Nonlinear effects in time-resolved spectra of DAVs

Ising, J.; Koester, D.

doi:10.1051/0004-6361:20010529

Cited by 26 publications

(45 citation statements)

References 20 publications

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“…Thus, the nearly sinusoidal shape of our lightcurves (Fig. 8) is a mystery, except for the theoretical models of Ising & Koester (2001), which predict sinusoidal shapes for large amplitude modes even with the nonlinear response of the envelope. After the P = 423 s mode reached its highest amplitude in run an-0034, the k = 9 P = 464 s mode started to grow and the 423 s became smaller, but there was still very little sign of the usually dominant k = 17 P = 770 s mode.…”

Section: Changes In the Dominant Mode In 1996mentioning

confidence: 82%

The everchanging pulsating white dwarf GD358

Kepler¹,

Nather

Winget

et al. 2003

A&A

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Abstract. We report 323 hours of nearly uninterrupted time series photometric observations of the DBV star GD 358 acquired with the Whole Earth Telescope (WET) during May 23rd to June 8th, 2000. We acquired more than 232 000 independent measurements. We also report on 48 hours of time-series photometric observations in Aug 1996. We detected the non-radial g-modes consistent with degree = 1 and radial order 8 to 20 and their linear combinations up to 6th order. We also detect, for the first time, a high amplitude = 2 mode, with a period of 796 s. In the 2000 WET data, the largest amplitude modes are similar to those detected with the WET observations of 1990 and 1994, but the highest combination order previously detected was 4th order. At one point during the 1996 observations, most of the pulsation energy was transferred into the radial order k = 8 mode, which displayed a sinusoidal pulse shape in spite of the large amplitude. The multiplet structure of the individual modes changes from year to year, and during the 2000 observations only the k = 9 mode displays clear normal triplet structure. Even though the pulsation amplitudes change on timescales of days and years, the eigenfrequencies remain essentially the same, showing the stellar structure is not changing on any dynamical timescale.

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Section: Changes In the Dominant Mode In 1996mentioning

confidence: 82%

The everchanging pulsating white dwarf GD358

Kepler¹,

Nather

Winget

et al. 2003

A&A

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“…Even though Ising & Koester (2001) and Weidner & Koester (2003) show that the effect of the convective zone introduces nonlinearities, the amplitude and inclination angle dependence in A(λ) are negligible for small (or large) amplitudes.…”

Section: Amplitude Variation With Wavelengthmentioning

confidence: 99%

HST observations of the pulsating white dwarf GD 358

Castanheira¹,

Nitta²,

Winget

et al. 2005

A&A

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Abstract. We used time-resolved ultraviolet spectroscopy obtained with the FOS and STIS spectrographs of the Hubble Space Telescope (HST), together with archival IUE observations to measure the effective temperature (T eff ), surface gravity (log g) and distance (d) of the pulsating DB white dwarf GD 358 with unprecedented accuracy, and to show that the temperature did not change during the 1996 sforzando, when the star changed basically to a single mode pulsator. We also measured for the first time for a DBV the spherical harmonic degree ( ) for two modes, with k = 8 and k = 9, which was only possible because the stellar light curve was dominated by a single mode in 1996. The independent spectra provide the following values: T eff = 24 100 ± 400 K, log g = 7.91 ± 0.26 and d = 42.7 ± 2.5 pc. The ultraviolet spectroscopic distance is in better agreement with the seismological value, than the one derived by parallax.

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“…The first, by Brickhill [1], includes the interaction and feedback between the pulsations and the convection zone of the star.The second, by Brassard et al [2], considers the nonlinearities to be due to the nonlinear relation between temperature change and the visible flux emitted. The model by Brickhill has subsequently been expounded upon by others [3,4,5,6,7]. In its current formulation, the photospheric flux leaving the top of the convection zone is related to the flux entering it at the base of the convection zone, by…”

Section: Astrophysical Contextmentioning

confidence: 99%