Asteroseismology of the DOV star PG 1159 - 035 with the Whole Earth Telescope

Winget, D. E.; Nather, R. E.; Clemens, J. C.; Provençal, J. L.; Kleinman, S. J.; Bradley, P. A.; Wood, M. A.; Claver, C. F.; Frueh, M.; Grauer, A. D.; Hine, Butler; Hansen, Carl J.; Fontaine, G.; Achilleos, N.; Wickramasinghe, D. T.; Marar, T. M. K.; Seetha, S.; Ashoka, B. N.; O’Donoghue, D.; Warner, Brian D.; Kurtz, D. W.; Buckley, D. A. H.; Brickhill, John; Vauclair, G.; Dolez, N.; Chevreton, M.; Barstow, M. A.; Solheim, J. E.; Kanaan, A.; Kepler, S. O.; Henry, Gregory W.; Kawaler, Steven D.

doi:10.1086/170434

Cited by 256 publications

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“…With this simplified assumption, theory 19 predicts the occurrence of a constant period spacing among high-order gravity modes of the same degree. Such a spacing has been found and interpreted previously in white dwarfs, which are stellar remnants at the end of the life of stars like the Sun [20][21][22] . They had hitherto not been detected in main-sequence stars.…”

supporting

confidence: 72%

Deviations from a uniform period spacing of gravity modes in a massive star

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Aerts

Baglin

et al. 2010

Nature

168

211

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The life of a star is dominantly determined by the physical processes in the stellar interior. Unfortunately, we still have a poor understanding of how the stellar gas mixes near the stellar core, preventing precise predictions of stellar evolution 1 . The unknown nature of the mixing processes as well as the extent of the central mixed region is particularly problematic for massive stars 2 . Oscillations in stars with masses a few times that of the Sun offer a unique opportunity to disentangle the nature of various mixing processes, through the distinct signature they leave on period spacings in the gravity mode spectrum 3 . Here we report the detection of numerous gravity modes in a young star with a mass of about seven solar masses. The mean period spacing allows us to estimate the extent of the convective core, and the clear periodic deviation from the mean constrains the location of the chemical transition zone to be at about 10 per cent of the radius and rules out a clearcut profile.The young massive star HD 50230 is poorly studied, but it is known to have spectral type B3V and a visual magnitude of 8.95. HD 50230 is in its central nuclear-burning phase, just like the Sun, transforming hydrogen into helium in its core (the so-called main sequence phase). This important evolutionary phase covers about 90% of the life of the star, and the detailed internal structure of the star during this phase determines its ultimate fate 1,2 . This star is at the limiting mass of ending either as core-collapse supernova or as a white dwarf, enriching the interstellar medium with helium and heavy metals in the former case and carbon in the latter. A highquality continuous photometric light curve with 32-s sampling and with a span of 137 days has been obtained for the star by the Convection Rotation and Planetary Transits (CoRoT 4 ) satellite. A linear downward trend was removed from the data, after outliers were excluded from the light curve. The duty cycle of the final set of measurements analysed here is 88.6% and the noise has an amplitude of 1 mmag (Fig. 1). The light curve reveals the presence of numerous oscillation modes.Stellar oscillations have been found to occur at different stages of stellar life, for a range of stellar masses 5 . The best known case is that of the solar oscillations, which are acoustic modes with periods near 5 min (refs 6-9). The seismic interpretation of the detected solar oscillations led to a drastic improvement in the knowledge of the internal structure of the Sun 10,11 . Meanwhile, similar acoustic modes have been detected in various types of distant stars [12][13][14] . Gravity modes, on the other hand, probe much deeper layers inside stars and in principle allow the study of the core properties of stars far better than acoustic modes. Although such modes have been detected in massive stars similar to HD 50230 15,16 , where they have typical periods of half a day to a few days, their seismic potential could not be exploited because the number of detected modes in one star was far too lo...

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supporting

confidence: 72%

Deviations from a uniform period spacing of gravity modes in a massive star

Degroote

Aerts

Baglin

et al. 2010

Nature

168

211

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“…Also, the splitting of these multiplets should be different for different values of . In one star, PG 1159, Winget et al (1991) show that these two effects are present: a sequence of triplet modes are split by equal amounts, and are nearly exactly 0.6 times the splitting seen in several quintuplets. The theory works quite well.…”

Section: Asteroseismologymentioning

confidence: 92%

White Dwarf Rotation: Observations and Theory

Kawaler¹

2004

Symp. - Int. Astron. Union

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Abstract. White dwarfs rotate. The angular momentum in single white dwarfs must originate early in the life of the star, but also must be modified (and perhaps severely modified) during the many stages of evolution between birth as a mainsequence star and final appearance as a white dwarf. Observational constraints on the rotation of single white dwarf stars come from traditional spectroscopy and from asteroseismology, with the latter providing hints of angular velocity with depth. Results of these observational determinations, that white dwarfs rotate with periods ranging from hours to days (or longer), tells us that the processes by which angular momentum is deposited and/or drained from the cores of AGB stars are complex. Still, one can place strong limits on these processes by considering relatively simple limiting cases for angular momentum evolution in prior stages, and on subsequent angular momentum evolution in the white dwarfs. These limiting-case constraints will be reviewed in the context of the available observations.

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“…More than a decade after the outstanding successes with PG 1159 and GD 358 (Winget et al 1991(Winget et al , 1994, the Whole Earth Telescope (WET; Nather et al 1990) continues to look for variable white dwarfs with rich pulsation spectra. Unfortunately we have learned that these stars are truly exceptional -either in the number and variety of their intrinsic variations, or in our ability (and luck) to detect so many modes.…”

Section: Introductionmentioning

confidence: 99%

The Consequences of Assuming m=0 for Global Model-Fitting

Metcalfe

2003

Open Astronomy

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Abstract.A recent re-analysis of Whole Earth Telescope observations of GD 358 obtained in 1990 suggest that asteroseismology of additional DBV white dwarfs can lead to independent constraints on the important, but poorly determined, 12 C(α, γ) 16 O nuclear reaction rate. Data exist for several other DBV white dwarfs, but relatively few modes are detected and there is often no multiplet structure to aid in the identification of the spherical harmonic indices l,m. I use a new grid of one million DBV models covering a broad range of masses, temperatures, and surface helium layer masses to investigate the consequences of assuming m=0 for global model-fitting. I find that when the spherical degree is known and the rotation period is of order 1 day, the model-fitting procedure applied to modes with unknown m values will still correctly identify the families of possible solutions, and has a high probability of identifying the same globally optimal solution found when the m-value is known.

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Asteroseismology of the DOV star PG 1159 - 035 with the Whole Earth Telescope

Cited by 256 publications

References 0 publications

Deviations from a uniform period spacing of gravity modes in a massive star

Deviations from a uniform period spacing of gravity modes in a massive star

White Dwarf Rotation: Observations and Theory

The Consequences of Assuming m=0 for Global Model-Fitting

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