2010ApJ...718L..97V

We present a seismic analysis of the pulsating hot B subdwarf KPD 1943+4058 (KIC 005807616) on the basis of the long-period, gravity-mode pulsations recently uncovered by Kepler. This is the first time that g-mode seismology can be exploited quantitatively for stars on the extreme horizontal branch, all previous successful seismic analyses having been confined so far to short-period, p-mode pulsators. We demonstrate that current models of hot B subdwarfs can quite well explain the observed g-mode periods, while being consistent with independent constraints provided by spectroscopy. We identify the 18 pulsations retained in our analysis as low-degree (ℓ = 1 and 2), intermediate-order (k = -9 through -58) g-modes. The periods (frequencies) are recovered, on average, at the 0.22% level, which is comparable to the best results obtained for p-mode pulsators. We infer the following structural and core parameters for KPD 1943+4058 (formal fitting uncertainties only): T_eff= 28,050 ± 470 K, log g = 5.52±0.03, M_*= 0.496±0.002 M_☉, log (M_env/M _*) = -2.55±0.07, log (1 - M_core/M_*) = -0.37±0.01, and X_core(C+O) = 0.261±0.008. We additionally derive the age of the star since the zero-age extended horizontal branch 18.4±1.0 Myr, the radius R = 0.203±0.007 R _☉, the luminosity L = 22.9±3.13 L_☉, the absolute magnitude M_V= 4.21±0.11, the reddening index E(B - V) = 0.094±0.017, and the distance d = 1180±95 pc.