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Post Info TOPIC: EC 14012-1446
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RE: EC 14012-1446
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Title: Asteroseismology of DAV star EC14012-1446, mode identification and model fittings
Author: Yanhui Chen, Yan Li

EC14012-1446 was observed by Handler et al. in April 2004, June 2004, May 2005, and April 2007, and by Provencal et al. in 2008. We review the observations together and obtain 34 independent frequencies. According to the frequency splitting and the asymptotic period spacing law, we identify 6 l=1 modes, 4 l=2 modes, 5 l=3 modes, 10 l=1 or 2 modes. Grids of white dwarf models are generated by WDEC with H, He, C, O diffusion in a four-parameter space. The core compositions are directly from white dwarf models generated by MESA. The best-fitting model has M*=0.710\,solar mass, Teff=12200\,K, log(MHe/M*)=-2.5, log(MH/M*)=-7.0, log\,g=8.261, and \phi=3.185\,s. There are 4, 2, and 1 modes identified as trapped in H envelope for observed l=1, 2, and 3 modes, respectively. Trapped modes jump the queue of uniform period spacing.

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Title: The pulsating DA white dwarf star EC 14012-1446: results from four epochs of time-resolved photometry
Authors: G. Handler, E. Romero-Colmenero, J. L. Provencal, K. Sanchawala, M. A. Wood, I. Silver, W.-P. Chen

The pulsating DA white dwarfs are the coolest degenerate stars that undergo self-driven oscillations. Understanding their interior structure will help to understand the previous evolution of the star. To this end, we report the analysis of more than 200 h of time-resolved CCD photometry of the pulsating DA white dwarf star EC 14012-1446 acquired during four observing epochs in three different years, including a coordinated three-site campaign. A total of 19 independent frequencies in the star's light variations together with 148 combination signals up to fifth order could be detected. We are unable to obtain the period spacing of the normal modes and therefore a mass estimate of the star, but we infer a fairly short rotation period of 0.61 +/- 0.03 d, assuming the rotationally split modes are l=1. The pulsation modes of the star undergo amplitude and frequency variations, in the sense that modes with higher radial overtone show more pronounced variability and that amplitude changes are always accompanied by frequency variations. Most of the second-order combination frequencies detected have amplitudes that are a function of their parent mode amplitudes, but we found a few cases of possible resonantly excited modes. We point out the complications in the analysis and interpretation of data sets of pulsating white dwarfs that are affected by combination frequencies of the form f_A+f_B-f_C intruding into the frequency range of the independent modes.

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