| Issue |
A&A
Volume 381, Number 3, JanuaryIII 2002
|
|
|---|---|---|
| Page(s) | 1007 - 1014 | |
| Section | Stellar structure and evolution | |
| DOI | https://doi.org/10.1051/0004-6361:20011535 | |
| Published online | 15 January 2002 | |
Spectral analysis of the sdO K 648, the exciting star of the planetary nebula Ps 1 in the globular cluster M 15 (NGC 7078)*
1
Institut für Astronomie und Astrophysik, Universität Tübingen, 72076 Tübingen, Germany
2
Dr. Remeis-Sternwarte, Universität Erlangen-Nürnberg, 96049 Bamberg, Germany
Corresponding author: T. Rauch, rauch@astro.uni-tuebingen.de
Received:
17
July
2001
Accepted:
29
October
2001
We present a spectral analysis of the sdO central star K 648 based on medium-resolution
optical and high-resolution UV spectra. The photospheric parameters are determined by means
of state-of-the-art NLTE model atmosphere techniques.
We found and . The helium ()
and oxygen () abundances are about solar while carbon is enriched by a factor
of 2.5 ().
Nitrogen (, 
) appears at a sub-solar value.
However, these metal abundances are much higher than the cluster's metallicity (M 15: 
).
The surface composition appears to be a mixture of the original hydrogen-rich material
and products of helium burning (
process) which have been mixed up to the surface.
The abundances of He, C, and N are consistent with the nebular abundance, while O is
considerably more abundant in the photosphere than in the nebula.
From a comparison of its position in the 
–
plane with evolutionary
calculations a mass of 
and a
luminosity of 
are deduced.
Our spectroscopic distance 
is in agreement with the
distance of M 15 as determined by Alves et al. (2000).
From the GHRS spectra we measure a radial velocity of 
.
Key words: Galaxy: globular clusters: individual: M 15 / ISM: planetary nebulae: individual: Ps 1 / stars: abundances / stars: AGB and post-AGB / stars: evolution / stars: individual: K 648
Based on observations obtained at the German-Spanish Astronomical Center, Calar Alto, operated by the Max-Planck-Institut für Astronomie Heidelberg jointly with the Spanish National Commission for Astronomy, on data retrieved from the International Ultraviolet Explorer (IUE) Final Archive, on observations made with the Hubble Space Telescope (HST, GO Proposal ID: 3513, PI: Heber), and on HST data retrieved from the ST-ECF archive.
© ESO, 2002
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.