And. We find no correlation between intensity variations of chromospheric and TR emissions and visibility of spots. Intensities of TR lines are proportional to the MgII emissions. UV continuum follows f…
Terminal Velocities of Wolf-Rayet Star Winds from Low Resolution IUE Spectra
Niedzielski, A.; Rochowicz, K.
Attracted by the simplicity of the recently published by Prinja (1994) method of determination of terminal wind velocities in hot stars from low resolution IUE spectra we investigate its application to WR stars. With a large sample of low resolution IUE spectra of WR stars we found even simpler, that is linear instead of square, empirical relation…
Non-standard Extinction by Circumnuclear Dust in Active Galactic Nuclei
Szczerba, R.; Madejski, G.; Czerny, B. +2 more
Observational data imply that Active Galactic Nuclei are likely to have a substantial amount of dust within some 0.1-100pc. This dust modifies the observed spectrum of the nucleus by reprocessing a significant fraction of its intrinsic bolometric luminosity. The details of the emerging spectrum in the infrared and in the ultraviolet are dependent …
Interstellar Ultraviolet Extinction Towards the Nitrogen Sequence Wolf-Rayet Stars
Niedzielski, Andrzej
With the archive IUE spectra of WR stars collected by Niedzielski and Rochowicz (1994) we obtain the UV extinction curve for WN stars. Using the two-color diagram method we can reach the goal almost independently, assuming only similar (b-v)_0 for all single galactic WN stars, what is discussed on the basis of latest results. The resulting extinct…
Local Interstellar Medium Toward beta GEM and sigma GEM
Glebocki, R.; Gnacinski, P.; Sikorski, J.
We present and analyze high-dispersion IUE observations of the interstellar magnesium, deuterium and hydrogen absorption profiles toward two late-type stars beta Gem (10.8 pc) and sigma Gem (59 pc) separated by 0.5 arcdeg on the sky. We confirm the velocity shift of the local interstellar cloud obtained for a bulk flow by Crutcher (1982). From the…
Quantitative Spectroscopy of K 648 --the PNN of Ps1 in the Globular Cluster M15
Dreizler, Stefan; Werner, Klaus; Heber, Ulrich
We report preliminary results of a quantitative study of high resolution UV and optical spectra of K648 obtained with the Hubble Space Telescope and the Calar Alto 3.5 m telescope, respectively. Using state of the art NLTE model- atmospheres we determine atmospheric parameters and the abundances of hydrogen, helium and carbon. K648 is found to be …
Asteroseismology of Planetary Nebula Nuclei
Bond, Howard E.; Ciardullo, Robin; Kawaler, Steven D.
Nine PNNs are now known to be pulsating variables. All of them are OVI or PG1159-type objects, with extreme hydrogen deficiency and high abundances of C and O. They are non-radial pulsators, with typical periods of 10 to 30 min, and their probable descendants are the shorter-period GW Vir (PG) pulsating white dwarfs whose PNe have presumably dispe…
On Mode Identification in delta Scuti
Cugier, H.; Monier, R.
UV light amplitudes and phase shifts obtained from the IUE observations are discussed for pulsating star delta Scuti. The published ground-based photometric and radial velocity data are also included in the analysis. The observations are compared with model calculations which take into account temperature and pressure changes during pulsation cycl…