Institut für Astronomie und Astrophysik
Abteilung AstronomieSand 1, D-72076 Tübingen, Germany
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Stefan Klepp, Thomas Rauch
Institute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, Eberhard Karls University, Tuebingen, Germany
To be published in: A&A
Abstract. AA Dor is an eclipsing, post common-envelope binary with an sdOB-type primary and a low-mass secondary. Eleven years ago, an NLTE spectral analysis showed a discrepancy in the surface gravity that was derived by radial-velocity and light-curve analysis, log g = 5.21 ± 0.1 (cm/sec2) and log g = 5.53 ± 0.03, respectively.
We aim to determine both the effective temperature and surface gravity of AA Dor precisely from high-resolution, high-S/N observations taken during the occultation of the secondary.
We calculated an extended grid of metal-line blanketed, state-of-the-art, non-LTE model atmospheres in the parameter range of the primary of AA Dor. Synthetic spectra calculated from this grid were compared to optical observations. We verify Teff = 42000 ± 1000 K from our former analyses and determine a higher log g = 5.46 ± 0.05. The main reason are new Stark-broadening tables that were used for calculating of the theoretical Balmer-line profiles. Our result for the surface gravity agrees with the value from light-curve analysis within the error limits, thereby solving the so-called gravity problem in AA Dor.
Preprint (325 kb PDF file including figures)
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Last modified 08 Jun 2011