A comprehensive near- and far-ultraviolet spectroscopic study of the hot DA white dwarf G191-B2B

Preval, S. P. and Barstow, M. A. and Holberg, J. B. and Dickinson, N. J. (2013) A comprehensive near- and far-ultraviolet spectroscopic study of the hot DA white dwarf G191-B2B. Monthly Notices of the Royal Astronomical Society, 436 (1). pp. 659-674. ISSN 0035-8711

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Abstract

We present a detailed spectroscopic analysis of the hot DA white dwarf G191-B2B, using the best signal-to-noise ratio, high-resolution near- and far-UV spectrum obtained to date. This is constructed from co-added Hubble Space Telescope (HST) Space Telescope Imaging Spectrometer (STIS) E140H, E230H and FUSE observations, covering the spectral ranges of 1150-3145Å and 910-1185 Å, respectively. With the aid of recently published atomic data, we have been able to identify previously undetected absorption features down to equivalent widths of only a few mÅ. In total, 976 absorption features have been detected to 3σ confidence or greater, with 947 of these lines now possessing an identification, the majority of which are attributed to Fe and Ni transitions. In our survey, we have also potentially identified an additional source of circumstellar material originating from Si III. While we confirm the presence of Ge detected by Vennes et al., we do not detect any other species. Furthermore, we have calculated updated abundances for C, N, O, Si, P, S, Fe and Ni, while also calculating, for the first time, a non-local thermodynamic equilibrium abundance for Al, deriving Al III/H = 1.60+0.07-0.08× 10-7. Our analysis constitutes what is the most complete spectroscopic survey of any white dwarf. All observed absorption features in the FUSE spectrum have now been identified, and relatively few remain elusive in the STIS spectrum.