The far-ultraviolet spectra of two hot PG1159 stars

Abstract

PG1159 stars are hot, hydrogen-deficient (pre-) white dwarfs with atmospheres mainly composed of helium, carbon, and oxygen. The unusual surface chemistry is the result of a late helium-shell flash. Observed element abundances enable us to test stellar evolution models quantitatively with respect to their nucleosynthesis products formed near the helium-burning shell of the progenitor asymptotic giant branch stars. Because of the high effective temperatures (Teff), abundance determinations require ultraviolet spectroscopy and non-local thermodynamic equilibrium model atmosphere analyses. Up to now, we have presented results for the prototype of this spectral class and two cooler members (Teff in the range 85,000-140,000 K). Here we report on the results for two even hotter stars (PG1520+525 and PG1144+005, both with Teff = 150,000 K) which are the only two objects in this temperature-gravity region for which useful far-ultraviolet spectra are available, and revisit the prototype star. Previous results on the abundances of some species are confirmed, while results on others (Si, P, S) are revised. In particular, a solar abundance of sulphur is measured in contrast to earlier claims of a strong S deficiency that contradicted stellar evolution models. For the first time, we assess the abundances of Na, Al, and Cl with newly constructed non-LTE model atoms. Besides the main constituents (He, C, O), we determine the abundances (or upper limits) of N, F, Ne, Na, Al, Si, P, S, Cl, Ar, and Fe. Generally, good agreement with stellar models is found.

arXiv commentAccepted for publication in A&A

References in corpus (19)

• The chemical composition of the Sun
• Post-Asymptotic Giant Branch Evolution of Low- and Intermediate-Mass Stars. Preliminary Results
• New models for the evolution of Post-Asymptotic Giant Branch stars and Central Stars of Planetary Nebulae
• The Element Abundances in Bare Planetary Nebula Central Stars and the Shell Burning in AGB Stars
• The WIRED Survey II: Infrared Excesses in the SDSS DR7 White Dwarf Catalog
• The deuterium-to-oxygen ratio in the interstellar medium
• New evolutionary sequences for hot H-deficient white dwarfs on the basis of a full account of progenitor evolution
• Identification of neon in FUSE and VLT spectra of extremely hot hydrogen-deficient (pre-) white dwarfs
• Asteroseismological measurements on PG 1159-035, the prototype of the GW Vir variable stars
• Discovery of photospheric argon in very hot central stars of planetary nebulae and white dwarfs
• High-resolution ultraviolet spectroscopy of PG1159-035 with HST and FUSE
• Including All the Lines
• Iron abundance in hot hydrogen-deficient central stars and white dwarfs from FUSE, HST, and IUE spectroscopy
• Is the Sulphur Anomaly in Planetary Nebulae Caused by the s-Process?
• Asteroseismology of hot pre-white dwarf stars: the case of the DOV stars PG 2131+066 and PG 1707+427, and the PNNV star NGC 1501
• Identification of NeVIII lines in H-deficient (pre-) white dwarfs: a new tool to constrain the temperature of the hottest stars
• Iron abundance in the prototype PG1159 star, GW Vir pulsator PG1159-035, and related objects
• The far-ultraviolet spectra of "cool" PG1159 stars
• Chandra grating spectroscopy of three hot white dwarfs

Cited by in corpus (7)

• Catalogue of central stars of planetary nebulae: Expanded edition
• Spectral analysis of the hybrid PG 1159-type central stars of the planetary nebulae Abell 43 and NGC 7094
• Stellar parameters for the central star of the planetary nebula PRTM 1 using the German Astrophysical Virtual Observatory service TheoSSA
• The hot white dwarf in the peculiar binary nucleus of the planetary nebula EGB6
• The Impact of the Third Dredge-up and Mass Loss in Shaping the Initial-Final Mass Relation of White Dwarfs
• How an overweight and rapidly rotating PG 1159 star in the Galactic halo challenges evolutionary models
• Stars on the ascending helium giant branch I. From white dwarf merger to helium giant: the evolutionary state of the rapidly rotating hot subdwarf HE 1518-0948