Hubble space telescope fos spectroscopy of the ultrashort-period dwarf nova WZ Sagittae: The underlying degenerate

Edward M. Sion, F. H. Cheng, Knox S. Long, Paula Szkody, Ron L. Gilliland, Min Huang, Ivan - Hubeny

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

Two consecutive Hubble Space Telescope Faint Object Spectrograph (FOS) spectra of the exposed white dwarf in the ultrashort-period, high-amplitude, dwarf nova WZ Sge, reveal a rich absorption line spectrum of neutral carbon and ionized metals, the Stark-broadened Lyα absorption wing, the H2 quasi-molecular Lyα "satellite" absorption line, and a double-peaked C IV emission line which is variable with orbital phase. A synthetic spectral analysis of the white dwarf yields Teff = 14,900 K ± 250 K, log g = 8.0. In order to fit the strongest C I absorption lines and account for the weakness of the silicon absorption lines, the abundance of carbon in the photosphere must be ∼0.5 solar, silicon abundance is 5 × 10-3 solar, with all other metal species appearing to be 0.1-0.001 times solar. The H2 quasi-molecular absorption is fitted very successfully. The photospheric metals have diffusion timescales of fractions of a year, and thus they must have been accreted long after the 1978 December outburst. The source of the most abundant metal, carbon, is considered. If the time-averaged accretion rate during quiescence is low enough for diffusive equilibrium to prevail, then the equilibrium accretion rate of neutral carbon is 7 × 10-16 M yr-1. A convective dredge-up origin for the concentration of carbon is extremely unlikely, given that the white dwarf atmosphere is H-rich while in single degenerates showing carbon and hydrogen, the C and H are trace elements in a helium background. Additional implications are explored.

Original languageEnglish (US)
Pages (from-to)957-962
Number of pages6
JournalAstrophysical Journal
Volume439
Issue number2
StatePublished - Feb 1 1995
Externally publishedYes

Fingerprint

Hubble Space Telescope
spectroscopy
carbon
metal
metals
silicon
accretion
molecular absorption
faint objects
dredger
photosphere
trace elements
outburst
wings
spectral analysis
helium
spectrographs
spectrum analysis
line spectra
trace element

Keywords

  • Novae, cataclysmic variables
  • Stars: individual (WZ Sagittae)
  • Ultraviolet: stars
  • White dwarfs

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Sion, E. M., Cheng, F. H., Long, K. S., Szkody, P., Gilliland, R. L., Huang, M., & Hubeny, I. . (1995). Hubble space telescope fos spectroscopy of the ultrashort-period dwarf nova WZ Sagittae: The underlying degenerate. Astrophysical Journal, 439(2), 957-962.

Hubble space telescope fos spectroscopy of the ultrashort-period dwarf nova WZ Sagittae : The underlying degenerate. / Sion, Edward M.; Cheng, F. H.; Long, Knox S.; Szkody, Paula; Gilliland, Ron L.; Huang, Min; Hubeny, Ivan -.

In: Astrophysical Journal, Vol. 439, No. 2, 01.02.1995, p. 957-962.

Research output: Contribution to journalArticle

Sion, EM, Cheng, FH, Long, KS, Szkody, P, Gilliland, RL, Huang, M & Hubeny, I 1995, 'Hubble space telescope fos spectroscopy of the ultrashort-period dwarf nova WZ Sagittae: The underlying degenerate', Astrophysical Journal, vol. 439, no. 2, pp. 957-962.
Sion EM, Cheng FH, Long KS, Szkody P, Gilliland RL, Huang M et al. Hubble space telescope fos spectroscopy of the ultrashort-period dwarf nova WZ Sagittae: The underlying degenerate. Astrophysical Journal. 1995 Feb 1;439(2):957-962.
Sion, Edward M. ; Cheng, F. H. ; Long, Knox S. ; Szkody, Paula ; Gilliland, Ron L. ; Huang, Min ; Hubeny, Ivan -. / Hubble space telescope fos spectroscopy of the ultrashort-period dwarf nova WZ Sagittae : The underlying degenerate. In: Astrophysical Journal. 1995 ; Vol. 439, No. 2. pp. 957-962.
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