Oscillating Algol-type eclipsing binaries ( oEA ) are very interesting objects that have three observational features of eclipse , pulsation , and mass transfer .
Direct measurement of their masses and radii from the double-lined radial velocity data and photometric light curves would be the most essential for understanding their evolutionary process and for performing the asteroseismological study .
We present the physical properties of the oEA star XX Cep from high-resolution time-series spectroscopic data .
The effective temperature of the primary star was determined to be 7,946 \pm 240 K by comparing the observed spectra and the Kurucz models .
We detected the absorption lines of the secondary star , which had never been detected in previous studies , and obtained the radial velocities for both components .
With the published BVRI light curves , we determined the absolute parameters for the binary via Wilson-Devinney modeling .
The masses and radii are M _ { 1 } = 2.49 \pm 0.06 M _ { \odot } , M _ { 2 } = 0.38 \pm 0.01 M _ { \odot } , R _ { 1 } = 2.27 \pm 0.02 R _ { \odot } , and R _ { 2 } = 2.43 \pm 0.02 R _ { \odot } , respectively .
The primary star is about 45 \% more massive and 60 \% larger than the zero-age main sequence ( ZAMS ) stars with the same effective temperature .
It is probably because XX Cep has experienced a very different evolutionary process due to mass transfer , contrasting with the normal main sequence stars .
The primary star is located inside the theoretical instability strip of \delta Sct-type stars on HR diagram .
We demonstrated that XX Cep is an oEA star , consisting of a \delta Sct-type pulsating primary component and an evolved secondary companion .