FUSE determination of the abundances of iron-peak elements in the PG 1716+426 stars

We present preliminary analysis of the FUSE spectra of five PG1716+426 stars, the subgroup of sdB stars that exhibit very low amplitude, long-period multiperiodic luminosity variations. Our aim is to investigate whether these stars display abundances of iron-peak elements which differ from those observed in the shorter-period EC 14026 stars and in non-variable sdB stars. Our preliminary results suggest that the abundances of Fe, Mn, Co and Ni in PG 1716+426 stars do not differ appreciably from those measured in our reference samples. The implications of these findings for non-adiabatic calculations which link the driving of both the long- and short-period pulsations to an opacity bump associated with a local enhancement of the abundance of iron and iron-peak elements in the envelope are briefly discussed.