Absolute Properties of the Oscillating Eclipsing Algol X Trianguli

Abstract

We report results from the TESS photometric data and new high-resolution spectra of the Algol system X Tri showing short-period pulsations. From the echelle spectra, the radial velocities of the eclipsing pair were measured, and the rotational rate and effective temperature of the primary star were obtained to be v _1 sin i = 84 ± 6 km s ^−1 and T _eff,1 = 7900 ± 110 K, respectively. The synthetic modeling of these observations implies that X Tri is in synchronous rotation and is physically linked to a visual companion TIC 28391715 at a separation of about 6.″5. The absolute parameters of our target star were accurately and directly determined to be M _1 = 2.137 ± 0.018 M _⊙ , M _2 = 1.101 ± 0.010 M _⊙ , R _1 = 1.664 ± 0.010 R _⊙ , R _2 = 1.972 ± 0.010 R _⊙ , L _1 = 9.67 ± 0.55 L _⊙ , and L _2 = 2.16 ± 0.09 L _⊙ . The phase-binned mean light curve was used to remove the binary effect from the observed TESS data. Multifrequency analysis of the residuals revealed 16 significant frequencies, of which the high-frequency signals between 37 day ^−1 and 48 day ^−1 can be considered probable pulsation modes. Their oscillation periods of 0.021−0.027 days and pulsation constants of 0.014−0.018 days are typical values of δ Sct variables. The overall results demonstrate that X Tri is an oEA star system consisting of a δ Sct primary and its lobe-filling companion in the semidetached configuration.

Keywords

• Eclipsing binary stars
• Fundamental parameters of stars
• Stellar oscillations
• Multi-periodic pulsation
• Asteroseismology
• Spectroscopy