2012ApJ...756....9J -
Astrophys. J., 756, 9 (2012/September-1)
Stochastic brightness variations in the central star of planetary nebula NGC 6826.
JEVTIC N., STINE P., NILSEN W., SCHWEITZER J.S., JENKINS J.M., KLAUS T.C., LIE J. and McCAULIFF S.
Abstract (from CDS):
One year of continuous Kepler Space Telescope data for the central object of planetary nebula NGC 6826 (KIC 12071221) were analyzed. KIC 12071221 has long-cadence light curves with stochastic brightness variations and broadband power spectra. The exception is a one-month long period during which variability was detected with a period of 14.8 hr. In search of the origin of this periodicity and in an attempt to better understand the complex NGC 6826 system, long-cadence KIC 12071221 data were analyzed using nonlinear time series methods. Nonlinear projective noise reduction from a phase-space dimension of six lowered the tail of the power spectra at the higher frequencies by factors of 38-133, an unexpected result for light curves with no obvious dominant frequencies. Even more notable is the identification of a structured distribution of trajectories, or coherence, in the reconstructed phase space for vectors spanning an interval of 1.5 hr. Organization weakens as the delay increases and is lost for phase-space vectors spanning times longer than 10 hr. This may be indicative of a binary object which shares a common envelope and/or pulsations but for a complete understanding one or both may have to be combined with wind structure. Thus, an estimate is made of the timescale of the response to what we propose is stochastic driving. This estimate of the timescale of the organized response is made by monitoring the loss of structure in the distribution of trajectories in phase space, a novel application of nonlinear methodology that may be used on data sampled with any sampling time.
Abstract Copyright:
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Journal keyword(s):
methods: data analysis - planetary nebulae: individual: NGC 6826 - stars: variables: general - telescopes
Simbad objects:
2
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