Nonradial pulsation of the $δ$ Scuti star UV Trianguli

Abstract

We present the results of a three-year photometric study of the $δ$ Scuti star UV Trianguli. Our data sets consist of 9378 differential measurements in Johnson V together with a few data collected into the Strömgren {\em uvby$β$} system. UV Tri is at least a biperiodic variable. The two best-fitting frequencies, $f_1$=9.3298 d$^{-1}$ and $f_2$=10.8513 d$^{-1}$, are still not the complete set of pulsation frequencies representing the star's light variations. A suspected third frequency might present in the star. Several ``anomalous cycles'' are observed in the light curves. They seem real, but are aperiodic. We derive the colour indices and physical parameters for the variable and conclude that it is a Population I $δ$ Sct star with normal metal abundance ([Me/H]=0.0$\pm$n0.1 dex) evolving on its main sequence stage at an early evolutionary phase before the turn-off point. Finally, we compare the observed oscillation frequencies with theoretical models. The two pulsation modes of UV Tri are likely nonradial to be gravity modes.