SIMBAD references

2002A&A...381.1007R - Astronomy and Astrophysics, volume 381, 1007-1014 (2002/1-3)

Spectral analysis of the sdO Ps1 in the globular cluster M 15 (NGC 7078).


Abstract (from CDS):

We present a spectral analysis of the sdO central star K648 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 Teff=39±2kK and logg=3.9±0.2. The helium (nHe/nH=0.08) and oxygen (nO/nH=0.001) abundances are about solar while carbon is enriched by a factor of 2.5 (nC/nH=0.001). Nitrogen (nN/nH=1x10–6, [N/H]=-2.0) appears at a sub-solar value. However, these metal abundances are much higher than the cluster's metallicity (M 15: [Fe/H]=-2.25). The surface composition appears to be a mixture of the original hydrogen-rich material and products of helium burning (3α 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 logTeff-logg plane with evolutionary calculations a mass of 0.57+0.02–0.01M and a luminosity of 3810±1200L are deduced. Our spectroscopic distance d=11.1+2.4–2.9kpc is in agreement with the distance of M 15 as determined by Alves et al. (2000AJ....120.2044A). From the GHRS spectra we measure a radial velocity of vrad=-130km/s.

Abstract Copyright:

Journal keyword(s): Galaxy: globular clusters: individual: M 15 - ISM: planetary nebulae: individual: Ps1 - stars: abundances - stars: AGB and post-AGB - stars: evolution - stars: individual: K648

Status at CDS:  

Simbad objects: 2

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