Early Asteroseismic Results from Kepler: Structural and Core Parameters of the Hot B Subdwarf KPD 1943+4058 as Inferred from g-mode Oscillations

Details Early Asteroseismic Results from Kepler: Structural and Core Parameters of the Hot B Subdwarf KPD 1943+4058 as Inferred from g-mode Oscillations Early Asteroseismic Results from Kepler: Structural and Core Parameters of the Hot B Subdwarf KPD 1943+4058 as Inferred from g-mode Oscillations

Aug 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010apj...718l..97v&link_type=abstract

The Astrophysical Journal Letters, Volume 718, Issue 2, pp. L97-L101 (2010).

Astronomy and Astrophysics

Astronomy

25

Stars: Individual: Kpd 1943+4058, Stars: Interiors, Stars: Oscillations, Subdwarfs

Scientific paper

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 (ell = 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 sun, 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 sun, the luminosity L = 22.9 ± 3.13 L sun, 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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