Journal Article

First <i>Kepler</i> results on compact pulsators – VII. Pulsating subdwarf B stars detected in the second half of the survey phase

A. S. Baran, S. D. Kawaler, M. D. Reed, A. C. Quint, S. J. O'Toole, R. H. Østensen, J. H. Telting, R. Silvotti, S. Charpinet, J. Christensen-Dalsgaard, M. Still, J. R. Hall and K. Uddin

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 4, pages 2871-2884
Published in print July 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI:
First Kepler results on compact pulsators – VII. Pulsating subdwarf B stars detected in the second half of the survey phase

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We present five new pulsating subdwarf B (sdB) stars discovered by the Kepler spacecraft during the asteroseismology survey phase. We perform time series analysis on the nearly continuous month-long Kepler data sets of these five objects; these data sets provide nearly alias-free time series photometry at unprecedented precision. Following an iterative pre-whitening process, we derive the pulsational frequency spectra of these stars, separating out artefacts of known instrumental origin. We find that these new pulsating sdB stars are multiperiodic long-period pulsators of the V1093 Her type, with the number of periodicities ranging from eight (KIC 8302197) to 53 (KIC 11558725). The frequencies and amplitudes are typical of g-mode pulsators of this type. We do not find any evidence for binarity in the five stars from their observed pulsation frequencies. As these are g-mode pulsators, we briefly looked for period spacings for mode identification and found average spacings of about 260 and 145 s. This may indicate l= 1 and 2 patterns. Some modes may show evidence of rotational splitting. These discoveries complete the list of compact pulsators found in the survey phase. Of the 13 compact pulsators, only one star was identified as a short-period (p-mode) V361 Hya pulsator, while all other new pulsators turned out to be V1093 Her class objects. Among the latter objects, two of them seemed to be pure V1093 Her while the others show additional low-amplitude peaks in the p-mode frequency range, suggesting their hybrid nature. Authenticity of these peaks will be tested with longer runs currently under analysis.

Keywords: asteroseismology; space vehicles; stars: oscillations; techniques: photometric; subdwarfs

Journal Article.  7350 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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