Abstract
Most pulsating white dwarf stars pulsate with many periods, each of which is a probe of their interior, which has made asteroseismolgy of these stars an active field. However, disentangling the multiple periodicities requires long, uninterrupted strings of data. We briefly describe the history of multi-site observing campaigns that culminated in the development of the Whole Earth Telescope in the late 1980s that still functions today. Through examples from the May 1990 campaign on GD 358, we show how critical it is to eliminate periodic gaps in data to greatly reduce aliasing in Fourier Transforms normally used to analyze the frequency content of pulsating white dwarfs. We close with a brief description of space satellite-based data, along with the advantages and disadvantages of these data compared to ground-based data.
Highlights
White dwarf stars are the most common endpoint of stellar evolution and are the ultimate fate of all stars with masses less than about 8–10 Mo (Woosley and Heger, 2015)
We refer the reader to Winget et al (1994) for the definitive data analysis; our aim here is to graphically illustrate that the WET achieved the goal of nearly eliminating alias peaks and making asteroseismology of white dwarf stars possible
We have shown that multi-site data with 24 h coverage at some point during an observing run can drastically reduce the 1 cycle/ day alias pattern seen in Fourier Transform (FT) of pulsating white dwarfs, which have enabled asteroseismology of these stars
Summary
White dwarf stars are the most common endpoint of stellar evolution and are the ultimate fate of all stars with masses less than about 8–10 Mo (Woosley and Heger, 2015). This impasse, the favorable experience with 2-site data, and a desire to perform asteroseismology of white dwarfs amongst the community led to the development of the WET (Nather, 1989; Nather et al, 1990) With this said, we can turn to the main point of this article, which is to show how minimizing the single-site daylight observing gaps can reduce the alias pattern and make asteroseismology possible. We refer the reader to Winget et al (1994) for the definitive data analysis (see especially their Figures 3 and 7); our aim here is to graphically illustrate that the WET achieved the goal of nearly eliminating alias peaks and making asteroseismology of white dwarf stars possible. Based on the results of Bognar et al (2020), the limiting magnitude of TESS to observe pulsating white dwarfs is ∼17). Corsico et al (2021) have recently analysed TESS results for GD 358
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