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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…