An evolutionary channel for CO-rich and pulsating He-rich subdwarfs

Recently a new class of hot subluminous stars strongly enriched in C and O have been discovered (CO-sdOs). These show abundances very similar to those observed PG1159 but at lower temperatures. Moreover, it has recently suggested that enrichment might be the key ingredient driving pulsations He-rich subdwarf (He-sdBVs). Here we argue these two types rare can explained by variant one main channels forming stars. The scenario involves formation merging He-core white dwarf less massive CO-core dwarf. We constructed simple merger models computed their subsequent evolution. products are agreement with surface parameters composition CO-sdOs. In addition, performed simulations including effects element diffusion excitation pulsations. form stellar structures parameters, abundances, pulsation periods displayed He-sdBVs. conclude proposed scenario, or some it, offers plausible explanation for CO-sdOs, pulsating He-sdBs low-luminosity