How Gaps in Time-Series Data Affect Asteroseismic Interpretation

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.

Pulsating hydrogen-deficient white dwarfs and pre-white dwarfs observed with TESS

“…The star exhibits five periods between ∼ 649 s and ∼ 746 s ( riods (assumed to be m = 0 modes) of WD J1527 available from TESS for our asteroseismological analysis. If these periods were associated with low radial-order modes, they would be useful to establish strong asteroseismological constraints on the internal structure of WD J1527 (see, for example, the cases of the ZZ Ceti stars G226−29, G117−B15A, and R 548; Fontaine et al 1992;Kepler et al 1995;Bradley 1998). However, these three periods correspond to intermediate or high radial orders, lowering their asteroseismic potential.…”

Asteroseismological analysis of the polluted ZZ Ceti star G 29 − 38 with TESS

“…While ground-based observations over the years have been extremely important in studying the nature of DAV stars (e.g., Landolt 1968;Nather et al 1990;Mukadam et al 2004;Winget & Kepler 2008;Fontaine & Brassard 2008;Bradley 2021), observations from space have revolutionized the area of ZZ Ceti pulsations (Córsico 2020(Córsico , 2022. In particular, the K2 extension (Howell et al 2014) of the Kepler mission (Borucki et al 2010) allowed the discovery of outbursts in ZZ Cetis close to the red edge of the instability strip (Bell et al 2015;Luan & Goldreich 2018), and also the discovery that incoherent pulsations (Hermes et al 2017) can give information about the depth of the outer convection zone (Montgomery et al 2020).…”