摘要：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. Based on a photometric and preliminary asteroseismic analysis, we
show that the mid B-type giant 18 Peg is one of the most evolved members of the rare class
of slowly pulsating B-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 orbit that is greater than
6 years. Further spectroscopic and photometric monitoring and a sophisticated
asteroseismic investigation are required to exploit the full potential of this star as a
benchmark object for stellar evolution theory.
