Seismological Studies of Pulsating DA White Dwarfs Observed with the Kepler Space Telescope and K2 Campaigns 1–8

Hall, Weston; Castanheira, B. G.; Kim, Agnès

doi:10.3847/1538-4357/acc52c

Cited by 2 publications

(2 citation statements)

References 39 publications

(62 reference statements)

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“…From stellar evolution calculations, we know that this is not physical (e.g., Córsico et al 2019). Hall et al (2023) performed the asteroseismic fitting of 29 DAVs observed with the Kepler and K2 missions. More physical, but still fixed, oxygen profiles were considered.…”

Section: Astrophysical Contextmentioning

confidence: 99%

A Systematic Study of the Connection Between White Dwarf Period Spectra and Model Structure

Bischoff-Kim

2023

ApJ

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To date, pulsational variability has been measured for nearly 70 pulsating helium-atmosphere white dwarfs (DBVs) and 500 pulsating hydrogen-atmosphere white dwarfs (DAVs), with only a fraction of these having been the subject of asteroseismic analysis. One way to approach white dwarf asteroseismology is forward modeling, where one assumes an interior structure and calculates the model’s periods. Many such models are calculated, in the search for the one that best matches the observed period spectrum. It is not computationally manageable, nor necessary, to vary every possible parameter for every object. We engage in a systematic study, based on a sample of 14 hydrogen-atmosphere white dwarfs, chosen to be representative of the types of pulsation spectra we encounter in white dwarf asteroseismology. These white dwarfs are modeled with carbon and oxygen cores. Our goal is to draw a connection between the period spectra and what parameters to which they are most sensitive. We find that the presence of longer-period modes generally muddies the mass and effective temperature determinations, unless continuous sequences of ℓ = 1 and ℓ = 2 modes are present. All period spectra are sensitive to the structure in the helium and hydrogen envelopes and most to at least some features of the oxygen abundance profile. Such sensitivity can be achieved either by the presence of specific low-radial-overtone modes, or by the presence of longer-period modes. Convective efficiency only matters when fitting periods greater than 800 s. The results of this study can be used to inform parameter selection and pave the way to pipeline asteroseismic fitting of white dwarfs.

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Section: Astrophysical Contextmentioning

confidence: 99%

A Systematic Study of the Connection Between White Dwarf Period Spectra and Model Structure

Bischoff-Kim

2023

ApJ

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“…The two studies used different carbon-oxygen core structures, so it is not surprising that they found different solutions when it came to the helium and hydrogen layer masses. A more recent study using WDEC but with (still fixed) carbon-oxygen core profiles chosen to mimic those resulting from fully evolutionary models still found a majority of models with thinner hydrogen layers (23 out of 29; Hall et al 2023).…”

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confidence: 99%

Constraints from Parallaxes and Average Period Spacings in the Asteroseismic Study of Eight Hydrogen-atmosphere Pulsating White Dwarfs

Bischoff-Kim,

Bell

2024

ApJ

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With space missions such as Kepler, TESS, and Gaia, we have a wealth of data on pulsating white dwarfs that can be leveraged in white dwarf asteroseismology. We address the question of the proportion of white dwarfs with thin hydrogen layers versus those with thick hydrogen layers. We also provide a mass–radius relation for carbon–oxygen-core, hydrogen-atmosphere white dwarfs. Such a relationship can be used in conjunction with magnitudes and distance measurements to constrain the mass and effective temperature of the white dwarfs. We select nine hydrogen-atmosphere pulsating white dwarfs for their rich pulsation spectra. From such pulsation spectra, we can derive the asymptotic period spacing, which in turn allows us to determine the thickness of the hydrogen and helium envelope of the models, without having to perform period-by-period fitting. We find that the majority of the white dwarfs have thicker hydrogen layers and we determine an upper limit of M r = 1–10−2.2 for the location of the base of the helium layer, in accordance with stellar evolution models. We confirm a finding from earlier studies that used a mass–radius relation and Gaia data to determine the effective temperatures of white dwarfs. The Gaia data systematically point to white dwarfs of lower effective temperature than indicated by the spectroscopy. Our results also support the hypothesis that white dwarfs with thicker hydrogen layers are more common than those with thinner layers.

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Seismological Studies of Pulsating DA White Dwarfs Observed with the Kepler Space Telescope and K2 Campaigns 1–8

Cited by 2 publications

References 39 publications

A Systematic Study of the Connection Between White Dwarf Period Spectra and Model Structure

A Systematic Study of the Connection Between White Dwarf Period Spectra and Model Structure

Constraints from Parallaxes and Average Period Spacings in the Asteroseismic Study of Eight Hydrogen-atmosphere Pulsating White Dwarfs

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