AAS 202nd Meeting, May 2003
Session 13 Stars and Supernovae
Oral, Monday, May 26, 2003, 10:00-11:30am, 204

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[13.02D] Nonlinear time series analysis of PG1351+489 light intensity curves

N. Jevtic, J.S. Schweitzer (University of Connecticut)

A nonlinear time series analysis is performed on light intensity data for variable DB white dwarf PG 1351+489. The data were collected and reduced using a spectral window by the WET during its xCov12 campaign. Two data sets were analyzed: one integrated to 30 s and the other to 10 s. The latter was obtained by Antonio Kanaan (of the Brazilian National Observatory in Itajuba), at the 82" telescope at McDonald Observatory in Texas.

The light intensity curves of PG 1351+489 result in a power spectrum with a dominant fundamental frequency and its nonlinearly generated harmonics on a broadband background and other lower amplitude lines. Our time delay phase space portrait of this star in three dimensions is a rhomboidal shape wrapped around a torus. Its two dimensional projections are triangular. This differs from earlier reports of a more circular two dimensional representation. We show that the difference is due to binning to 80 s and the filtering of data in the earlier work. A circular phase space portrait may be obtained if only the fundamental frequency is used and the reconstruction grows in complexity as more and more of the power spectrum is included.

We also obtained the Poincare sections for the phase space portraits of PG 1351+489 for both the 30 s and 10 s binned data. For the 30 s integrated data, the only observed Poincare section return times correspond to the fundamental frequency. For the 10 s integrated data, other return times are observed. We propose dynamical resetting as the cause. We give an example of dynamical resetting on a theoretical model.

Nonlinear projective filtering of the 30 s binned data resulted in ~40 times lower white noise. As a result, we were able to identify two additional harmonics of the fundamental frequency (with one more tentative harmonic identification). Three additional lines at multiples of half the fundamental frequency are observed and at least three other nonlinearly generated lines are also visible.

The author(s) of this abstract have provided an email address for comments about the abstract: JevticNada@aol.com

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.