Pulsating white dwarfs

Romero, A. D.

doi:10.1051/epjconf/201715201011

Cited by 14 publications

(10 citation statements)

References 81 publications

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“…We used a gray atmosphere for the entire evolution. Considering white dwarf stars has rotation periods of ∼ 1 day (Kepler & Romero 2017), in most cases, the effects of rotation are negligible. Even thought there are a few known fast rotators, we do no consider rotation in our computations.…”

Section: Pre-white Dwarf Evolutionmentioning

confidence: 99%

New full evolutionary sequences of H- and He-atmosphere massive white dwarf stars using mesa

Lauffer

Romero

2018

Monthly Notices of the Royal Astronomical Society

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We explore the evolution of hydrogen-rich and hydrogen-deficient white dwarf stars with masses between 1.012 and 1.307 M , and initial metallicity of Z = 0.02. These sequences are the result of main sequence stars with masses between 8.8 and 11.8 M .The simulations were performed with MESA, starting at the zero-age main sequence, through thermally pulsing and mass-loss phases, ending at the white dwarfs cooling sequence. We present reliable chemical profiles for the whole mass range considered, covering the different expected central compositions, i.e. C/O, O/Ne and Ne/O/Mg, and its dependence with the stellar mass. In addition, we present detailed chemical profiles of hybrid C/O-O/Ne core white dwarfs, found in the mass range between 1.024 and 1.15 M . We present the initial-to-final mass relation, mass-radius relation, and cooling times considering the effects of atmosphere and core composition.

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Section: Pre-white Dwarf Evolutionmentioning

confidence: 99%

New full evolutionary sequences of H- and He-atmosphere massive white dwarf stars using mesa

Lauffer

Romero

2018

Monthly Notices of the Royal Astronomical Society

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“…In view of these considerations, and despite the numerous discoveries of pulsating WD stars in the last decade, both from the ground and from space, it is surprising that no warm DAV WD has been detected thus far. Ground-based observations, particularly carried out with the spectral observations of the Sloan Digital Sky Survey (SDSS; York et al 2000), have increased the number of known WDs by a factor of 15 (Kleinman et al 2013;Kepler et al 2016Kepler & Romero 2017;Gentile Fusillo et al 2019) and the number of pulsators by a factor of 4 (Mukadam et al 2004;Mullally et al 2005;Castanheira et al 2006;Voss et al 2007;Nitta et al 2009;Castanheira et al 2013). On the other hand, the Kepler satellite observations, both main mission (Borucki et al 2010) andK2 (two-wheel operation, Howell et al 2014), increased the number of known WD pulsators by a factor of 2 (Hermes et al 2017).…”

Section: Introductionmentioning

confidence: 99%

About the existence of warm H-rich pulsating white dwarfs

Althaus

Córsico

Uzundag

et al. 2019

A&A

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Context. The possible existence of warm (T eff ∼ 19 000 K) pulsating DA white dwarf (WD) stars, hotter than ZZ Ceti stars, was predicted in theoretical studies more than 30 yr ago. These studies reported the occurrence of g-mode pulsational instabilities due to the κ mechanism acting in the partial ionization zone of He below the H envelope in models of DA WDs with very thin H envelopes (M H /M ⋆ 10 −10 ). However, to date, no pulsating warm DA WD has been discovered, despite the varied theoretical and observational evidence suggesting that a fraction of WDs should be formed with a range of very low H content. Aims. We re-examine the pulsational predictions for such WDs on the basis of new full evolutionary sequences. We analyze all the warm DAs observed by TESS satellite up to Sector 9 in order to search for the possible pulsational signal. Methods. We compute WD evolutionary sequences of masses 0.58 and 0.80 M ⊙ with H content in the range −14.5 log(M H /M ⋆ ) −10, appropriate for the study of pulsational instability of warm DA WDs. Initial models were extracted from progenitors that were evolved through very late thermal pulses on the early cooling branch. We use LPCODE stellar code to which we have incorporated a new full-implicit treatment of time-dependent element diffusion for precisely modeling the H/He transition zone in evolving WD models with very low H content. The non-adiabatic pulsations of our warm DA WD models were computed in the effective temperature range of 30 000 − 10 000 K, focusing on ℓ = 1 g modes with periods in the range 50 − 1500 s. Results. We find that traces of H surviving the very late thermal pulse float to the surface, eventually forming growing, thin pure H envelopes and rather extended H/He transition zones. We find that such extended transition zones inhibit the excitation of g modes due to partial ionization of He below the H envelope. Only in the case that the H/He transition is assumed much more abrupt than predicted by diffusion, models do exhibit pulsational instability. In this case, instabilities are found only in WD models with H envelopes in the range of −14.5 log(M H /M ⋆ ) −10 and at effective temperatures higher than those typical of ZZ Ceti stars, in agreement with previous studies. None of the 36 warm DAs observed so far by TESS satellite are found to pulsate. Conclusions. Our study suggests that the non-detection of pulsating warm DAs, if WDs with very thin H envelopes do exist, could be attributed to the presence of a smooth and extended H/He transition zone. This could be considered as an indirect proof that element diffusion indeed operates in the interior of WDs.

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“…In this review, we will not focus on the details about the asteroseismological tools applied to pulsating WDs, which can be found in Fontaine and Brassard (2008); Winget and Kepler (2008); Althaus et al (2010b), Kepler and Romero (2017), and Giammichele et al (2017b). Instead, we will concentrate on the advancements made in the study of pulsating WDs in the last decade.…”

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Pulsating white dwarfs: new insights

Córsico

Althaus

Bertolami

et al. 2019

Astron Astrophys Rev

204

224

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Stars are extremely important astronomical objects that constitute the pillars on which the Universe is built, and as such, their study has gained increasing interest over the years. White dwarf stars are not the exception. Indeed, these stars constitute the final evolutionary stage for more than 95 per cent of all stars. The Galactic population of white dwarfs conveys a wealth of information about several fundamental issues and are of vital importance to study the structure, evolution and chemical enrichment of our Galaxy and its components -including the star formation history of the Milky Way. Several important studies have emphasized the advantage of using white dwarfs as reliable clocks to date a variety of stellar populations in the solar neighborhood and in the nearest stellar clusters, including the thin and thick disks, the Galactic spheroid and the system of globular and open clusters. In addition, white dwarfs are tracers of the evolution of planetary systems along several phases of stellar evolution. Not less relevant than these applications, the study of matter at high densities has benefited from our detailed knowledge about evolutionary and observational properties of white dwarfs. In this sense, white dwarfs are used as laboratories for astro-particle physics, being their interest focused on physics beyond the standard model, that is, neutrino physics, axion physics and also radiation from "extra dimensions", and even crystallization.The last decade has witnessed a great progress in the study of white dwarfs. In particular, a wealth of information of these stars from different surveys has

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Pulsating white dwarfs

Cited by 14 publications

References 81 publications

New full evolutionary sequences of H- and He-atmosphere massive white dwarf stars using mesa

New full evolutionary sequences of H- and He-atmosphere massive white dwarf stars using mesa

About the existence of warm H-rich pulsating white dwarfs

Pulsating white dwarfs: new insights

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