The discovery of nonradial instability strips for hot, evolved stars

Starrfield, S.; Cox, A. N.; Hodson, S. W.; Pesnell, W. D.

doi:10.1086/184023

Cited by 57 publications

(45 citation statements)

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“…This is at least an order of magnitude more accurate than the determinations from spectral fitting. As convection is negligible in these stars, the κ γ − mechanisms at the C and O partial ionization zones are the main drivers, as originally proposed by Starrfield et al (1983) and confirmed by Bradley (1996), and more accurately confirmed with the evolutionary models of Quirion, Fontaine & Brassard (2004, , and Córsico, . There are pulsators and nonpulsators in the same region of the Hertzsprung-Russell diagram, but there are significant abundance differences.…”

Section: Dovssupporting

confidence: 75%

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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: Dovssupporting

confidence: 75%

“…in DA white dwarf models, followed nearly simultaneously by others (Winget, Van Horn & Hansen 1981;Starrfield et al 1982;Winget et al 1982a). Theorists were finally able to find in their models the association of the excitation by the zone of partial H ionization discovered by McGraw.…”

Section: Sorting Out the Pulsating White Dwarf Starsmentioning

confidence: 80%

Pulsating White Dwarf Stars and Precision Asteroseismology

Winget

Kepler

2008

Annu. Rev. Astron. Astrophys.

350

321

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“…The earliest theoretical investigations of the boundaries of the instability strip for ZZ Ceti stars were made, for lack of a better approach, within the frozen convection (FC) approximation (see, e.g., Dolez & Vauclair 1981;Dziembowski & Koester 1981;Winget et al 1982;Winget 1982;Starrfield et al 1982). It was in the meantime realized (see, e.g., Brickhill 1983, and references therein) that, at least at the blue edge, the turnover timescale in the convection zone of a ZZ Ceti star is, in fact, much smaller than the pulsation periods of interest.…”

Section: Introductionmentioning

confidence: 99%

The instability strip of ZZ Ceti white dwarfs

Grootel

Dupret

Fontaine

et al. 2012

A&A

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Aims. The determination of the location of the theoretical ZZ Ceti instability strip in the log g − T eff diagram has remained a challenge over the years due to the lack of a suitable treatment for convection in these stars. For the first time, a full nonadiabatic approach including time-dependent convection is applied to ZZ Ceti pulsators, and we provide the appropriate details related to the inner workings of the driving mechanism. Methods. We used the nonadiabatic pulsation code MAD with a representative evolutionary sequence of a 0.6 M DA white dwarf. This sequence is made of state-of-the-art models that include a detailed modeling of the feedback of convection on the atmospheric structure. The assumed convective efficiency in these models is the so-called ML2/α = 1.0 version. We also carried out, for comparison purposes, nonadiabatic computations within the frozen convection approximation, as well as calculations based on models with standard grey atmospheres. Results. We find that pulsational driving in ZZ Ceti stars is concentrated at the base of the superficial H convection zone, but at depths, near the blue edge of the instability strip, somewhat larger than those obtained with the frozen convection approach. Despite the fact that this approach is formally invalid in such stars, particularly near the blue edge of the instability strip, the predicted boundaries are not dramatically different in both cases. The revised blue edge for a 0.6 M model is found to be around T eff = 11 970 K, some 240 K hotter than the value predicted within the frozen convection approximation, in rather good agreement with the empirical value. On the other hand, our predicted red edge temperature for the same stellar mass is only about 5600 K (80 K hotter than with the frozen convection approach), much lower than the observed value. Conclusions. We correctly understand the development of pulsational instabilities of a white dwarf as it cools at the blue edge of the ZZ Ceti instability strip. Our current implementation of time-dependent convection however still lacks important ingredients to fully account for the observed red edge of the strip. We will explore a number of possibilities in the future papers of this series.

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“…The driving mechanism has been discussed in the past with considerable controversy. The basic ingredient, the κ-mechanism associated with the partial ionization zone of K-shell electrons of C and O in stellar model envelope just beneath the photosphere, has been identified in the pioneering work by Starrfield et al (1983). However, these models required a very He-deficient composition, in contrast to the observed surface chemistry.…”

Section: Introductionmentioning

confidence: 99%

Detection of non-radial g-mode pulsations in the newly discovered PG 1159 star HE 1429-1209

Nagel¹,

Werner²

2004

A&A

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Abstract. We performed time-series photometry of the PG 1159-type star HE 1429−1209, which was recently discovered in the ESO SPY survey. We show that the star is a low-amplitude (≈0.05 mag) non-radial g-mode pulsator with a period of 919 s. HE 1429−1209 is among the hottest known post-AGB stars (T eff = 160 000 K) and, together with the known pulsator RX J2117.1+3412, it defines empirically the blue edge of the GW Vir instability strip in the HRD at high luminosities.

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The discovery of nonradial instability strips for hot, evolved stars

Cited by 57 publications

References 0 publications

Pulsating White Dwarf Stars and Precision Asteroseismology

Pulsating White Dwarf Stars and Precision Asteroseismology

The instability strip of ZZ Ceti white dwarfs

Detection of non-radial g-mode pulsations in the newly discovered PG 1159 star HE 1429-1209

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