Akademik Veri Yönetim Sistemi
New Astronomy, cilt.126, 2026 (SCI-Expanded, Scopus)
The orbital period variations of four classical Algol-type eclipsing binaries with δ Scuti components were examined using the available minima times. AB Cas, IO UMa and XZ Aql display both an upward parabolic trend and cyclic variation, while the O-C variation of DY Aqr has sinusoidal behavior. The parabolic variations of the three systems reveal an increase in their orbital periods. The O–C analyses of DY Aqr and IO UMa are presented for the first time. For all four systems, cyclic O–C variations were analyzed considering possible third-body effects and magnetic activity cycles. For the XZ Aql and AB Cas systems, a second cyclic variation was identified for the first time after removing parabolic and the first periodic terms. This additional modulation may be attributed either to a fourth unseen companion or to magnetic activity in the cooler secondary components. Among the sample, IO UMa exhibits the highest mass-transfer rate (dM/dt = 11.4 ×10−8 M⊙ yr−1), significantly exceeding the rates of AB Cas (3.6 ×10−8 M⊙ yr−1), and XZ Aql (4.6 ×10−8 M⊙ yr−1). Based on the locations of the studied systems in the r1–q diagram, while the AB Cas and XZ Aql systems are expected to exhibit weak and/or variable accretion structures due to mass transfer, IO UMa may present more prominent evidence of an accretion structure.