CCD Photometry, Light Curve Deconvolution, Period Analysis and Evolutionary Status of the HADS Variable V524 And

摘要

New multi-color BVIc CCD photometric data of V524 And, a pulsating variable long considered to be an SX Phe-type subdwarf system were acquired during 2018. Deconvolution of precise time-series light curve data was accomplished using discrete Fourier transformation and revealed a mean fundamental mode f(0) of oscillation at 10.583 d(-1) along with four other harmonics from 2f(0) to 5f(0). Following successive pre-whitening of each residual signal, no other statistically significant frequency shared by all band-passes was resolved. Potential period changes over time were evaluated using four new times of maximum light derived from the present study along with other values reported in the literature. Photometric data collected during the ROTSE-I (1999) and Super-WASP (2007-2008) surveys combined with CCD-derived V-mag data acquired from the AAVSO archives produced an additional sixty-six times-of-maximum measurements. Corresponding residuals from the observed minus calculated values indicate very little change in the primary pulsation period since 1999. However, a far more interesting finding from this secular analysis suggests an underlying sinusoidal-like variation of P-B = 6.41 yr consistent with a putative binary partner that may be a brown dwarf (M < 0.07 M-circle dot). An investigation with PARSEC models for generating stellar tracks and isochrones provided further insight into the evolutionary status and physical character of V524 And. This intrinsic variable associated with the Galactic disk has an estimated mass around 2 M-circle dot with near-solar metallicity. These characteristics point to V524 And being a Population I HADS with an age approaching 1 Gyr rather than an SX Phe-type variable.