The unusual variable hot B subdwarf ls IV-14°116

We first present the results of follow-up photometric observations of the He-rich hot B subdwarf LS IV-14°116, which confirm the presence of multiperiodic luminosity variations in the light curve of this star. Rather surprisingly, no other follow-up observations of this kind seem to have been published after the initial suggestion in 2005 that LS IV-14°116 could be a pulsating star of a new kind. We were able to extract from our data at least six significant periodicities ranging from 1954s to 5084s, including the two oscillations uncovered previously. We also present the results of an analysis combining a high signal-to-noise optical spectrum of LS IV-14°116 with recently developed non-local thermodynamic equilibrium model atmospheres and synthetic spectra. Our best estimates of the atmospheric parameters of this star are T _eff = 34950 250K, log g = 5.93 0.04, and log N(He)/N(H) = -0.62 0.03 (formal fitting errors only). These place LS IV-14°116 very near the region of maximum instability in the T _eff-log g plane for short-period p-mode pulsators of the hot subdwarf type. If the luminosity variations are indeed due to pulsations, then LS IV-14°116 poses a real challenge to current theory: how can such long observed periods (which would have to be associated with medium- to high-order g-modes) be excited at such a high effective temperature and surface gravity, while the short-period p-modes, more typically excited in this domain, are not observed in this particular star?