Photometric and Spectroscopic Analysis of the SX Phe Star BL Cam

TL;DR

This study combines photometric and spectroscopic data to analyze the pulsation and evolutionary changes of the SX Phe star BL Cam, revealing period variations and physical parameters consistent with stellar evolution models.

Contribution

It provides new observational data and analysis of BL Cam's pulsation modes, period changes, and physical parameters, enhancing understanding of SX Phe star evolution.

Findings

Detected fundamental mode with two harmonics

Established period decrease and evolutionary period change

Derived physical parameters consistent with stellar models

Abstract

In the present paper, we report the photometric and spectroscopic observations obtained by the 1.88 m telescope at the Kottamia astronomical observatory of the pulsating star BL Cam. Fourier analysis of the light curves reveals that the fundamental mode has two harmonics. The O-C method is used to establish the period changes. So far, the analysis has been very successful in mapping the pulsation amplitude of the star across the instability strip. By using the formalism of Eddington and Plakidis (1929), we found significant results and strong indications of the evolutionary period change. A total of 55 new maximum light timings are reported. New values of (1/P) dP/dt are estimated using the O-C diagram based on all newly obtained times of maximum light combined with those taken from the literature, assuming the periods are decreasing and changing smoothly. To compute the effective temperature and surface gravity of the star, we performed model atmosphere analysis on its spectra. The physical parameters of the star are calculated and compared with the evolutionary models.