Seismological studies of ZZ Ceti stars - I. The model grid and the application to individual stars

Castanheira, B. G.; Kepler, S. O.

doi:10.1111/j.1365-2966.2008.12851.x

Cited by 62 publications

(97 citation statements)

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“…Asteroseismological inferences on individual pulsating white dwarfs provide in some cases constraints to the thickness of the H and He envelopes and the core composition of white dwarfs ). For instance, asteroseismological studies of DAVs carried out by Castanheira & Kepler (2008 indicate that the mass of the H envelope is in the range 10 −4 ∼ > M H /M * ∼ > 10 −10 , with a mean value of M H /M * = 5 × 10 −7 , thus suggesting that an important fraction of DAs characterized by envelopes substantially thinner than those predicted by standard evolution could exist. We emphasize that the initial chemical stratification of white dwarfs is not known with sufficient detail from the stellar evolution theory or from observations.…”

Section: Chemical Abundance Distributionmentioning

confidence: 99%

“…However, these results do not include the possible effects of realistic carbon-oxygen profiles on the fits. Almost simultaneously to the study of Castanheira & Kepler (2008 A summary of the asteroseismological inferences on individual ZZ Ceti stars performed so far is presented in Table 7 of Fontaine & Brassard (2008). As evident from what we said in the preceding paragraphs, there is no asteroseismological study of DAVs to date based on fully evolutionary models (generated from the ZAMS) that considers physically sound treatments to model the chemical interfaces at the core and the envelope of white dwarfs.…”

Section: Da White Dwarf Models and Asteroseismological Studies Of Davsmentioning

confidence: 99%

“…Recently, Castanheira & Kepler (2008) have carried out an extensive asteroseismological study of DAVs employing DA white dwarf models similar to those of Bradley (1996), but with a simplified treatment of the core chemical structure. Specificallym, they fixed the central abundances to 50 % of O and 50 % of C. The He/H chemical interfaces adopted for these models are a parametrization of chemical profiles resulting from time-dependent element diffusion (Althaus et al 2003).…”

Section: Da White Dwarf Models and Asteroseismological Studies Of Davsmentioning

confidence: 99%

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Evolutionary and pulsational properties of white dwarf stars

Althaus

Córsico

Isern

et al. 2010

Astron Astrophys Rev

368

372

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White dwarf stars are the final evolutionary stage of the vast majority of stars, including our Sun. Since the coolest white dwarfs are very old objects, the present population of white dwarfs contains a wealth of information on the evolution of stars from birth to death, and on the star formation rate throughout the history of our Galaxy. Thus, the study of white dwarfs has potential applications to different fields of astrophysics. In particular, white dwarfs can be used as independent reliable cosmic clocks, and can also provide valuable information about the fundamental parameters of a wide variety of stellar populations, like our Galaxy and open and globular clusters. In addition, the high densities and temperatures characterizing white dwarfs allow to use these stars as cosmic laboratories for studying physical processes under extreme conditions that cannot be achieved in terrestrial laboratories. Last but not least, since many white dwarf stars undergo pulsational instabilities, the study of their properties constitutes a powerful tool for applications beyond stellar astrophysics. In particular, white dwarfs can be used to constrain fundamental properties of elementary particles such as axions and neutrinos, and to study problems related to the variation of fundamental constants.These potential applications of white dwarfs have led to a renewed interest in the calculation of very detailed evolutionary and pulsational models for these stars. In this work, we review the essentials of the physics of white dwarf stars. We enumerate the reasons that make these stars excellent chronometers and we describe why white dwarfs provide tools for a wide variety of applications. Special emphasis is placed on the physical processes that lead to the formation of white dwarfs as well as on the different energy sources and processes responsible for chemical abundance changes that occur along their evolution. Moreover, in the course of their lives, white dwarfs cross different pulsational instability strips. The existence of these instability strips provides astronomers with an unique opportunity to peer into their internal structure that would otherwise remain hidden from observers. We will show that this allows to measure with unprecedented precision the stellar masses and to infer their envelope thicknesses, to probe the core chemical stratification, and to detect rotation rates and magnetic fields. Consequently, in this work, we also review the pulsational properties of white dwarfs and the most recent applications of white dwarf asteroseismology.

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Section: Chemical Abundance Distributionmentioning

confidence: 99%

Section: Da White Dwarf Models and Asteroseismological Studies Of Davsmentioning

confidence: 99%

Section: Da White Dwarf Models and Asteroseismological Studies Of Davsmentioning

confidence: 99%

See 1 more Smart Citation

Evolutionary and pulsational properties of white dwarf stars

Althaus

Córsico

Isern

et al. 2010

Astron Astrophys Rev

368

372

View full text Add to dashboard Cite

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“…Castanheira & Kepler 2008 and references therein), we expect that most of the detected frequencies are = 1. There is a recurring ≈9 μHz spacing in our datasets, and the most robust finding is the δ f = 9.6 μHz doublet in the WET2000 data.…”

Section: Stellar Rotationmentioning

confidence: 99%

Revealing the pulsational properties of the V777 Herculis star KUV 05134+2605 by its long-term monitoring

Bognár

Paparó

Córsico

et al. 2014

A&A

Self Cite

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Context. KUV 05134+2605 is one of the 21 pulsating DB white dwarfs (V777 Her or DBV variables) known so far. The detailed investigation of the short-period and low-amplitude pulsations of these relatively faint targets requires considerable observational efforts from the ground, long-term single-site or multi-site observations. The observed amplitudes of excited modes undergo short-term variations in many cases, which makes determining pulsation modes difficult. Aims. We aim to determine the pulsation frequencies of KUV 05134+2605, find regularities between the frequency and period components, and perform an asteroseismic investigation for the first time. Methods. We re-analysed the published data and collected new measurements. We compared the frequency content of the different datasets from the different epochs and performed various tests to check the reliability of the frequency determinations. The mean period spacings were investigated with linear fits to the observed periods, Kolmogorov-Smirnov and inverse variance significance tests, and with a Fourier analysis of different period sets, including a Monte Carlo test that simulated the effect of alias ambiguities. We employed fully evolutionary DB white dwarf models for the asteroseismic investigations. Results. We identified 22 frequencies between 1280 and 2530 μHz. These form 12 groups, which suggests at least 12 possible frequencies for the asteroseismic investigations. Thanks to the extended observations, KUV 05134+2605 joined the group of rich white dwarf pulsators. We identified one triplet and at least one doublet with a ≈9 μHz frequency separation, from which we derived a stellar rotation period of 0.6 d. We determined the mean period spacings of ≈31 s and 18 s for the modes we propose as dipole and quadrupole. We found an excellent agreement between the stellar mass derived from the = 1 period spacing and the period-to-period fits, all providing M * = 0.84−0.85 M solutions. Our study suggests that KUV 05134+2605 is the most massive amongst the known V777 Her stars.

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“…For compact pulsators, the Sloan Digital Sky Survey has been the tool to find and characterize new white dwarf and subdwarf stars, and led to the discovery of more than 200 new pulsators, mainly DAVs, also called ZZ Cetis (Mukadam et al 2004;Mullally et al 2005;Kepler et al 2005a;Castanheira et al 2006Castanheira et al , 2007, and their modelling (Castanheira & Kepler 2008, 2009Romero et al 2012Romero et al , 2013, but also DBVs Nitta et al (2009) and a few DOVs, also called variable PG 1159 or GW Vir stars (Quirion 2009a;Quirion, Fontaine & Brassard 2009b;Woudt, Warner,& Zietsman 2012;Kepler et al 2014). Two new classes of white dwarf pulsators were found, the DQVs (Montgomery et al 2008;Fontaine et al 2009;Williams et al 2013) and the ELMVs Hermes et al (2013a,b); Van Grootel et al (2012, 2013a; Córsico & Althaus (2014).…”

Section: Compact Oscillatorsmentioning

confidence: 99%