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| Paper: |
NLTE Analysis of the Hot sdO Star Bd+28°4211: The UV Spectrum |
| Volume: |
481, 6th Meeting on Hot Subdwarf Stars and Related Objects |
| Page: |
67 |
| Authors: |
Latour, M.; Fontaine, G.; Chayer, P.; Brassard, P.; Green, E. |
| Abstract: |
We present a detailed analysis of the UV spectrum of the calibration star BD+28°4211 using high-quality spectra obtained with the HST and FUSE satellites. To this aim, we compare quantitatively the observed data with model spectra obtained from state-of-the-art non-LTE metal line-blanketed model atmospheres and synthetic spectra calculated with TLUSTY and SYNSPEC. We thus determine in a self-consistent way the abundances of 11 elements with well-defined lines in the UV. The derived abundances range from about solar to 1/10 solar and the overall quality of the derived spectral fits is very satisfying. Our analysis can be used to constrain rather tightly the effective temperature of BD+28°4211 to a value of Teff = 82,000±5000 K. We also estimate conservatively that its surface gravity falls in the range log g = 6.2–0.1+0.3. Assuming that the Hipparcos measurement for BD+28°4211 is fully reliable and that our model atmospheres are reasonably realistic, we can reconcile our spectroscopic constraints with the available parallax measurement only if the mass of BD+28°4211 is significantly less than the canonical value of 0.5 M☉ for a representative post-EHB star. |
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