The evolved slowly pulsating B star 18 Peg
A testbed for upper main sequence stellar evolution
1 Dr. Karl Remeis-Observatory & ECAP, Astronomical Institute, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Sternwartstr. 7, 96049 Bamberg, Germany
2 Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium
3 Instituut voor Sterrenkunde, KULeuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
Published online: 8 September 2017
The predicted width of the upper main sequence in stellar evolution models depends on the empirical calibration of the convective overshooting parameter. Despite decades of discussions, its precise value is still unknown and further observational constraints are required to gauge it. Irrgang et al. () showed that the B3 III giant 18 Peg is one of the most evolved members of the class of slowly pulsating B (SPB) stars and, thus, bears tremendous potential to derive a tight lower limit for the width of the upper main sequence. In addition, 18 Peg turns out to be part of a single-lined spectroscopic binary system with an eccentric, more than 6-year orbit. The orbital solution, in combination with the absence of additional signatures of the secondary component in the spectroscopic data and the spectral energy distribution, lead to the conclusion that all the observations of 18 Peg are fully compatible with the assumption that the secondary component is either a main-sequence star with a mass of 1-4 M⊙ or a neutron star.
© The Authors, published by EDP Sciences, 2017
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.