Frequency and photometric analysis of the δ Scuti stars SDSS J231559.32 + 595654.1 and ASAS J080529-1357.5

Abstract

We carried out multi-bandpass BVRI CCD photometric observations for the two δ Scuti stars SDSS J231559.32 + 595654.1 (SDSS23 + 59) and ASAS J080529-1357.5 (ASAS08-13) at Kottamia Astronomical Observatory (KAO). The star SDSS23 + 59 has δ Scuti-type with a low amplitude pulsating variable, and the star ASAS08-13 is classified as a high amplitude δ Scuti-type. The time-series light curve data for each star was analyzed using the discrete Fourier transform (DFT), which revealed a dominant fundamental mode (f0) of oscillation and associated harmonics. The photometric analysis of the two stars suggests SDSS23 + 59 is a star that can pulsate in a short period mode (P = 0.111314d ± 0.000012) with low amplitude (0.101–0.09), and the star ASAS08-13 can pulsate in a short period mode (P = 0.10052247 ± 0.00000281) with high amplitude (0.186–0.168 mag). The nonradial modes for SDSS23 + 59 and radial modes for ASAS08-13 are detected. We calculated new times of maximum light for both stars and combined them with those from other sources (ZTF and AAVSO) to update their corresponding linear ephemerides. The O − C diagram gives us a primary indication that the period of the star is increasing at the rate of (1/P) dP/dt = 3.410(0.006)×10 -10 yr−1 and 2.7321(0.0092)x10-6 yr−1 for SDSS23 + 59 and ASAS08-13 respectively. The physical parameters are calculated, and the positions of the stars on the P-Teff, M−L, M−R, and Teff-log g are investigated.