Search for: All records

ABSTRACT G 29 − 38 (TIC 422526868) is one of the brightest (V = 13.1) and closest (d = 17.51 pc) pulsating white dwarfs with a hydrogen-rich atmosphere (DAV/ZZ Ceti class). It was observed by the TESS spacecraft in sectors 42 and 56. The atmosphere of G 29 − 38 is polluted by heavy elements that are expected to sink out of visible layers on short time-scales. The photometric TESS data set spans ∼51 d in total, and from this, we identified 56 significant pulsation frequencies, that include rotational frequency multiplets. In addition, we identified 30 combination frequencies in each sector. The oscillation frequencies that we found are associated with g-mode pulsations, with periods spanning from ∼ 260 to ∼ 1400 s. We identified rotational frequency triplets with a mean separation δνℓ = 1 of 4.67 μHz and a quintuplet with a mean separation δνℓ = 2 of 6.67 μHz, from which we estimated a rotation period of about 1.35 ± 0.1 d. We determined a constant period spacing of 41.20 s for ℓ = 1 modes and 22.58 s for ℓ = 2 modes. We performed period-to-period fit analyses and found an asteroseismological model with M⋆/M⊙ = 0.632 ± 0.03, $$T_{\rm eff}=11\, 635\pm 178$$ K, and log g = 8.048 ± 0.005 (with a hydrogen envelope mass of MH ∼ 5.6 × 10−5M⋆), in good agreement with the values derived from spectroscopy. We obtained an asteroseismic distance of 17.54 pc, which is in excellent agreement with that provided by Gaia (17.51 pc). 

Abstract We explore changes in the adiabatic low-order g-mode pulsation periods of 0.526, 0.560, and 0.729M_⊙carbon–oxygen white dwarf models with helium-dominated envelopes due to the presence, absence, and enhancement of²²Ne in the interior. The observed g-mode pulsation periods of such white dwarfs are typically given to 6−7 significant figures of precision. Usually white dwarf models without²²Ne are fit to the observed periods and other properties. The rms residuals to the ≃150−400 s low-order g-mode periods are typically in the range ofσ_rms≲ 0.3 s, for a fit precision ofσ_rms/P≲ 0.3%. We find average relative period shifts of ΔP/P≃ ±0.5% for the low-order dipole and quadrupole g-mode pulsations within the observed effective temperature window, with the range of ΔP/Pdepending on the specific g-mode, abundance of²²Ne, effective temperature, and the mass of the white dwarf model. This finding suggests a systematic offset may be present in the fitting process of specific white dwarfs when²²Ne is absent. As part of the fitting processes involves adjusting the composition profiles of a white dwarf model, our study on the impact of²²Ne can provide new inferences on the derived interior mass fraction profiles. We encourage routinely including²²Ne mass fraction profiles, informed by stellar evolution models, to future generations of white dwarf model-fitting processes.