Bibcode
Breger, M.; Balona, L.; Lenz, P.; Hollek, J. K.; Kurtz, D. W.; Catanzaro, G.; Marconi, M.; Pamyatnykh, A. A.; Smalley, B.; Suárez, J. C.; Szabo, R.; Uytterhoeven, K.; Ripepi, V.; Christensen-Dalsgaard, J.; Kjeldsen, H.; Fanelli, M. N.; Ibrahim, K. A.; Uddin, K.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 414, Issue 2, pp. 1721-1731.
Advertised on:
6
2011
Citations
64
Refereed citations
51
Description
In the faint star KIC 9700322 observed by the Kepler satellite, 76
frequencies with amplitudes from 14 to 29 000 ppm were detected. The two
dominant frequencies at 9.79 and 12.57 d-1 (113.3 and 145.5
μHz), interpreted to be radial modes, are accompanied by a large
number of combination frequencies. A small additional modulation with a
0.16 d-1 frequency is also seen; this is interpreted to be
the rotation frequency of the star. The corresponding prediction of slow
rotation is confirmed by a spectrum from which v sin i= 19 ± 1 km
s-1 is obtained. The analysis of the spectrum shows that the
star is one of the coolest δ Sct variables. We also determine
Teff = 6700 ± 100 K and log g = 3.7 ± 0.1,
compatible with the observed frequencies of the radial modes. Normal
solar abundances are found. An ℓ= 2 frequency quintuplet is also
detected with a frequency separation consistent with predictions from
the measured rotation rate. A remarkable result is the absence of
additional independent frequencies down to an amplitude limit near 14
ppm, suggesting that the star is stable against most forms of non-radial
pulsation. A low-frequency peak at 2.7763 d-1 in KIC 9700322
is the frequency difference between the two dominant modes and is
repeated over and over in various frequency combinations involving the
two dominant modes. The relative phases of the combination frequencies
show a strong correlation with frequency, but the physical significance
of this result is not clear. Based on observations obtained with the
Hobby-Eberly Telescope, which is a joint project of the University of
Texas at Austin, the Pennsylvania State University, Stanford University,
Ludwig-Maximilians-Universität München and
Georg-August-Universität Göttingen.