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J/ApJ/718/L97     Early asteroseismic results from Kepler   (Van Grootel+, 2010)

Early asteroseismic results from Kepler: structural and core parameters of the hot b subdwarf KPD 1943+4058 as inferred from g-mode oscillations. Van Grootel V., Charpinet S., Fontaine G., Brassard P., Green E.M., Randall S.K., Silvotti R., Ostensen R.H., Kjeldsen H., Christensen-Dalsgaard J., Borucki W.J., Koch D. <Astrophys. J., 718, L97-L101 (2010)> =2010ApJ...718L..97V
ADC_Keywords: Stars, B-type ; Stars, variable Keywords: stars: individual (KPD 1943+4058) - stars: interiors - stars: oscillations - subdwarfs Abstract: 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): Teff=28050±470K, logg=5.52±0.03, M*=0.496±0.002M, log(Menv/M*)=-2.55±0.07, log(1-Mcore/M*)=-0.3±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±3.13L, the absolute magnitude MV=4.21±0.11, the reddening index E(B-V)=0.094±0.017, and the distance d=1180±95pc. Description: In this Letter, we exploit the exceptional data obtained on KPD 1943+4058 by Kepler. We also obtained a low-resolution (9Å), moderately high S/N (∼112 in the blue) spectrum of KPD 1943+4058 with the Steward Observatory 2.3m Bok Telescope on 2008 12 June. Objects: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 19 45 25.48 +41 05 33.8 KIC 005807616 = KPD 1943+4058 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 50 35 List of frequencies fn (n is by order of decreasing amplitude) detected in KPD 1943+4058 table2.dat 80 79 Mode identification and other properties
See also: J/A+A/525/A23 : Frequency analysis of HD 49434 (Mathias+, 2011) J/A+A/506/471 : Frequency analysis of CoRoT B stars (Degroote+, 2009) J/A+A/506/111 : Frequency analysis of HD 180642 (V1449 Aql) (Degroote+, 2009) J/A+A/506/79 : Asteroseismic analysis of HD 174936 (Garcia Hernandez+, 2009) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 5 A5 --- ID Mode identification (f1-f27, u1-u14) 7 A1 --- f_ID [*] *: pulsation period safely assumed to be independent (18 periods used in the analysis) 9- 15 F7.2 s Per Period 17- 23 F7.3 uHz Freq Frequency 25- 28 F4.1 --- S/N Signal to noise ratio 30- 50 A21 --- Comm Comments
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1 I1 --- l [1/4] Degree 3- 5 I3 --- k [-63/-3] Radial order 7- 13 F7.3 uHz nuObs ? Observed frequency 15- 22 F8.3 uHz nuTh Theoretical frequency 24- 30 F7.2 s PObs ? Observed period 32- 38 F7.2 s PTh Theoretical period 40- 45 F6.3 [10-7J] logE Log of the energy; in erg 47- 52 F6.4 --- Ckl Ledoux coefficient 54- 58 F5.2 % DelX/X ? Relative dispersion (on P or ν) 60- 65 F6.2 s DelP ? Period dispersion ΔP 67- 72 F6.3 uHz Delnu ? Frequency dispersion Δν 74- 78 A5 --- ID Mode identification (f1-f27, u1-u14) 80 A1 --- f_ID [1/2] Flag on ID (1)
Note (1): Flag as follows: 1 = Additional frequencies (see Table 1; un). 2 = Left-aside frequencies (see section 3.2 and Table 1).
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 08-Jun-2012
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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