A measurement of secular evolution in the pre-white dwarf star

Winget, D. E.; Kepler, S. O.; Robinson, E. L.; Nather, R. E.; O’Donoghue, D.

doi:10.1086/163193

Cited by 91 publications

(55 citation statements)

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“…The strip includes both the stars without evidence of surrounding planetary nebulae (McGraw 1979, and the PNNs . Winget et al 1985;Kawaler 1986;Costa, Kepler & Winget 1999). The pulsation periods range from 400 to 3000 s---longer for the PNNs (Vauclair, Solheim & Østensen 2005).…”

Section: Dovsmentioning

confidence: 99%

Pulsating White Dwarf Stars and Precision Asteroseismology

Winget

Kepler

2008

Annu. Rev. Astron. Astrophys.

350

321

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■ AbstractGalactic history is written in the white dwarf stars. Their surface properties hint at interiors composed of matter under extreme conditions. In the forty years since their discovery, pulsating white dwarf stars have moved from side-show curiosities to center stage as important tools for unraveling the deep mysteries of the Universe. Innovative observational techniques and theoretical modeling tools have breathed life into precision asteroseismology. We are just learning to use this powerful tool, confronting theoretical models with observed frequencies and their time rate-of-change. With this tool, we calibrate white dwarf cosmochronology; we explore equations of state; we measure stellar masses, rotation rates, and nuclear reaction rates; we explore the physics of interior crystallization; we study the structure of the progenitors of Type Ia supernovae, and we test models of dark matter. The white dwarf pulsations are at once the heartbeat of galactic history and a window into unexplored and exotic physics. A TASTE OF HISTORYThe history of science contains blueprints for the future. We see common threads running through much of the stories of past progress and discovery. Looking back at the history of scientific achievement, we see this theme repeated many times: meaningful progress requires that theory and experiment advance together. They must coordinate like two legs of a child learning to walk. If one leg gets too far ahead, the child falls. To move forward again, the child is forced to gather both legs together to stand. Examples when one leg gets farther in front are numerous in all fields of science. An early astronomical example is the Greek idea that the Earth might orbit the Sun. Searching for and not finding parallax, they abandoned the idea---the observational techniques of the time were not adequate. More recently, the cosmic background radiation might have been discovered in the 1940s through the observations of interstellar lines, were it not for lack of a theoretical context. Our analogy works in another way: It doesn't matter too much which leg takes the first step as long as they stay close enough together. Kepler built his laws on Tycho's careful observations; Newton "stood on the shoulders of giants;" Einstein's general relativistic description of gravity required Eddington and a total solar eclipse to be taken seriously.The attentive reader will see many parallels throughout this review between the quantum theory of the atom and white dwarf stars. The structure of both is determined through the delicate balance of a strong central force against the uncertainty and exclusion principles. Not surprisingly, their stories are intertwined; the white dwarf stars have a long history as a cosmic laboratory for quantum physics and general relativity.We are not historians; the science we review is of a more humble nature than these lofty examples. We offer the history of the field---from the inevitably biased viewpoint of your guides---as an introduction and a starting point for a blueprint...

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Section: Dovsmentioning

confidence: 99%

Pulsating White Dwarf Stars and Precision Asteroseismology

Winget

Kepler

2008

Annu. Rev. Astron. Astrophys.

350

321

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“…Our preferred methodology involves bootstrapping to determine a period precise enough to bridge multiple runs without losing a cycle count (e.g., Winget et al 1985). Unfortunately, weather and scheduling frustrations resulted in multiple-month gaps between successful observing sequences that are too large to bridge with this method.…”

Section: Time-series Photometry and Analysismentioning

confidence: 99%

Photometric Variability in a Warm, Strongly Magnetic Dq White Dwarf, SDSS J103655.39+652252.2

Williams

Winget

Montgomery

et al. 2013

ApJ

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We present the discovery of photometric variability in the DQ white dwarf SDSS J103655.39+652252.2 (SDSS J1036+6522). Time-series photometry reveals a coherent monoperiodic modulation at a period of 1115.64751(67) s with an amplitude 0.442% ± 0.024%; no other periodic modulations are observed with amplitudes 0.13%. The period, amplitude, and phase of this modulation are constant within errors over 16 months. The spectrum of SDSS J1036+6522 shows magnetic splitting of carbon lines, and we use Paschen-Back formalism to develop a grid of model atmospheres for mixed carbon and helium atmospheres. Our models, while reliant on several simplistic assumptions, nevertheless match the major spectral and photometric properties of the star with a self-consistent set of parameters: T eff ≈ 15,500 K, log g ≈ 9, log(C/He) = −1.0, and a mean magnetic field strength of 3.0 ± 0.2 MG. The temperature and abundances strongly suggest that SDSS J1036+6522 is a transition object between the hot, carbon-dominated DQs and the cool, heliumdominated DQs. The variability of SDSS J1036+6522 has characteristics similar to those of the variable hot carbon-atmosphere white dwarfs (DQVs), however, its temperature is significantly cooler. The pulse profile of SDSS J1036+6522 is nearly sinusoidal, in contrast with the significantly asymmetric pulse shapes of the known magnetic DQVs. If the variability in SDSS J1036+6522 is due to the same mechanism as other DQVs, then the pulse shape is not a definitive diagnostic on the absence of a strong magnetic field in DQVs. It remains unclear whether the root cause of the variability in SDSS J1036+6522 and the other hot DQVs is the same.

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“…the observed non-radial g-mode pulsations (e.g. Kepler 1984) are global pulsations, with each pulsation mode constraining the stellar structure in a different way, we can use the pulsations to untangle the structure of the whole star (Winget et al 1991Kepler et al 2003;Metcalfe 2003) and even their rates of evolution (Winget et al 1985;Costa et al 1999Costa et al , 2003Kepler et al 2000Kepler et al , 2005Mukadam et al 2003). These measured evolutionary rates have been used to calculate the age of the coolest known white dwarf stars, allowing an estimative of the age of the galactic disk (Winget et al 1987) and of a globular cluster (Hansen et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Discovery of fourteen new ZZ Cetis with SOAR

Castanheira

Saraiva

Nitta³

et al. 2005

A&A

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We report the discovery of fourteen new ZZ Cetis with the 4.1 m Southern Astrophysical Research telescope, at Cerro Pachon, in Chile. The candidates were selected from the SDSS (Sloan Digital Sky Survey) DA white dwarf stars with T eff obtained from the optical spectra fit, inside the ZZ Ceti instability strip. Considering these stars are multi-periodic pulsators and the pulsations propagate to the nucleus of the star, they carry information on the structure of the star and evolution of the progenitors. The ZZ Cetis discovered till 2003 are mainly within 100 pc from the Sun, and probe only the solar vicinity. The recently discovered ones, and those reported here, may sample a distinct population as they were selected mainly perpendicular to the galactic disk and cover a distance up to ≈400 pc.

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A measurement of secular evolution in the pre-white dwarf star

Cited by 91 publications

References 0 publications

Pulsating White Dwarf Stars and Precision Asteroseismology

Pulsating White Dwarf Stars and Precision Asteroseismology

Photometric Variability in a Warm, Strongly Magnetic Dq White Dwarf, SDSS J103655.39+652252.2

Discovery of fourteen new ZZ Cetis with SOAR

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