Discovery of 74 new bright ZZ Ceti stars in the first three years of <i>TESS</i>

Romero, A. D.; Hermes, J. J.; Amaral, Larissa Antunes; Uzundag, Murat; Bognár, Zsófia; Bell, Keaton J.; VanWyngarden, Madison; Baran, A.; Pelisoli, Ingrid; Oliveira, Gabriela da Rosa; Koester, D.; Klippel, Theylor Schumacher; Bradley, P. A.; Vučković, M.; Heintz, Tyler M.; Reding, Joshua S.; Kaiser, Bastian; Charpinet, S.

doi:10.1093/mnras/stac093

Cited by 21 publications

(30 citation statements)

References 74 publications

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“…Uninterrupted observations from current and future space missions such as TESS (Ricker et al 2015), Cheops (Moya et al 2018), and PLATO (Piotto 2018), together with the Gaia (Gaia Collaboration 2016) data, are expected to dramatically increase the number of ZZ Ceti stars (see Romero et al 2022), providing unprecedented high-quality observations (Córsico 2020(Córsico , 2022. The interpretation of these data demands the development of a new generation of fully evolutionary ZZ Ceti models.…”

Section: Introductionmentioning

confidence: 99%

New DA white dwarf models for asteroseismology of ZZ Ceti stars

Althaus

Córsico

2022

A&A

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Context. Asteroseismology is a powerful tool used to infer the evolutionary status and chemical stratification of white dwarf stars and to gain insights into the physical processes that lead to their formation. This is particularly true for the variable hydrogen-rich atmosphere (DA) white dwarfs, known as DAV or ZZ Ceti stars. They constitute the most numerous class of pulsating white dwarfs. Aims. We present a new grid of white dwarf models that take into account advances made over the last decade in modeling and input physics of both the progenitor and the white dwarf stars. As a result, it is possible to avoid several shortcomings present in the set of white dwarf models employed in the asteroseismological analyses of ZZ Ceti stars that we carried out in our previous works. Methods. We generate white dwarf stellar models appropriate for ZZ Ceti stars with masses from ∼0.52 to ∼0.83 M⊙, resulting from the whole evolution of initially 1.5–4.0 M⊙ mass star models. These new models are derived from a self-consistent way with the changes in the internal chemical distribution that result from the mixing of all the core chemical components induced by mean molecular-weight inversions, from 22Ne diffusion, Coulomb sedimentation, and from residual nuclear burning. In addition, the expected nuclear-burning history and mixing events along the progenitor evolution are accounted for, in particular the occurrence of third dredge-up, which determines the properties of the core and envelope of post-AGB and white dwarf stars, as well as the white dwarf initial-final mass relation. The range of hydrogen envelopes of our new ZZ Ceti models extends from the maximum residual hydrogen content predicted by the progenitor history, log(MH/M⊙)∼ − 4 to −5, to log(MH/M⊙) = − 13.5, thus allowing for the first stellar models that would enable the search for seismological solutions for ZZ Ceti stars with extremely thin hydrogen envelopes – if, indeed, they do exist in nature. We computed the adiabatic gravity(g)-mode pulsation periods of these models. Calculations of our new evolutionary and pulsational ZZ Ceti models were performed with the LPCODE stellar evolution code and the LP-PUL stellar pulsation code. Results. Our new hydrogen-burning post-AGB models predict chemical structures for ZZ Ceti stars that are substantially different from those we used in our previous works, particularly in connection with the chemical profiles of oxygen and carbon near the stellar centre. We also discuss the implications of these new models for the pulsational spectrum of ZZ Ceti stars. Specifically, we find that the pulsation periods of g modes and the mode-trapping properties of the new models differ significantly from those characterizing the ZZ Ceti models of our previous works, particularly for long periods. Conclusions. The improvements in the modeling of ZZ Ceti stars we present here lead to substantial differences in the predicted pulsational properties of ZZ Ceti stars, which are expected to impact the asteroseismological inferences of these stars. This is extremely relevant in view of the abundant amount of photometric data from current and future space missions, resulting in discoveries of numerous ZZ Ceti stars.

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Section: Introductionmentioning

confidence: 99%

New DA white dwarf models for asteroseismology of ZZ Ceti stars

Althaus

Córsico

2022

A&A

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“…ZZ Cetis are pulsating WDs, possessing hydrogen atmospheres and pulsation periods ranging from tens of seconds to tens of minutes (Fontaine & Brassard 2008;Winget & Kepler 2008;Romero et al 2022). The presence of pulsations enable asteroseismological analyses to be performed, providing insight into the internal structure of the WD which is otherwise concealed by their highly stratified nature.…”

Section: Zz Ceti Wdsmentioning

confidence: 99%

Photometric follow-up of 43 new eclipsing white dwarf plus main-sequence binaries from the ZTF survey

Brown¹,

Parsons²,

Roestel³

et al. 2023

Preprint

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Wide-field time-domain photometric sky surveys are now finding hundreds of eclipsing white dwarf plus M dwarf binaries, a population encompassing a wealth of information and potential insight into white dwarf and close binary astrophysics. Precise follow-up observations are essential in order to fully constrain these systems and capitalise on the power of this sample. We present the first results from our program of high-speed, multi-band photometric follow-up. We develop a method to measure temperatures, (model-dependent) masses, and radii for both components from the eclipse photometry alone and characterize 34 white dwarf binaries, finding general agreement with independent estimates using an alternative approach while achieving around a factor of two increase in parameter precision. In addition to these parameter estimates, we discover a number of interesting systems -finding four with sub-stellar secondaries, doubling the number of eclipsing examples, and at least six where we find the white dwarf to be strongly magnetic, making these the first eclipsing examples of such systems and key to investigating the mechanism of magnetic field generation in white dwarfs. We also discover the first two pulsating white dwarfs in detached and eclipsing post-common-envelope binaries -one with a low-mass, likely helium core, and one with a relatively high mass, towards the upper end of the known sample of ZZ Cetis. Our results demonstrate the power of eclipse photometry, not only as a method of characterising the population, but as a way of discovering important systems that would have otherwise been missed by spectroscopic follow-up.

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“…To date, we have obtained pulsation spectra for 500 hydrogen-atmosphere white dwarfs (DAVs) and nearly 70 helium-atmosphere white dwarfs (Romero et al 2022;Vanderbosch et al 2022). Only a fraction of these have been the subject of asteroseismic fitting because we have not developed pipeline fitting for these objects yet.…”

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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Discovery of 74 new bright ZZ Ceti stars in the first three years of TESS

Cited by 21 publications

References 74 publications

New DA white dwarf models for asteroseismology of ZZ Ceti stars

New DA white dwarf models for asteroseismology of ZZ Ceti stars

Photometric follow-up of 43 new eclipsing white dwarf plus main-sequence binaries from the ZTF survey

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

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