Search Publications
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…
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} Modot. We present evidence for the changes with time of the perias…