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Title: Kepler and the long-period variables

High-precision Kepler photometry is used to explore the details of asymptotic giant branch (AGB) light curves. Since AGB variability has a typical timescale on the order of a year, we discuss at length the removal of long-term trends and quarterly changes in Kepler data. Photometry for a small sample of nine semi-regular (SR) AGB stars is examined using a 30 minute cadence over a period of 45 months. While undergoing long-period variations of many magnitudes, the light curves are shown to be smooth at the millimagnitude level over much shorter time intervals. No flares or other rapid events were detected on a sub-day timescale. The shortest AGB period detected is on the order of 100 days. All the SR variables in our sample are shown to have multiple modes. This is always the first overtone, typically combined with the fundamental. A second common characteristic of SR variables is shown to be the simultaneous excitation of multiple closely separated periods for the same overtone mode. Approximately half the sample had a much longer variation in the light curve, likely a long secondary period (LSP). The light curves were all well represented by a combination of sinusoids. However, the properties of themore » sinusoids are time variable, with irregular variations present at low levels. No non-radial pulsations were detected. It is argued that the LSP variation seen in many SR variables is intrinsic to the star and linked to multiple mode pulsation.« less
Authors:
;  [1] ;  [2] ; ;  [3] ;  [4]
  1. University of Vienna, Department of Astrophysics, T├╝rkenschanzstrasse 17, A-1180 Vienna (Austria)
  2. Department of Biological and Physical Sciences, South Carolina State University, P.O. Box 7024, Orangeburg, SC 29117 (United States)
  3. National Optical Astronomy Observatories, P.O. Box 26732, Tucson, AZ 85726 (United States)
  4. Department of Biological and Physical Sciences, South Carolina State University, P.O. Box 7296, Orangeburg, SC 29117 (United States)
Publication Date:
OSTI Identifier:
22342206
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (New York, N.Y. Online); Journal Volume: 148; Journal Issue: 6; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCURACY; APPROXIMATIONS; ASYMPTOTIC SOLUTIONS; DATA ANALYSIS; EXCITATION; PHOTOMETRY; PULSATIONS; STARS; VISIBLE RADIATION