2019MNRAS.482..758S

The driving mechanism responsible for exciting g-mode pulsations in the helium-rich hot subdwarf LS IV-14°116 has, so far, proved elusive. To date, only the ε-mechanism has offered a partial solution. We demonstrate that models of carbon-enhanced helium main-sequence stars having a mass of 0.5 M_☉ are unstable to g-mode pulsations in exactly the right period range to match the observations, and that these pulsations are excited by the κ-mechanism driven by carbon- and oxygen opacity bumps at around 10⁶ K. Helium-rich hot subdwarf pulsators therefore represent a low-temperature extension of the GW Vir variables. The required carbon enrichment can be explained if rapid mass-loss from a 2 M_☉ helium star occurs after core helium has been substantially depleted, presumably as a consequence of some binary interaction.