Abstract
Aims. We present an unbiased orbit solution and mass determination of the components of the eclipsing binary <ASTROBJ>PG 1336-018</ASTROBJ> as a critical test for the formation scenarios of subdwarf B stars. Methods: We obtained high-resolution time series VLT/UVES spectra and high-speed multicolour VLT/ULTRACAM photometric observations of <ASTROBJ>PG 1336-018</ASTROBJ>, a rapidly pulsating subdwarf B star in a short period eclipsing binary. Results: Combining the radial velocity curve obtained from the VLT/UVES spectra with the VLT/ULTRACAM multicolour lightcurves, we determined numerical orbital solutions for this eclipsing binary. Due to the large number of free parameters and their strong correlations, no unique solution could be found, only families of solutions. We present three solutions of equal statistical significance, two of which are compatible with the primary having gone through a core He-flash and a common-envelope phase described by the alpha-formalism. These two models have an sdB primary of 0.466 {M<SUB>o</SUB>} and 0.389 {M<SUB>o</SUB>}, respectively. Finally, we report the detection of the Rossiter-McLaughlin effect for <ASTROBJ>PG 1336-018</ASTROBJ>. Based on observations collected at the European Southern Observatory, Chile. Program ID: 075.D-0174.
