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| Paper: |
Recent Investigations on AA Doradus |
| Volume: |
452, Fifth Meeting on Hot Subdwarf Stars and Related Objects |
| Page: |
111 |
| Authors: |
Rauch, T. |
| Abstract: |
AA Dor is an eclipsing, post common-envelope binary with an
sdOB-type primary and an unseen low-mass secondary, believed to
be a brown dwarf. Eleven years ago, a NLTE spectral analysis
of the primary showed a discrepancy with the surface gravity
that was derived by radial-velocity and light-curve analysis
that could not be explained.
Since then, emission lines of the secondary were identified in
optical spectra and its orbital-velocity amplitude was measured.
Thus, the masses of both components are known, however, within
relatively large error ranges. The secondary's mass was found
to be around the stellar hydrogen-burning mass limit and, thus,
it may be a brown dwarf or a late M-type dwarf. In addition, a
precise determination of the primary's rotational velocity
showed recently, that it rotates at about 65% of bound
rotation—much slower than previously assumed.
A new spectral analysis by means of metal-line blanketed,
state-of-the-art, non-LTE model atmospheres solves the so-called
gravity problem in AA Dor—our result for the surface gravity
is, within the error limits, in agreement with the value from
light-curve analysis.
We present details of our recent investigations on AA Dor. |
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