"Orbital Parameters And Chemical Composition Of Four White Dwarfs In Po" by Adéla Kawka, Stéphane Vennes et al.
 

Document Type

Article

Publication Title

The Astrophysical Journal

Abstract

We present FUSE observations of the hot white dwarfs in the post-common-envelope binaries Feige 24, EUVE J0720-317, BPM 6502, and EUVE J2013+400. The spectra show numerous photospheric absorption lines, which trace the white dwarf orbital motion. We report the detection of C III, O VI, P V, and Si IV in the spectra of Feige 24, EUVE J0720-317, and EUVE J2013+400 and the detection of C III, N II, Si III, Si IV, and Fe III in the spectra of BPM 6502. Abundance measurements support the possibility that white dwarfs in post-common-envelope binaries accrete material from the secondary star wind. The FUSE observations of BPM 6502 and EUVE J2013+400 cover a complete binary orbit. We used the FUSE spectra to measure the radial velocities traced by the white dwarf in the four binaries, where the zero-point velocities were fixed using the ISM velocities in the line of sight of the stellar systems. For BPM 6502 we determined a white dwarf velocity semiamplitude of KWD = 18.6 ± 0.5 km sˉ¹, and with the velocity semiamplitude of the red dwarf companion (KRD = 75.2 ± 3.1 km sˉ¹), we estimate the mass ratio to be q = 0.25 ± 0.01. Adopting a spectroscopic mass determination for the white dwarf, we infer a low secondary mass of M RD = 0.14 ± 0.01 M⊙. For EUVE J2013+400 we determine a white dwarf velocity semiamplitude of KWD = 36.7 ± 0.7 km sˉ¹. The FUSE observations of EUVE J0720-317 cover approximately 30% of the binary period and, combined with the HSTGHRS measurements, we update the binary properties. FUSE observations of Feige 24 cover approximately 60% of the orbit, and we combine this data set with HST STIS data to update the binary properties.

DOI

10.1086/526411

Publication Date

3-10-2008

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