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Institut für Astronomie und Astrophysik

Abteilung Astronomie

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Preprint 14/02

The rotational velocity of the sdOB primary of the eclipsing binary system LB3459 (AA DOR)

T. Rauch (1,2), K. Werner (1)

(1) Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Sand 1, D-72076 Tübingen, Germany
(2) Dr.-Remeis-Sternwarte, Bamberg, Germany

To appear in: Astronomy & Astrophysics

Abstract. We present an analysis of the rotational velocity of the primary of LB3459 based on 107 new high-resolution and high-S/N ESO VLT UVES spectra. 105 of them cover a complete orbital period (0.26d) of this binary system. We have determined an orbital period of P=22600.702 ±0.005 sec, a radial velocity amplitude of A1=39.19 ±0.05 km/sec, and T0 = 2451917.152690 ±0.000005. From simulations of the He II 4686Å line profile (based on NLTE model atmosphere calculations), we derive vrot = 47 ±5 km/sec.
We present an animation which shows the orbital movement of the binary system, its synthetic lightcurve, and compares the phase-dependent variation of the predicted with the observed He II 4686Å line profile.
The radius of the cool component is almost the same size like Jupiter but its mass is about 70 times higher than Jupiter's mass. Thus, from its present mass (M2 = 0.066 Msol), the secondary of LB3459 lies formally within the brown-dwarf mass range (0.013 - 0.08 Msol). It might be a former planet which has survived the previous common-envelope phase and even has gained mass.

Key words: -

Paper (366k gzip'ed Postscript including figures)

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