Asteroseismology of the ZZ Ceti star WD 1310+583 using the Transiting Exoplanet Survey Satellite

TL;DR

This work investigates WD 1310+583, a ZZ Ceti white dwarf, by combining TESS photometry with HST/COS spectroscopy to perform a detailed asteroseismic analysis. The star exhibits an unusually rich pulsation spectrum, enabling precise period-spacing and rotational-splitting measurements, though a fully robust period-to-period seismology solution remains elusive due to model degeneracies and potential binarity. The observed period spacing of $ΔΠ_{ℓ=1}≈40.5$ s implies $M_*>≈0.57\;M_⊙$, while tentative asteroseismic modelling favors $M_*=0.632\;M_⊙$ and $T_{ m eff}≈11{,}700$ K, with a distance of $d≈27.8$ pc that is smaller than Gaia’s $d≈30.8$ pc. The study highlights the challenges of reconciling spectroscopic and asteroseismic inferences for DAV stars and demonstrates the power and limitations of TESS in advancing white-dwarf asteroseismology, pointing to the need for improved models and ensemble analyses in future work.

Abstract

Aims. By analysing the light curves of the ZZ Ceti star WD 1310+583, we aim to determine its pulsational frequencies and to give constraints on the main stellar parameters using the tools of asteroseismology. Methods. We performed the Fourier analysis of the TESS light curves of WD 1310+583 and selected the possible pulsational modes. We also used spectroscopic data collected with the Cosmic Origins Spectrograph of the Hubble Space Telescope to give constraints for the asteroseismic analysis. We perform the latter with period-to-period fits using fully evolutionary white dwarf models. Results. The star presented in this paper shows a particularly large number (41) of pulsational frequencies, which provides a potential opportunity for detailed asteroseismic investigations. We found a mean period spacing of ~40.5 seconds, which allows us to state that the stellar mass of WD 1310+583 would be larger than ~0.57 M_Sun. We also attempted an asteroseismological analysis by performing period-to-period fits, but we were unable to find a single statistically significant asteroseismological solution. We adopted a tentative solution consisting of a white dwarf model with M* = 0.632 M_Sun, Teff = 11 702 K, and an asteroseismic distance d = 27.75 +0.17/-0.15 pc, which is significantly smaller than the one predicted by Gaia (d = 30.79 +/- 0.2 pc). We also determined that the rotational period of our target is 1.18 d.

Figures (8)

• Figure 1: The best-fitting solution for a DA+DA two-star model. The left panel shows the fit to the HST COS spectrum and the right panel shows the solution with the photometric data. The synthetic flux from the hotter, pulsating white dwarf is shown in dashed blue while the flux from the cooler companion is shown in dashed green. In the left panel, the reduced spectrum is in grey and in black is the reduced spectrum smoothened across 5 data points. In the right panel, the synthetic flux in each filter is given as black circles and the orange crosses are observed fluxes from the photometric surveys, with the percentage flux residual underneath. The total flux is in red on the left and black on the right for clarity.
• Figure 2: The same as Fig \ref{['fig:AtmosphericSolutionDADA']} but for a DA+DC two-star model. See Sect. \ref{['Joint_fit']} for more details
• Figure 3: Fourier spectra of the different light curve segments. Black horizontal lines indicate the significance levels corresponding to a 0.1% FAP for each dataset. Amplitude variations are clearly visible from sectors to sectors. The vertical lines in each panel correspond to the frequencies listed in Appendix \ref{['app:B']}.
• Figure 4: Fourier spectra of possible rotational frequencies listed in Table \ref{['tabl:rot']}. We note that we utilized pre-whitened Fourier spectra for the plots, as the lower-amplitude peaks become more clearly visible after pre-whitening. Blue horizontal lines indicate the significance levels corresponding to a 0.1% FAP for each dataset.
• Figure 5: Results of the inverse variance (I-V, black), Kolmogorov-Smirnov (K-S, blue), and Fourier Transform (F-T, red) statistical tests applied to a subset of 11 periods marked with asterisks in Appendix \ref{['app:A']}. The three tests point to the existence of a period spacing of $40.58$ s in WD 1310+583, which can be associated to $\ell= 1$ modes. The presence of the subharmonic of this spacing at $\sim 20$ seconds is also apparent.