A search for O VI in the winds of B-type stars

Astronomy and Astrophysics (Impact Factor: 4.38). 05/2003; 405(3). DOI: 10.1051/0004-6361:20030601
Source: arXiv


We have conducted a survey of FUSE spectra of 235 Galactic B-type stars in order to determine the boundaries in the H-R diagram for the production of the superion O VI in their winds. By comparing the locations and morphology of otherwise unidentified absorption features in the vicinity of the O VI resonance doublet with the bona fide wind profiles seen in archival IUE spectra of the resonance lines of N V, Si IV and C IV, we were able to detect blueshifted O VI lines in the spectra of giant and supergiant stars with temperature classes as late as B1. No features attributable to O VI were detected in dwarfs later than B0, or in stars of any luminosity class later than B1, although our ability to recognize weak absorption features in these stars is severely restricted by blending with photospheric and interstellar features. We discuss evidence that the ratio of the ion fractions of O VI and N V is substantially different in the winds of early B-type stars than O-type stars. Comment: Accepted for publication in the A&A

Download full-text


Available from: Nicolas Lehner, Nov 21, 2013
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present Far Ultraviolet Spectroscopic Explorer (FUSE) data on O VI absorption lines observed toward nine stars behind the Vela supernova remnant (SNR). The O VI observations are compared with International Ultraviolet Explorer (IUE) observations of C IV absorption toward the same stars. All of these stars are B stars, which generally have complex continua, making the extraction of absorption lines difficult. However, four of the stars, HD 72088, HD 72089, HD 72350, and HD 72537, are rapid rotators (v sin i 150 km s-1), making the derivation of absorption column densities much easier. We present O VI and C IV column densities for the "main component" (i.e., the low-velocity component) for these stars. In the FUSE spectra of three of the rapid rotators (HD 72088, HD 72089, and HD 72537) we find high-velocity components of O VI at ~150 km s-1 that we attribute to the SNR shock. HD 72350 has very strong H2 absorption, which obscures any possible high-velocity O VI absorption. To detect the high-velocity O VI absorption in HD 72088 requires employing a technique for removing the H2 line at 1032.35 Å (121.6 km s-1 relative to O VI). The O VI data are consistent with steady radiative shock models with vs ≈ 150 km s-1, but we do not detect C IV at the same velocities. Instead we find high-velocity C IV at lower velocities (~100 km s-1). We discuss the implications of our results for models of the evolution of the Vela SNR.
    The Astrophysical Journal 12/2008; 606(2):900. DOI:10.1086/383135 · 5.99 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The results of detailed level-by-level calculations of Auger and radiative cascades after K-vacancy production are presented for the astrophysically important elements Ne, Mg, Si, S and Ar. Calculations are performed in the single-configuration quasi-relativistic approximation. The whole isonuclear sequence of ions for a given element is considered. For the first time dependence of cascade on the initial vacancy state is investigated. The populations are presented not only for the levels of final configurations, but also for the levels ofexcited configurations after the Auger transitions. An intense characteristic emission can be observed from such levels.
    The Astrophysical Journal 05/2012; 750. DOI:10.1088/0004-637X/750/2/90 · 5.99 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The results of Auger and radiative cascades after the production of a vacancy in the K-shell and the additional ionization or excitation of the other shell are presented for the various ions of astrophysically important elements, namely Ne, Mg, Si, S, and Ar. The detailed level-by-level calculations are performed using the single-configuration quasi-relativistic approximation. The populations for the levels of the excited configurations produced during cascade as well as for the final ions are presented. These data enable one to take into account two-electron processes at the K-shell ionization and thus to supplement the results of our earlier investigation for the K-vacancy cascades.
    The Astrophysical Journal 08/2015; 810:26(1). DOI:10.1088/0004-637X/810/1/26 · 5.99 Impact Factor