Unlocking the Secrets of White Dwarf Stars

Horn, Van; Hugh, M

doi:10.1007/978-3-319-09369-7

Cited by 10 publications

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“…The behavior of carbon at millions to billions of atmospheres of pressure is integral to evolution models for many solar and extrasolar planets (Uranus, Neptune, 55 Cancri E) 1,2 and white dwarf stars. 3,4 In Uranus and Neptune, carbon exists in the form of methane (CH 4 ) ice at the surface but may be in its elemental form near the core where pressures and temperatures reach ∼8 Mbar and ∼8000 K, respectively. 5,6 Theoretical predictions suggest that the interiors of Uranus, Neptune, or Neptune-like exoplanets might contain diamond or even liquid oceans of carbon.…”

Section: Introductionmentioning

confidence: 99%

Hugoniot and release measurements in diamond shocked up to 26 Mbar

et al. 2017

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The equation of state (EOS) of carbon in its high-pressure solid and liquid phases is of interest to planetary astrophysics and inertial confinement fusion. Of particular interest are the high-pressure shock and release responses of diamond as these provide rigorous constraints on important paths through the EOS. This article presents experimental Hugoniot and release data for both singlecrystal diamond (SCD) and nanocrystalline diamond (NCD), which is comprised of nanometer-scale diamond grains and is ∼5% less dense than SCD. We find that NCD has a stiffer Hugoniot than SCD that can be attributed to porosity. A Grüneisen parameter of ∼1 was derived from the data, which suggests increased coordination in the high-pressure fluid carbon compared to ambient diamond.

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Section: Introductionmentioning

confidence: 99%

Hugoniot and release measurements in diamond shocked up to 26 Mbar

et al. 2017

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“…Curiously, this object was already identified as a variable star and had been given the variable star name ZZ Ceti. R584 then became the prototype of the new class of pulsating white dwarfs known as ZZ Cetis (Van Horn 2015). By 2007, around 126 ZZ Cetis had been discovered (Kepler 2007).…”

Section: Introductionmentioning

confidence: 99%

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

Romero

Hermes

Amaral

et al. 2022

Monthly Notices of the Royal Astronomical Society

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We report the discovery of 74 new pulsating DA white dwarf stars, or ZZ Cetis, from the data obtained by the Transiting Exoplanet Survey Satellite (TESS) mission, from Sectors 1 to 39, corresponding to the first 3 cycles. This includes objects from the Southern Hemisphere (Sectors 1–13 and 27–39) and the Northern Hemisphere (Sectors 14–26), observed with 120 s- and 20 s-cadence. Our sample likely includes 13 low-mass and one extremely low-mass white dwarf candidate, considering the mass determinations from fitting Gaia magnitudes and parallax. In addition, we present follow-up time series photometry from ground-based telescopes for 11 objects, which allowed us to detect a larger number of periods. For each object, we analysed the period spectra and performed an asteroseismological analysis, and we estimate the structure parameters of the sample, i.e. stellar mass, effective temperature and hydrogen envelope mass. We estimate a mean asteroseismological mass of 〈Msis〉= 0.635± 0.015 M⊙, excluding the candidate low or extremely-low mass objects. This value is in agreement with the mean mass using estimates from Gaia data, which is 〈Mphot〉= 0.631± 0.040 M⊙, and with the mean mass of previously known ZZ Cetis of 〈M*〉= 0.644 ± 0.034 M⊙. Our sample of 74 new bright ZZ Cetis increases the number of known ZZ Cetis by ∼20 per cent.

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“…The emergence of the quantum-mechanics theory towards the first quarter of the 20 th century paved the way to explain the existence of white dwarfs. An excellent historical account of the discovery of white dwarfs and the theoretical arguments that led to explain the existence of these compact objects in nature is provided by Van Horn (2015).…”

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confidence: 99%

White-dwarf asteroseismology with the Kepler space telescope

Córsico¹

2020

Preprint

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In the course of their evolution, white-dwarf stars go through at least one phase of variability in which the global pulsations they undergo allow astronomers to peer into their interiors, this way making possible to shed light on their deep inner structure and evolutionary stage by means of asteroseismology. The study of pulsating white dwarfs has witnessed substantial progress in the last decade, and this has been so largely thanks to the arrival of continuous observations of unprecedented quality from space, like those of the CoRoT, Kepler, and TESS missions. This, along with the advent of new detailed thoretical models and the development of improved asteroseismological techniques, has helped to unravel the internal chemical structure of many pulsating white dwarfs, and, at the same time, has opened new questions that challenge theoreticians. In particular, uninterrupted monitoring of white-dwarf stars for months has allowed discovering phenomena impossible to detect with ground-based observations, despite admirable previous efforts like the Whole Earth Telescope (WET). Here, we start by reviewing the essential properties of white-dwarf and pre-white dwarf stars and their pulsations, and then, we go through the different families of pulsating objects known to date. Finally, we review the most outstanding findings about pulsating white dwarfs and pre-white dwarfs made possible with the unprecedentedquality observations of the Kepler space telescope, although we envisage that future analyzes of space data from this mission that still await to be examined may reveal new secrets of these extremely interesting variable stars.

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Unlocking the Secrets of White Dwarf Stars

Cited by 10 publications

References 0 publications

Hugoniot and release measurements in diamond shocked up to 26 Mbar

Hugoniot and release measurements in diamond shocked up to 26 Mbar

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

White-dwarf asteroseismology with the Kepler space telescope

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