Rotational and pulsational variability in the TESS light curve of HD 27463

Abstract

ABSTRACT The new photometric data on pulsating Ap star HD 27463 obtained recently with the Transiting Exoplanet Survey Satellite (TESS) are analysed to search for variability. Our analysis shows that HD 27463 exhibits two types of photometric variability. The low-frequency variability with the period P  = 2.834 274 ± 0.000 008 d can be explained in terms of axial stellar rotation assuming the oblique magnetic rotator model and presence of surface abundance/brightness spots, while the detected high-frequency variations are characteristics of δ Scuti pulsations. From the analysis of Balmer line profiles visible in two FEROS spectra of HD 27463 we have derived its effective temperature and surface gravity, finding values that are close to those published for this star in the TESS Input Catalogue (TIC). Knowing the rotation period and the v sin i value estimated from the fitting of Balmer line profiles we found that the rotational axis is inclined to the line of sight with an angle of $i=33\pm 8\deg$. Our best-fitting model of the observed pulsation modes results in an overshoot parameter value fov = 0.014 and values of global stellar parameters that are in good agreement with the data reported in the TIC and with the data derived from fitting Balmer line profiles. This model indicates an age of 5.0 ± 0.4 × 108 yr, which corresponds to a core hydrogen fraction of 0.33.