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)sini = 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 (circle dot), M (2) = 1.101 +/- 0.010 M (circle dot), R (1) = 1.664 +/- 0.010 R (circle dot), R (2) = 1.972 +/- 0.010 R (circle dot), L (1) = 9.67 +/- 0.55 L (circle dot), and L (2) = 2.16 +/- 0.09 L (circle dot).
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 delta Sct variables. The overall results demonstrate that X Tri is an oEA star system consisting of a delta Sct primary and its lobe-filling companion in the semidetached configuration.
