An astrophysical oscillator strength for the SII 94.7 nm resonance line and S abundances in DLAs

P. Bonifacio; E. Caffau; M. Centurion; P. Molaro; G. Vladilo

doi:10.1046/j.1365-8711.2001.04495.x

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An astrophysical oscillator strength for the SII 94.7 nm resonance line and S abundances in DLAs

P. Bonifacio·E. Caffau·M. Centurion·P. Molaro·G. Vladilo

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Abstract

By using UV spectra for the O star HD 93521 taken with the ORFEUS II echelle spectrograph, we determine an ``astrophysical'' f value for the SII 94.7 nm line: f = 0.00498 (+0.00172)(-0.00138), error at 1 sigma level.This is almost a factor of 30 smaller than the guessed value found in the Kurucz database (f=0.1472), which was up to now the only one available for this transition. We use our ``astrophysical'' f to investigate the S abundance in two Damped Ly-alpha absorption systems (DLAs) observed with UVES at the ESO 8.2m Kueyen telescope. In the case of the absorber at zabs=3.02486 towards QSO 0347-3819 we find a sulphur column density which is consistent, within errors, with that determined by Centurion et al by means of the 125.9 nm line, thus providing an external check on the accuracy of our f value. For the damped absorber at zabs=4.4680 towards BR J0307-4945 we determine a high value of the S abundance, which, however, is probably the result of blending with Ly-alpha forest lines.

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P. Bonifacio, E. Caffau, M. Centurion, P. Molaro, G. Vladilo. 2001-03-15. An astrophysical oscillator strength for the SII 94.7 nm resonance line and S abundances in DLAs. https://doi.org/10.1046/j.1365-8711.2001.04495.x

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