Observations of the Pulsating White Dwarf G 185–32

Castanheira, B. G.; Kepler, S. O.; Moskalik, P.; Zoła, S.; Pajdosz, G.; Krzesiński, Jurek; O’Donoghue, D.; Katz, Max; Buckley, D.; Vauclair, G.; Dolez, N.; Chevreton, M.; Barstow, M. A.; Kanaan, A.; Giovannini, O.; Provençal, J. L.; Kawaler, S. D.; Clemens, J. C.; Nather, R. E.; Winget, D. E.; Watson, T. K.; Yanagida, K.; Dixson, J. S.; Hansen, Carl J.; Bradley, P. A.; Wood, M. A.; Sullivan, D. J.; Kleinman, S. J.; Meistas, E.; Solheim, J. E.; Bruvold, A.; Leibowitz, E. M.; Mazeh, T.; Koester, D.; Montgomery, M. H.

doi:10.1051/0004-6361:20031567

Cited by 21 publications

(29 citation statements)

References 32 publications

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“…Figures 3 and 4 show the light curve and its Fourier transform (FT). The six largest periodicities in this data, the ones we concern ourselves with here, have all previously been observed on this star, most recently during a 76 hr run with WET (Castanheira et al 2004). Several other modes are present in Castanheira et al (2004), including possible frequency splittings of our F2 and F3.…”

Section: Ligg Ht and Velocity Curvv Essupporting

confidence: 52%

“…Since its discovery as a pulsator (McGraw et al 1981), it has been noted as having a curious pulsation spectrum. Atypical of small-amplitude pulsators, PY Vul displays a wide range of periods, including prominent modes near 370, 300, 215, 142, 72, and 71 s (McGraw et al 1981;Kepler et al 2000;Castanheira et al 2004). Given the star's shorter periods, low amplitudes, relatively stable modes, and temperature, this star is grouped with the pulsators near the blue edge of the instability strip.…”

Section: About Py Vulmentioning

confidence: 99%

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The Peculiar Pulsations of PY Vulpeculae

Thompson¹,

Clemens²,

Kerkwijk³

et al. 2004

ApJ

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The pulsating white dwarf star PY Vul (G185-32) exhibits pulsation modes with peculiar properties that set it apart from other variable stars in the ZZ Ceti (variable DA white dwarf [DAV]) class. These peculiarities include a low total pulsation amplitude, a mode with bizarre amplitudes in the ultraviolet, and a mode harmonic that exceeds the amplitude of its fundamental. Here we present optical time-series spectroscopy of PY Vul acquired with the Keck II Low Resolution Imaging Spectrograph. Our analysis has revealed that the mode with unusual UV amplitudes also has distinguishing characteristics in the optical. Comparison of its line profile variations to models suggests that this mode has a spherical degree of 4. We show that all the other peculiarities in this star are accounted for by a dominant pulsation mode of l ¼ 4 and propose this hypothesis as a solution to the mysteries of PY Vul.

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Section: Ligg Ht and Velocity Curvv Essupporting

confidence: 52%

Section: About Py Vulmentioning

confidence: 99%

The Peculiar Pulsations of PY Vulpeculae

Thompson¹,

Clemens²,

Kerkwijk³

et al. 2004

ApJ

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“…The chromatic amplitude variation method was used by Robinson et al (1995), Kepler et al (2000), and Castanheira et al (2004). Two stars have their modes clearly identified by the period distribution method: PG 1159-035 (Winget et al 1991) and GD 358 .…”

Section: Observations With Hstmentioning

confidence: 99%

“…Kepler et al (2000) determined for the main periodicities of the DAVs G 185-32, G 226-29 and the DBV PG 1351+489, using a fixed T eff and log g, calculated by other methods. Castanheira et al (2004) determined for G 185-32 modes, keeping all parameters free, using the constraint that solutions for each mode must result in the same T eff and log g. As each periodicity may fit a different value for T eff , we calculated the local minima in χ 2 , which are the possible solutions in the difference between the observed amplitude versus wavelength curve and the models (predicted amplitudes) for each periodicity. Using a normal distribution, we estimated probability densities of that local minimum fit.…”

Section: Periodmentioning

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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“…In addition, time-resolved spectroscopy has been obtained by Thomson et al (2004) with one Keck telescope. Castanheira et al (2004, hereafter CKM) present a preliminary study of G 185-32 based on the WET and HST observations. They tried to discriminate the true pulsation modes from their linear combinations.…”

Section: Introductionmentioning

confidence: 99%

The ZZ Ceti star G 185-32: new insight from asteroseismology

Pech

Vauclair

2006

A&A

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One of the brightest pulsating DA white dwarfs (ZZ Ceti stars), G 185-32, shows 19 periods in its power spectrum, from 71 s to 651 s. Its short periods are among the shortest ones observed in a ZZ Ceti star. The one at 141.9 s shows an amplitude which does not vary with wavelength, in contrast with what the linear theory predicts for = 1 or = 2 non-radial g-modes. The mass and T eff of G 185-32 are well constrained by spectroscopic observations and parallax measurement. The aim of the present paper is to take advantage of this rich observational background to derive the fundamental parameters of the star from asteroseismology. We computed a grid of realistic models for G 185-32 and the periods of their adiabatic = 1 and = 2 non-radial g-modes. We determined the model which fits best the observations. We identify 14 periods as real modes and determine their , k, and m values. We show that the remaining 5 periods are linear combinations.We find that G 185-32 oscillates mostly according to = 2 modes. We present a new hypothesis to account for the peculiar behaviour of the 141.9 s mode's amplitude and suggest that it is a true mode interfering with higher degree modes, involving a possible triplet resonance. We determine the main parameters of G 185-32: its total mass M * = 0.638 (±0.007) M , its hydrogen mass fraction M H = 1.70 (±0.10) × 10 −4 M * , which implies a helium mass fraction of ≈10 −2 M * , its T eff = 12 280 (±)80 K, and estimate its rotation period to be 14.5 h.

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Observations of the Pulsating White Dwarf G 185–32

Cited by 21 publications

References 32 publications

The Peculiar Pulsations of PY Vulpeculae

The Peculiar Pulsations of PY Vulpeculae

HST observations of the pulsating white dwarf GD 358

The ZZ Ceti star G 185-32: new insight from asteroseismology

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