Kepler and TESS Observations of PG 1159-035

Journal Article · 13 September 2022 · The Astrophysical Journal

DOI: https://doi.org/10.3847/1538-4357/ac8871 · OSTI ID:1887325

Oliveira da Rosa, Gabriela; Kepler, S. O. ; Córsico, Alejandro H. ; Costa, J. E. S.; Hermes, J. J. ; Kawaler, S. D. ; Bell, Keaton J. ; Montgomery, M. H. ; Provencal, J. L.; Winget, D. E. ; Handler, G. ; Dunlap, Bart ; Clemens, J. C.; Uzundag, Murat

Abstract PG 1159-035 is the prototype of the PG 1159 hot (pre-)white dwarf pulsators. This important object was observed during the Kepler satellite K2 mission for 69 days in 59 s cadence mode and by the TESS satellite for 25 days in 20 s cadence mode. We present a detailed asteroseismic analysis of those data. We identify a total of 107 frequencies representing 32 ℓ = 1 modes, 27 frequencies representing 12 ℓ = 2 modes, and eight combination frequencies. The combination frequencies and the modes with very high k values represent new detections. The multiplet structure reveals an average splitting of 4.0 ± 0.4 μ Hz for ℓ = 1 and 6.8 ± 0.2 μ Hz for ℓ = 2, indicating a rotation period of 1.4 ± 0.1 days in the region of period formation. In the Fourier transform of the light curve, we find a significant peak at 8.904 ± 0.003 μ Hz suggesting a surface rotation period of 1.299 ± 0.002 days. We also present evidence that the observed periods change on timescales shorter than those predicted by current evolutionary models. Our asteroseismic analysis finds an average period spacing for ℓ = 1 of 21.28 ± 0.02 s. The ℓ = 2 modes have a mean spacing of 12.97 ± 0.4 s. We performed a detailed asteroseismic fit by comparing the observed periods with those of evolutionary models. The best-fit model has T _eff = 129, 600 ± 11 100 K, M _* = 0.565 ± 0.024 M _⊙ , and $\log g={7.41}_{-0.54}^{+0.38}$ , within the uncertainties of the spectroscopic determinations. We argue for future improvements in the current models, e.g., on the overshooting in the He-burning stage, as the best-fit model does not predict excitation for all of the pulsations detected in PG 1159-035.

• Research Organization: University of Texas, Austin, TX (United States)
• Sponsoring Organization: Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT); Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES); Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS); National Aeronautics and Space Administration (NASA); National Council for Scientific and Technological Development (CNPq); National Science Centre (NCN); National Science Foundation (NSF); USDOE; USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: NA0003843; SC0010623
• OSTI ID: 1887325
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 2 Vol. 936; ISSN 0004-637X
• Publisher: American Astronomical SocietyCopyright Statement
• Country of Publication: United States
• Language: English