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The occurrence of non-pulsating stars in the γ Dor and δ Sct instability regions

Published online by Cambridge University Press:  18 February 2014

Joyce A. Guzik
Affiliation:
Los Alamos National Laboratory MS T086, Los Alamos, NM 87545USA email: joy@lanl.gov, pbradley@lanl.gov
Paul A. Bradley
Affiliation:
Los Alamos National Laboratory MS T086, Los Alamos, NM 87545USA email: joy@lanl.gov, pbradley@lanl.gov
Jason Jackiewicz
Affiliation:
Dept. of Astronomy, New Mexico State University P.O. Box 30001, MSC 4500, Las Cruces, NM 88003USA email: jasonj@nmsu.edu
Katrien Uytterhoeven
Affiliation:
Instituto de Astrofísica de Canarias (IAC), 38200, La Laguna, Tenerife, Spain Departamento de Astrofísica, Universidad de La Laguna, 38200 La Laguna, Tenerife, Spain email: katrien@iac.es
Karen Kinemuchi
Affiliation:
Apache Point Observatory P.O. Box 59, 2001 Apache Point Road, Sunspot, NM 88349USA email: kinemuchi@apo.nmsu.edu
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Abstract

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We examine the light curves of over 2700 stars observed in long cadence by the Kepler spacecraft as part of the Guest Observer program. Most of these stars are faint (Kepler magnitude > 14), and fall near or within the effective temperature and log g range of the γ Dor and δ Sct instability strips. We find that the pulsating stars are obvious from inspection of the light curves and power spectra, even for these faint stars. However, we find that a large number of stars are ‘constant’, i.e. show no frequencies in the 0.2 to 24 d−1 range above the 20 ppm level. We discuss the statistics for the constant stars, and some possible physical reasons for lack of pulsations. On the other hand, γ Dor and δ Sct candidates have been found in the Kepler data spread throughout and even outside of the instability regions of both types that were established from pre-Kepler ground-based observations. We revisit mechanisms to produce g- or p-mode pulsations in conditions when these modes are not expected to be unstable via the He-ionization κ effect (δ Sct) or convective blocking (γ Dor) pulsation driving mechanisms.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2014 

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