Two particular EA-type binaries in the globular cluster ω Centauri

Abstract

We analyzed the B and V light curves of two EA-type binaries V211 and NV358 for the first time using the Wilson-Devinney code. Our analysis shows that V211 is a typical Algol-type binary and NV358 is a well detached binary system. As the two binaries are definite members of ω Centauri due to their proper motion, we estimated their physical parameters, obtaining M1 = 1.13 ± 0.03 M⊙, R1 = 0.98 ± 0.01 R⊙, M2 = 0.33 ± 0.01 M⊙ and R2 = 0.92 ± 0.01 R⊙ for V211; M1 = 1.30±0.05 M⊙, R1 = 1.03±0.01 R⊙, M2 = 0.58±0.02 M⊙ and R2 = 0.78±0.01 R⊙ for NV358. On the color-magnitude diagram of ω Centauri, V211 is located in the faint blue straggler region and its primary component is more massive than a star at the main-sequence turnoff. Therefore, V211 is a blue straggler and was formed by mass transfer from the secondary component to the primary. The age of NV358 is less than 1.93 Gyr, indicating that it is much younger than the first generation of stars in ω Centauri. Like NV364 in ω Centauri, NV358 should be a second-generation binary.