Asteroseismic and spectral fitting study of the double DA white dwarf TIC 0030545382

Using TESS observations in 2019, 2021, and 2023 for TIC 0030545382, we extracted frequencies with the Period04 software and reproduced the four intrinsic frequencies identified by Romero et al. The light curve is a typical pulsating white dwarf light curve, without obvious binary occultation information. We evolved about 7.56 million DAV star models using WDEC code and obtained theoretical pulsation periods, which were used to fit the four observed modes. The four observed modes provide weak constraints on the fitting models and five optimal models are derived. Using WDTOOLS module, we performed RV spectral fitting, single white dwarf spectral fitting, and double white dwarfs spectral fitting on three spectra of TIC 0030545382 from SOAR telescope and Gemini South telescope. The fitting of Balmer absorption lines for the three spectra indicates the complexity, diversity, and inconsistency of their RVs, which support the idea that TIC 0030545382 is a binary system. Comprehensive analysis and spectral fitting of double white dwarfs suggest that TIC 0030545382 is a double DA type white dwarfs system, with one non pulsating of T eff around 15600-17500 K and the other pulsating. Combining the asteroseismological results with the trigonometric parallax distance, this DAV WD should have a stellar mass exceeding 0.8 M ⊙ . The inclination angle of the binary orbit to the line of sight direction is likely close but not equal to 90 degrees. The future of this double white dwarf system promises to be highly intriguing, necessitating further spectroscopic observations to obtain more precise physical parameters. • We have extracted six TESS observations of TIC 0030545382 over three years. • We conducted asteroseismic model fitting on TIC 0030545382 using the White Dwarf Evolution Code (WDEC) to evolve a large sample (over 7.56 million) of DAV star models. • We performed spectral fitting for radial velocity, single white dwarf, and double-degenerate white dwarf models on three spectra of TIC 0030545382 using WDTOOLS software, followed by a comprehensive analysis of this star.