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 lowdegree (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 (Menv/M*) = -2.55 ±0.07, log (1 - Mcore/M*) = -0.37±0.01, and Xcore(C+O)=0.261±0.008.We additionally derive the age of the star since the zero-age extended horizontal branch 18.4±1.0Myr, the radius R=0.203±0.007R⊙, the luminosity L=22.9±3.13 L⊙, the absolute magnitude MV = 4.21 ±0.11, the reddening index E(B -V ) = 0.094 ±0.017, and the distance d = 1180 ±95 pc.
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ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science
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Van Grootel, G. V. (Creator), Charpinet, S. (Creator), Fontaine, G. (Creator), Brassard, P. (Creator), Green, E. M. (Creator), Randall, S. K. (Creator), Silvotti, R. (Creator), Østensen, R. H. (Contributor), Kjeldsen, H. (Creator), Christensen-Dalsgaard, J. (Creator), Borucki, W. J. (Creator), Koch, D. (Creator), Charpinet, S. (Creator), Fontaine, G. (Creator), Silvotti, R. (Creator) & Kjeldsen, H. (Creator), Centre de Donnees Strasbourg (CDS), 2012